1 Nervous, Sensory, and Motor SystemsChapter 27 Nervous, Sensory, and Motor Systems

2 Biology and Society: Beyond Human ExperienceMany animals perceive the world in ways we cannot. Bats and porpoises generate ultrasonic sounds in echolocation to Detect echoes Determine the size, shape, location, speed, and direction of objects in the environment © 2010 Pearson Education, Inc.

3 Figure 27.00 Guided by echoes

4 Many species of fish use electroreception to generate weak electric fields that reveal objects in low-visibility environments. Migratory birds, fish, turtles, amphibians, and bees use magnetoreception to Detect magnetic fields Orient their movements relative to Earth’s magnetic fields

5 AN OVERVIEW OF ANIMAL NERVOUS SYSTEMSThe nervous system forms a communication and coordination network throughout an animal’s body. Neurons are nerve cells specialized for carrying electrical signals from one part of the body to another. Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

6 Organization of Nervous SystemsThe nervous system of most animals has two main divisions. The central nervous system (CNS) consists of the brain and spinal cord (in vertebrates). The peripheral nervous system (PNS) consists of mostly of nerves that carry signals into and out of the CNS. Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

7 A nerve is a communication line made from cable-like bundles of neuron fibers.Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

8 Effectors perform the body’s responses to motor output.The three interconnected functions of the nervous system are carried out by three types of neurons: Sensory neurons function in sensory input Interneurons integrate information Motor neurons function in motor output Effectors perform the body’s responses to motor output. Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

9 Peripheral nervous system (PNS) Central nervous system (CNS)SENSORY INPUT Sensory neuron INTEGRATION Sensory receptor Interneuron MOTOR OUTPUT Figure 27.1 Organization of a nervous system Motor neuron Brain and spinal cord Effector cells Peripheral nervous system (PNS) Central nervous system (CNS) Figure 27.1

10 Neurons Neurons Are the functional units of the nervous systemVary widely in shape Share some common features Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

11 Signal direction Dendrites Cell body Axon Signal pathway SynapticFigure 27.2 Structure of a motor neuron Synaptic terminals Supporting cell Nucleus Myelin sheath Figure 27.2

12 The cell body houses The nucleus Other organellesStudent Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

13 Two types of extensions project from the cell body:Dendrites, which: Receive incoming messages from other cells Convey the information toward the cell body Axons, which transmit signals toward another neuron or toward an effector Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

14 Supporting cells The myelin sheathOutnumber neurons by as many as 50 to 1 Protect, insulate, and reinforce the neurons The myelin sheath Forms an insulating material around an axon Helps increase the speed of the electrical signal Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

15 An axon ends in a cluster of branches, each with a bulb-like synaptic terminal that relays signals to Another neuron or An effector Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

16 Signal direction Dendrites Cell body Axon Signal pathway SynapticFigure 27.2 Structure of a motor neuron Synaptic terminals Supporting cell Nucleus Myelin sheath Figure 27.2

17 Sending a Signal through a NeuronA resting neuron has potential energy that can be put to work to send nerve signals from one part of the body to another. This difference in charge (voltage) across the plasma membrane of a resting neuron is the resting potential. Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

18 The Action Potential A stimulus is any factor that causes a nerve signal to be generated. A stimulus of sufficient strength can trigger an action potential, a nerve signal that carries information along a neuron. Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences. Blast Animation: Action Potential Animation: Action Potential Animation: Resting Potential

19 Figure 27.3-1 Neuron interiorFigure 27.3 Generation of an action potential (Step 1) Figure

20 Figure 27.3-2 Neuron interior  Figure 27.3 Generation of an action potential (Step 2) Figure

21 Figure 27.3-3 Neuron interior   Figure 27.3 Generation of an action potential (Step 3)  Figure

22 Figure 27.3-4 Neuron interior   Figure 27.3 Generation of an action potential (Step 4)    Figure

23 Propagation of the SignalAn action potential is a localized electrical event. To function as a nerve signal over a distance, this local event must be passed along the neuron. Action potential propagation is like a “domino effect” along a neuron. Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

24 Axon Action potential   Figure 27.4 Propagation of an action potential along an axon (Step 1) Figure

25 Axon Action potential   Action potential    Figure 27.4 Propagation of an action potential along an axon (Step 2)  Figure

26 Axon Action potential   Action potential    Figure 27.4 Propagation of an action potential along an axon (Step 3)  Action potential   Figure

27 Action potentials are All-or-none eventsThe same no matter how strong or weak the stimulus that triggers them Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

28 Passing a Signal from a Neuron to a Receiving CellA synapse is a relay point Between two neurons or Between a neuron and an effector cell Synapses come in two varieties: Electrical Chemical Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

29 Chemical synapses Have a narrow gap, the synaptic cleft, separating a synaptic terminal of the sending neuron from the receiving cell Rely on neurotransmitters, chemicals that carry information from one nerve cell to another kind of cell Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences. Blast Animation: Signal Amplification in Neurons Animation: Synapse Blast Animation: Signal Transmission at Synapses

30 Figure 27.5 Figure 27.5 Neuron communication at a synaptic cleftterminal of sending neuron Dendrite of receiving neuron SYNAPSE Sending neuron Vesicles Action potential arrives. Neurotransmitter Synaptic terminal Receptor Ions Vesicle fuses with plasma membrane. Neurotransmitter is released into synaptic cleft. Figure 27.5 Neuron communication at a synaptic cleft Synaptic cleft Ion channel opens and triggers or inhibits a new action potential. Ion channel closes. Neurotransmitter is broken down and released. Neurotransmitter binds to receptor. Receiving neuron Neurotransmitter molecules Ion channels Figure 27.5

31 SYNAPSE Sending neuron Action Vesicles potential arrives. Synapticterminal Vesicle fuses with plasma membrane. Neurotransmitter is released into synaptic cleft. Figure 27.5a Neuron communication at a synaptic cleft Synaptic cleft Neurotransmitter binds to receptor. Receiving neuron Neurotransmitter molecules Ion channels Figure 27.5a

32 Neurotransmitter Receptor Ions Ion channel opens andFigure 27.5b Neuron communication at a synaptic cleft Ion channel opens and triggers or inhibits a new action potential. Ion channel closes. Neurotransmitter is broken down and released. Figure 27.5b

33 Chemical synapses can process extremely complex information. A neuron may receive input from hundreds of other neurons via thousands of synaptic terminals. Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

34 Figure 27.6 Dendrites Myelin sheath Receiving cell body Axon Synapticterminals Figure 27.6 A neuron's multiple synaptic inputs SEM Figure 27.6

35 Dendrites Myelin sheath Receiving cell body Axon Synaptic terminalsFigure 27.6a A neuron's multiple synaptic inputs Axon Synaptic terminals Figure 27.6a

36 Synaptic terminals SEM Figure 27.6bFigure 27.6b A neuron's multiple synaptic inputs SEM Figure 27.6b

37 Neurotransmitters A variety of small molecules can act as neurotransmitters: Amines, derived from amino acids that affect sleep, mood, attention, and learning Peptides, short chains of amino acids that include endorphins, which decrease pain perception Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

38 Drugs and the Brain Many drugs, such as caffeine, nicotine, and alcohol, act at synapses by increasing or decreasing the normal effect of neurotransmitters. Prescription drugs used to treat psychological disorders alter the effects of neurotransmitters. Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar assumptions. Students that read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s). 2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees” Regularly relate the three fundamental functions of the nervous system, sensory input, integration, and motor output, to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure. 3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will permit easy reference to check an action of a drug. Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation. 2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog-like item and bring along three hot dog buns. 3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick clear demonstration. As noted in the text, potential electrical energy can be stored in a battery. 4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments. 5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium. 6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency. 7. Students might better understand the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person might reach a “threshold” and be stimulated enough to get up and turn it off. 8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus? 9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry). 10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.” 11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage. 12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience. 13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide your medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street? 14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

39 THE HUMAN NERVOUS SYSTEM: A CLOSER LOOKAlthough there is remarkable uniformity in the way nerve cells function, there is great variety in how nervous systems as a whole are organized. Vertebrate nervous systems are diverse in Structure Level of sophistication Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense. © 2010 Pearson Education, Inc.

40 The Central Nervous SystemVertebrate central nervous systems Integrate information coming from the senses Transmit signals that produce responses Consist of the Brain, the master control center of the nervous system Spinal cord, a jellylike bundle of nerve fibers inside the spinal column Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

41 Brain Central nervous system (CNS) Peripheral nervous Spinal cordsystem (PNS) Spinal cord Figure 27.7 A vertebrate nervous system (back view) Figure 27.7

42 The brain and spinal cordContain spaces Are filled with cerebrospinal fluid, a liquid that Cushions the CNS Helps supply the CNS with nutrients, hormones, and white blood cells Also protecting the brain and spinal cord are layers of connective tissues called meninges. Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

43 Spinal cord (cross section)Brain Cerebrospinal fluid Meninges Figure 27.8 Fluid-filled spaces of the vertebrate CNS Spinal cord (cross section) Spinal cord Figure 27.8

44 The Peripheral Nervous SystemThe vertebrate peripheral nervous system is divided into two functional components: The somatic nervous system The autonomic nervous system Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

45 Somatic nervous system Autonomic nervous systemPERIPHERAL NERVOUS SYSTEM Somatic nervous system (voluntary) Autonomic nervous system (involuntary)  Parasympathetic division (rest and digest)  Sympathetic division (fight or flight) Figure 27.9 Functional divisions of the vertebrate PNS LM Voluntary leg muscles Involuntary heart muscle Figure 27.9

46 Voluntary leg muscles Figure 27.9aFigure 27.9a Functional divisions of the vertebrate PNS Voluntary leg muscles Figure 27.9a

47 Involuntary heart muscleFigure 27.9b Functional divisions of the vertebrate PNS LM Involuntary heart muscle Figure 27.9b

48 The somatic nervous systemCarries signals to and from skeletal muscles Mainly responds to external stimuli Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

49 The autonomic nervous systemRegulates the internal environment Controls Smooth and cardiac muscles Organs and glands of the digestive, cardiovascular, excretory, and endocrine systems Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

50 The autonomic nervous system contains two sets of neurons with opposing effects on most organs:The parasympathetic division primes the body for digesting food and resting. The sympathetic division prepares the body for intense, energy-consuming activities. Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

51 The Human Brain The brain, the most sophisticated computer, consists of Up to 100 billion intricately organized neurons Many more supporting cells Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

52 The brain is divided into three regions:The hindbrain The midbrain The forebrain Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

53 Cerebrum Cerebral cortex Forebrain Thalamus Hypothalamus Pituitarygland Figure The main parts of the human brain Midbrain Pons Spinal cord Medulla oblongata Hindbrain Cerebellum Figure 27.10

54 Table 27.1 Structure and Function of the Human Brain

55 The brainstem Consists of the hindbrain (medulla oblongata and pons) and the midbrain Serves as a sensory filter, selecting which information reaches higher brain centers The cerebellum, another part of the hindbrain, is a planning center for body movements. Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

56 The forebrain contains the most sophisticated integrating centers in the brain:The thalamus, which relays information to the cerebral cortex The hypothalamus, with many regulatory functions The cerebrum, the largest and most sophisticated part of the brain Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

57 The Cerebral Cortex The cerebrum consists of right and left cerebral hemispheres interconnected by the corpus callosum. Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

58 Left cerebral Right cerebral hemisphere hemisphere Corpus callosumThalamus Figure A rear view of the brain Cerebellum Medulla oblongata Figure 27.11

59 The cerebral cortex Is a highly folded layer of tissue that forms the surface of the cerebrum Helps produce our most distinctive human traits Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

60 The right and left cerebral hemispheresHave four lobes Are specialized for different mental tasks in a phenomenon known as lateralization Higher mental activities occur in association areas of the brain. Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

61 Frontal lobe Parietal lobe cortex So sensory ma to otor cortex Massociation area Somatosensory association area Speech Taste Reading Speech Hearing Visual association area Smell Auditory association area Figure Functional areas of the cerebrum's left hemisphere Vision Temporal lobe Occipital lobe Figure 27.12

62 Evidence from brain surgery patients indicates that patterns of lateralization are not fixed.Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

63 Figure 27.13 Hemispherectomy

64 Brain Trauma In 1848, a railroad accident to a man named Phineas GagePropelled a three-foot-long spike through his head but Caused significant changes in his personality. Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense. © 2010 Pearson Education, Inc.

65 Figure 27.14 Phineas Gage's accident

66 Neurological DisordersNeurological disorders can also affect brain function. Major depression is extreme and persistent sadness and loss of interest in pleasurable activities. Bipolar disorder involves extreme mood swings. Alzheimer’s disease causes mental deterioration. Student Misconceptions and Concerns 1. Popular media often suggests that lateralization is a fixed human trait. Certain people are “left-brained” while others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity. 2. Your students might suspect that the brain of humans is fundamentally different from the brain of other animals. They might expect that humans have brain regions not found elsewhere. Instead, the human brain reflects a remodeling of the same basic brain structure found in other mammals and vertebrates in general. 3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion. Teaching Tips 1. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website At the time of the writing of this book, the U.S. population was about 310 million people. 2. Challenge your students to explain why their brains are located at one end of the body. You might wish to point out that the main sensory organs of the body are also concentrated in this region. At the end of the discussion, point out that, for a similar reason, airline pilots sit in the front of the plane. 3. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses are not quickly reversed. Students might recall how long it took to calm down when they or others have been extremely upset or nervous. When trying to calm someone down, it is best to separate him or her from the stress and to allow him or her time. Taking a long walk with them provides mild exercise, a retreat from the situation, and emotional comfort that makes biological sense.

67 Area of decreased brain activity Depressed person Healthy personFigure Brain activity in a depressed person and healthy person Healthy person Figure 27.15

68 Area of decreased brain activity Depressed person Figure 27.15aFigure 27.15a Brain activity in a depressed person Area of decreased brain activity Depressed person Figure 27.15a

69 Healthy person Figure 27.15bFigure 27.15b Brain activity in a healthy person Healthy person Figure 27.15b

70 THE SENSES Sensory structures Gather information Pass it on to the CNSStudent Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

71 Sensory Input Sensory input is the process of using receptors toSense the environment Send information about it to the CNS to be integrated and acted upon Sensory transduction is the conversion of a stimulus signal to an electrical signal by a sensory receptor cell. Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

72 Sensory Transduction Receptor potentialsAre changes in membrane potentials caused by sensory stimuli Vary in intensity, depending on the strength of the stimulus Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

73 Figure 27.16 Receptor Sugar Membrane molecule of sensory (stimulus)receptor cell Signal transduction pathway Ion channels Sugar molecule Sensory receptor cell Taste bud Ion Sensory receptor cells Receptor potential Figure Sensory transduction in a human taste bud Neurotransmitter Sensory neuron Sensory neuron Action potential (to brain) Figure 27.16

74 Figure 27.16a Receptor Sugar Membrane molecule of sensory (stimulus)receptor cell Sugar molecule Signal transduction pathway Taste bud Sensory receptor cells Ion channels Sensory receptor cell Ion Receptor potential Figure 27.16a Sensory transduction in a human taste bud Sensory neuron Neurotransmitter Sensory neuron Action potential (to brain) Figure 27.16a

75 Sensory adaptation Causes some sensory receptors to be less sensitive when they are stimulated repeatedly Keeps the body from continuously reacting to normal background stimuli Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

76 Types of Sensory ReceptorsSensory receptors can be grouped into five categories, which work in various combinations to produce the five human senses. A section of human skin reveals why the surface of our body is sensitive to such a variety of stimuli. Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

77 Figure 27.17 Heat Light touch Pain Cold (Hair) Epidermis DermisFigure Sensory receptors in the human skin Nerve to CNS Hair movement Strong pressure Figure 27.17

78 Pain receptors respond to stimuli causing injury or disease. Thermoreceptors detect heat or cold. Mechanoreceptors are stimulated by various forms of mechanical energy. Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

79 Chemoreceptors respond to chemicals in the external environment or body fluids.Electromagnetic receptors are sensitive to energy of various wavelengths, including light. Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

80 Vision Human eyes are able to Detect a multitude of colorsForm images of faraway objects Respond to minute amounts of light energy Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

81 Structure of the Human EyeThe human eye consists of A tough outer covering, the sclera A transparent cornea in front of the lens An iris with a center opening, the pupil The retina, at the back of the eyeball, where photoreceptors respond to light The optic nerve connects the retina to the brain Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

82 Two fluid-filled chambers make up the bulk of the eye.The large chamber is filled with vitreous humor. The small chamber contains aqueous humor. Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

83 Choroid Sclera Retina Muscle Ligament Cornea Iris Optic nerve PupilAqueous humor Figure The human eye Lens Vitreous humor Blind spot Figure 27.18

84 Function of the Human EyeThe iris Regulates the size of the pupil Lets light shine onto the lens The lens of the eye changes shape and refracts light, which focuses light onto the retina. Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class. Animation: Near and Distance Vision

85 Near vision Muscle contracted Choroid Ligaments slacken RetinaLight from a near object Lens Distance vision Muscle relaxed Figure How the lens of the eye focuses light Ligaments pull on lens Light from a distant object Figure 27.19

86 Photoreceptors The human retina contains two types of photoreceptors.Rods: Are extremely sensitive to light Perceive only shades of gray Are distributed at the outer edges of the retina Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

87 Cones: Are less sensitive to light Perceive colors Are distributed at the center of focus on the retina Rods and cones detect light using an array of membranous disks containing visual pigments. Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

88 containing visual pigments Cell bodyRod Membranous disks containing visual pigments Cell body Cone Figure Photoreceptor cells Synaptic terminals Figure 27.20

89 Rods and cones are stimulus transducers thatAbsorb light Generate receptor potentials Other retinal neurons Integrate these receptor potentials Generate action potentials that travel along the optic nerve to the brain Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

90 Figure 27.21 Retina Neurons Photoreceptors Cone Rod Optic nerve fibersFigure The vision pathway from light source to optic nerve Optic nerve To brain Figure 27.21

91 Vision Problems and CorrectionsThe most common visual problems are Nearsightedness, the inability to focus on distant objects Farsightedness, the inability to focus on near objects Astigmatism, blurred vision caused by a misshapen lens or cornea Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

92 Figure 27.22 Shape of normal eyeball Shape of normal eyeball LensRetina Point of focus Point of focus Corrective lens Corrective lens Figure A nearsighted eye and a farsighted eye Point of focus Point of focus (a) A nearsighted eye (eyeball too long) (b) A farsighted eye (eyeball too short) Figure 27.22

93 (a) A nearsighted eye (eyeball too long)Shape of normal eyeball Lens Retina Point of focus Corrective lens Point of focus Figure 27.22a A nearsighted eye and a farsighted eye (a) A nearsighted eye (eyeball too long) Figure 27.22a

94 (b) A farsighted eye (eyeball too short)Shape of normal eyeball Point of focus Corrective lens Figure 27.22b A nearsighted eye and a farsighted eye Point of focus (b) A farsighted eye (eyeball too short) Figure 27.22b

95 Hearing The Structure of the Human EarThe ear is composed of The outer ear The middle ear The inner ear Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

96 (b) The middle and inner earsOuter ear Middle ear Pinna Auditory canal Stirrup Eardrum Skull bones Anvil Auditory nerve, to brain Eustachian tube (a) Ear structure Hammer Figure An overview of the human ear Eardrum Eustachian tube Cochlea (b) The middle and inner ears Figure 27.23

97 Outer ear Middle ear Inner ear Pinna Auditory canal EardrumFig a Outer ear Middle ear Inner ear Figure 27.23a An overview of the human ear Pinna Auditory canal Eardrum Eustachian tube (a) Ear structure Figure 27.23a

98 The outer ear Consists of the pinna and the auditory canalCollects sound waves Passes sound waves to the eardrum, a sheet of tissue that separates the outer ear from the middle ear Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

99 In the middle ear, the vibrating eardrum passes the sound waves to three small bones that relay the sound to the inner ear. The Eustachian tube Conducts air between the middle ear and back of the throat Allows air pressure to stay equal on either side of the eardrum Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

100 (b) The middle and inner earsStirrup Skull bones Hammer Anvil Auditory nerve, to brain Figure 27.23b An overview of the human ear Eardrum Cochlea Eustachian tube (b) The middle and inner ears Figure 27.23b

101 One of the channels, the cochlea, contains the organ of Corti, whichThe inner ear consists of fluid-filled channels in the bones of the skull. One of the channels, the cochlea, contains the organ of Corti, which Is the actual hearing organ Includes hair cells, the receptor cells of the ear Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

102 To auditory nerve and brainCross section through cochlea Bone Fluid Auditory nerve Organ of Corti Overlying membrane Hair cells Supporting cells Figure The organ of Corti, within the cochlea Sensory neurons Basilar membrane To auditory nerve and brain Figure 27.24

103 Cross section through cochlea Bone Fluid Auditory nerve Organ of CortiFigure 27.24a The organ of Corti, within the cochlea Auditory nerve Organ of Corti Figure 27.24a

104 To auditory nerve and brainOverlying membrane Hair cells Supporting cells Sensory neurons Figure 27.24b The organ of Corti, within the cochlea Basilar membrane To auditory nerve and brain Figure 27.24b

105 Function of the Human EarWhen we hear, sound waves Are collected by the outer ear Are transmitted indirectly to the cochlea, which causes Hair cells in the organ of Corti to bend Nerve cells to send signals to the brain Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

106 Figure 27.25 Outer ear Middle ear Inner ear Auditory canal Ear- drumHammer, anvil, stirrup Pinna Cochlea Pressure Figure The route of sound waves through the ear Time Organ of Corti stimulated Amplitude Concentration in middle ear One vibration Figure 27.25

107 Louder sounds cause Greater movement of the hair cellsMore action potentials Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

108 Hearing Problems Deafness, the loss of hearing, can be caused byMiddle ear infections Injury, such as a ruptured eardrum Overexposure to loud noises Student Misconceptions and Concerns 1. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. CD players, DVD recordings, and iPod players rely upon electronic storage and signal conversions to store and generate sounds and images. 2. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.) Teaching Tips 1. The natural tendency to wonder about our world seems to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences. Perhaps you might have your class ask questions about their sensory experiences on 3x5 cards, which you can selectively answer later, and as time permits. The following tips include some examples. 2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain. 3. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.” 4. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure. 5. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose. 6. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots. The more dots to paint the picture, the clearer the image. 7. Another common eye problem is cataracts, a clouding of the lens of the eye. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce the exposure to UV light. 8. Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This pigment prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer, and instead reflects off red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red colored blood, and make the pupils appear red. 9. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax. 10. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class. 11. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. The concept of triangulation may not be understood by your students. It might be helpful to explain this phenomenon and the advantages of using two ears noted in #12 directly below. 12. Consider asking your students why each of us has two ears? In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source. Of course, there are exceptions. 13. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones and cartilage. These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air. 14. The range of human hearing and the effect of age can be demonstrated by a popular high-pitched ring tone. Searching “high pitched ring tone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ring tone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear. 15. MP3 players and other players have increased our ability to damage our hearing. In addition, listening to loud music while actively exercising outdoors can interfere with the detection of danger or vital communication. Consider discussing these important safety concerns with your class.

109 MOTOR SYSTEMS MovementIs one of the most distinctive features of animals Relies upon an interplay of organ systems The nervous system issues commands to the muscular system. The muscular system exerts the forces that make animals move by acting on the skeletal system. Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

110 The Skeletal System The skeletal system provides Anchoring SupportProtection of internal organs Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

111 Organization of the Human SkeletonAll vertebrates have an endoskeleton, situated among soft tissues, and consisting of Bones, hard supporting elements Cartilage at points of flexibility Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

112 Figure 27.26 Skull Shoulder girdle Clavicle Scapula Sternum RibsHumerus Vertebra Ulna Radius Pelvic girdle Carpals Metacarpals Phalanges (curled under) Figure The human endoskeleton Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges Figure 27.26

113 Skull Shoulder girdle Clavicle Scapula Sternum Ribs Humerus VertebraUlna Radius Figure 27.26a The human endoskeleton Pelvic girdle Carpals Metacarpals Phalanges (curled under) Figure 27.26a

114 Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges Figure 27.26bFigure 27.26b The human endoskeleton Fibula Tarsals Metatarsals Phalanges Figure 27.26b

115 The appendicular skeleton is made up of the bones of theThe axial skeleton Supports the axis of the body Includes the skull, vertebral column, and rib cage The appendicular skeleton is made up of the bones of the Limbs Shoulders Pelvis Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

116 Much of the versatility of our skeleton comes from three types of movable joints:Ball-and-socket joints in the shoulder and hip Hinge joints that permit movement in a single plane Pivot joints that allow rotation The bones of the skeleton are held together at movable joints by strong fibrous ligaments. Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

117 (example: elbow flexing) (example: elbow rotation)JOINTS Ball-and-socket (example: shoulder) Hinge (example: elbow flexing) Pivot (example: elbow rotation) Head of humerus Humerus Ulna Radius Figure Three kinds of joints Ulna Scapula Figure 27.27

118 Ball-and-socket (example: shoulder)Head of humerus Scapula Figure 27.27a Three kinds of joints Figure 27.27a

119 (example: elbow flexing)Hinge (example: elbow flexing) Humerus Figure 27.27b Three kinds of joints Ulna Figure 27.27b

120 (example: elbow rotation)Pivot (example: elbow rotation) Figure 27.27c Three kinds of joints Radius Ulna Figure 27.27c

121 The Structure of Bones BonesAre covered with a connective tissue membrane Have cartilage at their ends that cushions the joints Are served by blood vessels and nerves Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

122 Cartilage Spongy bone (contains red bone marrow) Compact boneCentral cavity Yellow bone marrow Figure The structure of an arm bone Fibrous connective tissue Blood vessels Cartilage Figure 27.28

123 The central cavity of a long bone contains yellow bone marrow, which is mostly stored fat.The end of a long bone contains red bone marrow, a specialized tissue that produces blood cells. Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

124 Skeletal Diseases and InjuriesThe human skeleton Is quite strong and provides reliable support, but Is susceptible to disease and injury Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

125 Arthritis Rheumatoid arthritis Is an inflammation of the jointsAffects one out of every seven people in the United States Rheumatoid arthritis Is an autoimmune disease Usually begins between ages 40 and 50 Affects more women than men Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

126 Osteoporosis Makes bones thinner and more porousIs most common in women after menopause Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

127 Bones are rigid but not inflexible. If a force applied to a bone exceeds its capacity to bend, the result is a broken bone or fracture. The treatment of a fracture involves Putting the bone back into its natural shape Immobilizing it until the body’s natural bone-building cells can repair the fracture Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

128 Figure Broken bones Figure 27.29

129 The Muscular System The muscular system is made of all the skeletal muscles in the body. Skeletal muscles Are attached to the skeleton Pull on bones to produce movements Tendons connect muscles to bones. Antagonistic pairs of muscles produce opposite movements. Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

130 Biceps relaxed Biceps contracted Triceps relaxed Triceps contractedFigure Antagonistic action of muscles in the human arm Triceps relaxed Triceps contracted Tendon Figure 27.30

131 The Cellular Basis of Muscle ContractionSkeletal muscle is made up of a hierarchy of smaller and smaller parallel strands. Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences. Blast Animation: Anatomy of Muscle

132 Figure 27.31 Figure 27.31 The contractile apparatus of skeletal muscleBundle of muscle fibers Nuclei Single muscle fiber (cell) Myofibril Light band Light band Dark band Sarcomere Figure The contractile apparatus of skeletal muscle TEM Light band Dark band Light band Thick filaments (myosin) Thin filaments (actin) Sarcomere Figure 27.31

133 Figure 27.31a Muscle Bundle of muscle fibers NucleiSingle muscle fiber (cell) Figure 27.31a The contractile apparatus of skeletal muscle Myofibril Light band Light band Dark band Figure 27.31a

134 Figure 27.31b Myofibril Light band Light band Dark band SarcomereTEM Figure 27.31b The contractile apparatus of skeletal muscle Light band Light band Dark band Thick filaments (myosin) Thin filaments (actin) Sarcomere Figure 27.31b

135 Each skeletal muscle cell, or fiberContains bundles of myofibrils Is called striated, because the myofibrils exhibit alternating light and dark bands when viewed with a light microscope A sarcomere Is the region between two dark, narrow lines called Z lines Is the functional unit of muscle contraction Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

136 A myofibril is composed of two kinds of filaments:Thin filaments, made mostly of the protein actin Thick filaments, made mostly of the protein myosin A sarcomere contracts when its thin filaments slide across its thick filaments. Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

137 Sarcomere Dark band Relaxed muscle Contracting muscle Fully contractedFigure The sliding-filament model of muscle contraction Fully contracted muscle Figure 27.32

138 In the sliding-filament model, the key events are the binding betweenParts (called heads) of the myosin molecules in the thick filaments Specific sites on actin molecules in the thin filaments Contraction requires energy supplied by ATP. Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

139 Figure 27.33-1 Figure 27.33 The mechanism of filament sliding (Step 1)Thick filament (myosin) ATP Myosin head (low-energy configuration) Thin filament (actin) ATP binds to a myosin head, which is then released from an actin filament. Figure The mechanism of filament sliding (Step 1) Figure

140 Figure 27.33-2 Figure 27.33 The mechanism of filament sliding (Step 2)Thick filament (myosin) ATP Myosin head (low-energy configuration) Thin filament (actin) ATP binds to a myosin head, which is then released from an actin filament. Myosin head (high-energy configuration) ATP ADP + P The breakdown of ATP cocks the myosin head. Figure The mechanism of filament sliding (Step 2) Figure

141 Figure 27.33-3 Figure 27.33 The mechanism of filament sliding (Step 3)Thick filament (myosin) ATP Myosin head (low-energy configuration) Thin filament (actin) ATP binds to a myosin head, which is then released from an actin filament. Myosin head (high-energy configuration) ATP ADP + P The breakdown of ATP cocks the myosin head. Figure The mechanism of filament sliding (Step 3) The myosin head attaches to an actin binding site. Figure

142 Figure 27.33-4 Figure 27.33 The mechanism of filament sliding (Step 4)Thick filament (myosin) ATP Myosin head (low-energy configuration) Thin filament (actin) ATP binds to a myosin head, which is then released from an actin filament. Myosin head (high-energy configuration) ATP ADP + P The breakdown of ATP cocks the myosin head. Figure The mechanism of filament sliding (Step 4) The myosin head attaches to an actin binding site. The power stroke slides the actin (thin) filament toward the center of the sarcomere. As long as ATP is available, the process can be repeated until the muscle is fully contracted. Figure

143 ATP binds to a myosin head, which is then released Thick filament (myosin) Myosin head (low-energy configuration) ATP Thin filament (actin) ATP binds to a myosin head, which is then released from an actin filament. Figure 27.33a The mechanism of filament sliding Myosin head (high-energy configuration) ATP ADP + P The breakdown of ATP cocks the myosin head. Figure 27.33a

144 Figure 27.33b The myosin head attaches to an actin binding site.Figure 27.33b The mechanism of filament sliding The power stroke slides the actin (thin) filament toward the center of the sarcomere. As long as ATP is available, the process can be repeated until the muscle is fully contracted. Figure 27.33b

145 Motor Neurons: Control of Muscle ContractionCan branch to a number of muscle fibers Stimulate muscles to contract A neuromuscular junction is the connection between A motor neuron Muscle fibers associated with that neuron Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

146 A motor unit consists ofA neuron All the muscle fibers it controls Motor units may consist of Just one muscle fiber or Up to hundreds of muscle fibers The strength of a muscle contraction depends on the number of motor units activated. Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

147 Motor Spinal cord Motor unit 1 unit 2 Nerve Motor neuron Motorcell body Motor neuron axon Nuclei Neuromuscular junctions Muscle fibers (cells) Muscle Figure The relationship between motor neurons and muscle fibers Tendon Bone Figure 27.34

148 The Process of Science: How Do New Sense Arise?Observation: Two species of electric fish use special ion channel proteins in muscle cells to generate electric fields. Question: Did different ion channel proteins evolve in these two species? Hypothesis: Ion channel genes of the two electric species had mutated in unique ways. Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences. © 2010 Pearson Education, Inc.

149 Experiment: The DNA sequence of the genes in the two electric fish was determined and compared to a closely related but non-electric fish. Results: A single ion channel gene duplicated in the common ancestor, into forms a and b. The a form mutated differently in the two electric fish species. The b form retained its muscle functions in electric and non-electric fishes. Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

150 South American speciesAfrican species South American species Electric fish Electric fish Nonelectric fish Location of gene function Muscle Gene b b a and b Figure Duplication of the gene for a muscle ion channel protein led to an electric organ Gene a (mutation 1) a (mutation 2) Electric organ none Figure 27.35

151 Stimulus and Response: Putting It All TogetherAn animal’s nervous system connects sensations derived from environmental stimuli to responses carried out by its muscles. Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

152 Figure 27.36 The nervous, sensory, and motor systems in action

153 Evolution Connection: Seeing UVMany birds can see ultraviolet light, which seems to be important in Social communication Food gathering Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences. © 2010 Pearson Education, Inc.

154 Researchers have discovered that a single amino acid change in the pigment protein rhodopsin converted it to a UV-detecting form. This is another example of a large scale change that can be traced to a small change: a single mutation. Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored. 2. Muscle cells are only capable of contracting. Therefore, students might wonder how muscles are relengthened. Opposing muscles or other physical forces (such as gravity) reverse actions and relengthen contracted muscles. 3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that allows our bones to accommodate the effects of mass and motion. Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems. 2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design. The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied. 3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints. 4. The nutritious elements inside of bone may not be consumed by a casual human diner. But in times of limited nutrition, boiling bones and/or breaking them open allows access to these additional nutrients. 5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass. 6. Students may need help to understand how the contraction of sarcomeres by microscopic distances adds up to large motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten each car by 1 foot, how much shorter will the train be? (100 feet) The collective contraction of sarcomeres adds up to much larger movements. 7. One way to help explain motor units is to make an analogy to the controls for sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just like in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit). 8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus. 9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff. Artificial selection has resulted in variations on these basic differences.

155 Figure 27.37 A European kestrel: a bird with UV vision

156 INTEGRATION Figure 27.UN01 Integration Orientation Figure Figure 27.UN01

157 SENSORY INPUT Figure 27.UN02Figure 27.UN02 Sensory Input Orientation Figure Figure 27.UN02

158 Figure 27.UN03 Motor Output Orientation Figure

159 Peripheral nervous system (PNS) Central nervous system (CNS)Sensory receptor SENSORY INPUT INTEGRATION Effector MOTOR OUTPUT Figure 27.UN04 Summary: Organization of Nervous Systems Peripheral nervous system (PNS) Central nervous system (CNS) Figure 27.UN04

160 Incoming signal Action poten tial signal Dendrites Cell body MyelinFigure 27.UN05 Summary: Neurons Dendrites Cell body Axon Myelin (speeds signal transmission) Synaptic terminal Figure 27.UN05

161 Central Nervous System Peripheral Nervous System(CNS) Peripheral Nervous System (PNS) Brain Spinal cord: nerve bundle that communicates with body Somatic nervous system: voluntary control over muscles Autonomic nervous system: involuntary control over organs Parasympathetic division: rest and digest  Figure 27.UN06 Summary: Central Nervous System and Peripheral Nervous System Sympathetic division: fight or flight  Figure 27.UN06

162       BRAIN Midbrain Hindbrain Forebrain (sophisticatedintegration) Midbrain Hindbrain Pons  Brainstem (filters motor and sensory input) Medulla oblongata  Thalamus  Cerebellum (coordinates movement)  Hypothalamus  Figure 27.UN07 Summary: The Human Brain Cerebrum  Figure 27.UN07

163 Sensory receptor cell Sensory neuron Action potential CNSStimulus CNS Figure 27.UN08 Summary: Sensory Transduction Figure 27.UN08

164 Organ of Corti (inside cochlea)Outer ear Middle ear Inner ear Figure 27.UN09 Summary: Hearing Eardrum Bones Organ of Corti (inside cochlea) Figure 27.UN09