1 The Nervous System : communicationA. Neurons = masses of nerve cells that transmit information 1. Cell Body - contains the nucleus and two extensions 2. Dendrites – shorter, more numerous, receive information 3. Axons - send information
2 Central Nervous System (CNS): brain and spinal cord.Peripheral Nervous System (PNS): nerves of the body -- Includes 31 pairs of spinal nerves -- And 12 pairs of cranial nerves
3 Basic Divisions of the Nervous SystemFigure 12.2
4 THREE BASIC FUNCTIONS OF THE NERVOUS SYSTEMSensory - gathers info Integrative - information is brought together Motor - responds to signals, homeostasis
5 Motor Functions Somatic Nervous System - skeletal (voluntary)Autonomic Nervous System - smooth muscles, glands (involuntary)
6 Neurons = nerve cells 1. Dendrites - receive information 2. Axons - conducts impulses
7 Neuroglial Cells (p 208) - support cells for the neurons
8 Neuroglial Cells (p 208) 1. Microglial Cells: digest debris or bacteria Microglial cells respond to immunological alarms
9 Neuroglial Cells (p 208) 2. Oligodendrocytes:makes the myelin sheath that provides insulation around the axons
10 3. Astrocytes: connect blood vessels to neuronsNeuroglial Cells (p 208) 3. Astrocytes: connect blood vessels to neurons I connect to blood vessels
11 4. Ependymal Cells: forms a membraneNeuroglial Cells (p 208) 4. Ependymal Cells: forms a membrane
12 5. Schwann cells: form the insulating myelin sheath around the neurons
13 Practice with neuroglia coloring!MYELIN SHEATHS - these serve as insulation around the axon Schwann cells supply the myelin for peripheral neurons. Oligodendrocytes myelinate the axons of the central nervous system. Practice with neuroglia coloring!
14 Supporting Cells - NEUROGLIA
15 Supporting Cells- NEUROGLIA
16 9.4 Neurons Axon - long section, transmits impulsesDendrite - extend from the cell body; receive information Neurofibrils - fibers within the axon
17 Chromatophilic substance (rough ER) - transport system Myelin -insulation surrounding axons Nodes of Ranvier - gaps in the insulation chromatophilic substance
18 Dendrites Nucleus Node of Ranvier Axon Myelin SheathChromatophilic substance Nucleus Node of Ranvier Axon Myelin Sheath
19 White vs Grey Matter Myelinated (white matter) – myelinated axons Unmyelinated (grey matter) - unmyelinated
20 Classification of NeuronsFunctional: Sensory - receives information from senses Motor - send information to muscles, organs, glands Interneurons - relay information
21 Structural: (A) Bipolar (B) Unipolar (C) Multipolar
22 Interesting Facts about the NeuronLongevity – can live and function for a lifetime Do not divide – fetal neurons lose their ability to undergo mitosis; neural stem cells are an exception High metabolic rate – require abundant oxygen and glucose The nerve fibers of newborns are unmyelinated - this causes their responses to stimuli to be coarse and sometimes involve the whole body. Try surprising a baby!
23 9.5 Cell Membrane PotentialResting Potential / Threshold Potential / Action Potential Nerve Impulse = weak electric current.
24 1. Neuron membrane maintains resting potential2. Threshold stimulus is received 3. Sodium channels open 4. Sodium ions diffuse inward, depolarizing the membrane 5. Potassium channels open 6. Potassium ions diffuse outward, repolarizing the membrane 7. The resulting action potential causes a local bioelectric current that stimulates adjacent* portions of the membrane. 8. Wave of action potentials travel the length of the axon as a nerve impulse * What does the word “adjacent” mean?
25 Ions in the cell and outside the cell create a positive and negative side, which produces an electric current.
26 9.6 Nerve Impulse Speed of an impulse is proportionate to the DIAMETER of the AXON. Greater diameter = faster speed **Myelinated Axons conduct faster than unmyelinated ones**
27 9.7 The Synapse A: Neuron (axon) B: Neuron (dendrite) MitochondriaVesicle Receptor Synapse Calcium Channel Releases neurotransmitter Re-uptake
28 Synapse - junction between two communicating neuronsNerve pathway - nerve impulse travels from neuron to neuron Dendrite → cell body → along axon -> synapse (gap) → dendrite
29 To complete the signal, a NEUROTRANSMITTER is released at the gap to signal the next neuron.Receptors on the dendrite receive the chemical message
30 Neurotransmitters Excitatory - increase membrane permeability, increases chance for threshold to be achieved Inhibitory - decrease membrane permeability, decrease chance for threshold to be achieved
31 Types of NeurotransmittersAcetylcholine - stimulates muscle contraction Monoamines - Norepinephrine & Dopamine (sense of feeling good, low levels = depression) Serotonin (sleepiness) and mood
32 Endorphins = reduction of pain, good moodCan be produced from exercise. The name “endorphin” comes from endo- and -orphin; intended to mean "a morphine-like substance originating from within the body.
33 The Science of Depression
34 Drugs that Affect Synapses and NeurotransmittersCurare - poison made from frog skin and causes paralysis by blocking Ach receptors at the neuromuscular junction.
35 Drugs that Affect Synapses and NeurotransmittersStrychnine poisoning can be fatal to humans and animals and can occur by inhalation, swallowing or absorption through eyes or mouth prevents the proper operation of the chemical that controls nerve signals to the muscles. The chemical controlling nerve signals works like the body's “off switch” for muscles. When this “off switch” does not work correctly, muscles throughout the body have severe, painful spasms. Read about Strychnine Poisoning
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37 In the normal communication process, dopamine is released by a neuron into the synapse, where it can bind to dopamine receptors on neighboring neurons. Normally, dopamine is then recycled back into the transmitting neuron by a specialized protein called the dopamine transporter. If cocaine is present, it attaches to the dopamine transporter and blocks the normal recycling process, resulting in a buildup of dopamine in the synapse, which contributes to the pleasurable effects of cocaine.
38 LSD; lysergic acid diethylamideActions/Effects: LSD alters the action of the neurotransmitters serotonin, norepinephrine, and dopamine, triggering extreme changes in brain function.
39 Dangers of Ecstasy (MDMA)The most common cause of Ecstasy-related death is overheating (hyperthermia). MDMA interferes with the body's ability to regulate its own body temperature and to see other warning signs allowing the body to overheat without discomfort especially when dancing for hours in hot clubs. The neurotransmitter serotonin is vital in regulating many of our basic functions. Serotonin is, among other things, the feel good neurotransmitter and helps to regulate body temp. Our brain cells are constantly trying to bring some amount of serotonin back into the cells and out of the synapse using serotonin reuptake transporters. Ecstasy essentially takes these upkeep transporters and reverses their roles. This causes a massive flood of serotonin from the brain cells into the synapse.
40 Antidepressants Zoloft is part of a class of drugs called selective serotonin reuptake inhibitors --SSRIs act on a specific chemical within the brain known as serotonin. -- seratonin is associated with mood and sleep
41 9.8 Impulse Processing Neuronal pool - groups of neurons that make hundreds of synaptic connections and work together to perform a common function These "pools" help us remember sequential tasks, like tying a shoe or riding a bike.
42 Sensory Nerves - conduct impulses into the brain or spinal cord 9.9 Types of Nerves Sensory Nerves - conduct impulses into the brain or spinal cord Motor Nerves - carry impulses to muscles or glands Mixed Nerves - contain both sensory and motor nerves
43 9.10 Nerve Pathways Reflex arc = simple path, only includes a few neurons ( involuntary, instantaneous) Knee-jerk reflex = maintains uprightedness Withdrawal reflex = avoidance of painful stimuli