1 Chapter 08 *Lecture Outline*See separate Image PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. PowerPoints prepared by Melanie Waite-Altringer Biology Faculty Member of Anoka-Ramsey Community College Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 Chapter 8 Muscular System

3 Introduction: A. All movements require muscle which are organs using chemical energy to contract. B. The three types of muscle in the body are skeletal, smooth, and cardiac muscle. C. This chapter focuses on skeletal muscle.

4 Structure of a Skeletal MuscleA. Each muscle is an organ, comprised of skeletal muscle tissue, nervous tissue, blood, and other connective tissues B. Connective Tissue Coverings 1. Layers of dense connective tissue, called fascia, surround and separate each muscle. 2. This connective tissue extends beyond the ends of the muscle and gives rise to tendons that are fused to the periosteum of bones.

5 3. Sometimes muscles are. connected to each other by broad3. Sometimes muscles are connected to each other by broad sheets of connective tissue called aponeuroses. 4. The layer of connective tissue around each whole muscle is the epimysium; the perimysium surrounds individual bundles (fascicles) within each muscle; and each muscle cell (fiber) is covered by a connective tissue layer called endomysium.

6 Fig08.01 Muscle Bone Fascicles Tendon Muscle fibers (cells) FasciaCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Muscle Bone Fascicles Tendon Muscle fibers (cells) Fascia (covering muscle) Myofibrils Epimysium Perimysium Thick and thin filaments Endomysium Fascicle Axon of motor neuron Blood vessel Nucleus Sarcoplasmic reticulum Myofibril Filaments Muscle fiber Sarcolemma

7 C. Skeletal Muscle Fibers1. Each muscle fiber is a single, long, cylindrical muscle cell. 2. Beneath the sarcolemma (cell membrane) lies sarcoplasm (cytoplasm) with many mitochondria and nuclei; the sarcoplasm contains myofibrils.

8 a. Thick filaments of myofibrils are made up of the protein myosin.b. Thin filaments of myofibrils are made up of the protein actin. c. The organization of these filaments produces striations.

9 3. A sarcomere extends from one Z line to the next.a. I bands (light bands) made up of actin filaments are anchored to Z lines. b. A bands (dark bands) are made up of overlapping thick and thin filaments. c. In the center of A bands is an H zone, consisting of myosin filaments only.

10 Fig08.02 Skeletal muscle fiber Sarcoplasmic reticulum Myosin (thick)Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Skeletal muscle fiber Sarcoplasmic reticulum Myosin (thick) filaments Actin (thin) filaments Myofibril Sarcomere H zone Z line Z line M line I band A band I band A band (a) (b)

11 4. Beneath the sarcolemma of a muscle4. Beneath the sarcolemma of a muscle fiber lies the sarcoplasmic reticulum (endoplasmic reticulum), which is associated with transverse (T) tubules (invaginations of the sarcolemma). a. Each T tubule lies between two cisternae of the sarcoplasmic reticulum and is open to the outside of the muscle fiber. b. The sarcoplasmic reticulum and transverse tubules activate the muscle contraction mechanism when the fiber is stimulated.

12 sarcoplasmic reticulumFig08.04 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Myofibrils Cisternae of sarcoplasmic reticulum Nucleus Transverse tubule Sarcoplasmic reticulum Openings into transverse tubules Mitochondria Nucleus Thick and thin filaments Sarcolemma Sarcoplasm

13 D. Neuromuscular Junction1. The site where the motor neuron and muscle fiber meet is the neuromuscular junction. a. The muscle fiber membrane forms a motor end plate in which the sarcolemma is tightly folded and where nuclei and mitochondria are abundant. b. The cytoplasm of the motor neuron contains numerous mitochondria and synaptic vesicles storing neurotransmitters. Its functional connection is called a synapse.

14 Synaptic vesicles Mitochondria Motor neuron axon AcetylcholineFig08.05 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Synaptic vesicles Mitochondria Motor neuron axon Acetylcholine Synaptic cleft Folded sarcolemma Motor end plate Muscle fiber nucleus Myofibril of muscle fiber

15 Skeletal Muscle ContractionA. Muscle contraction involves several components that result in the shortening of sarcomeres, and the pulling of the muscle against its attachments.

16 B. Role of Myosin and ActinMyosin consists of two twisted strands with globular cross-bridges projected outward along the strands. Actin is a globular protein with myosin binding sites; tropomysosin and troponin are two proteins associated with the surface of the actin filaments.

17 Cross-bridges Actin filament Troponin Tropomyosin Myosin moleculeFig08.06 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Cross-bridges Actin filament Troponin Tropomyosin Myosin molecule Myosin filament Actin molecule

18 3. According to the sliding filament. model of muscle contraction, the3. According to the sliding filament model of muscle contraction, the myosin crossbridge attaches to the binding site on the actin filament and bends, pulling on the actin filament; it then releases and attaches to the next binding site on the actin, pulling again. 4. Energy from the conversion of ATP to ADP is provided to the cross- bridges from the enzyme ATPase, causing them to be in a “cocked” position.

19 C. Stimulus for Contraction1. The motor neuron must release the neurotransmitter acetylcholine from its synaptic vesicles into the synaptic cleft in order to initiate a muscle contraction. 2. Protein receptors in the motor end plate detect the neurotransmitters, and a muscle impulse spreads over the surface of the sarcolemma and into the T tubules, where it reaches the sarcoplasmic reticulum.

20 3. Upon receipt of the muscle impulse,3. Upon receipt of the muscle impulse, the sarcoplasmic reticulum releases its stored calcium to the sarcoplasm of the muscle fiber. 4. The high concentration of calcium in the sarcoplasm interacts with the troponin and tropomyosin molecules, which move aside, exposing the myosin binding sites on the actin filaments.

21 5. Myosin cross-bridges now bind and5. Myosin cross-bridges now bind and pull on the actin filaments, causing the sarcomeres to shorten. 6. After the nervous impulse has been received, acetylcholinesterase rapidly decomposes the acetylcholine. 7. Then, calcium is returned to the sarcoplasmic reticulum, and the linkages between myosin and actin are broken.

22 Fig08.07 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Tropomyosin Troponin Actin lament Actin molecules ADP + P ADP + P Myosin lament 1 Relaxed muscle Ca+2 Ca+2 Muscle contraction Muscle relaxation Release of Ca+2 from sarcoplasmic reticulum exposes binding sites on thin lament: Active transport of Ca+2 into sarcoplasmic reticulum, which requires ATP, makes myosin binding sites unavailable. Ca+2 binds to troponin ATP Tropomyosin pulled aside Binding sites on actin lament exposed Ca+2 Ca+2 Ca+2 ADP + P ADP + P 2 Exposed binding sites on actin allow the muscle contraction cycle to occur ADP + P ADP + P Contraction cycle ADP + P ADP + P 6 ATP splits, which provides power to “Cock” the myosin cross-bridge 3 Cross-bridge binds actin to myosin ADP ADP ATP ATP ATP P P ATP ADP + P 5 New ATP binds to myosin, causing linkage to release 4 Cross-bridge pulls actin lament (power stroke), ADP and released from myosin P

23 Fig08.08 Sarcomere Sarcomere A band A band Z line Z line Z line Z lineCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Sarcomere Sarcomere A band A band Z line Z line Z line Z line 1 Relaxed Thin filaments Thick filaments 2 Contracting (b) ©Muscular Dystrophy Association (a) 3 Fully contracted ©Gianni Giansanti/Corbis

24 D. Energy Sources for Contraction Energy for contraction comes from molecules of ATP. This chemical is in limited supply and so must often be regenerated 2. Creatine phosphate, which stores excess energy released by the mitochondria, is present to regenerate ATP from ADP and phosphate.

25 3. Whenever the supply of ATP is. sufficient, creatine phosphokinase3. Whenever the supply of ATP is sufficient, creatine phosphokinase promotes the synthesis of creatine phosphate. 4. As ATP decomposes, the energy from creatine phosphate can be transferred to ADP molecules, converting them back to ATP.

26 E. Oxygen Supply and Cellular Respiration1. The early phase of cellular respiration yields few molecules of ATP, so muscle has a high requirement for oxygen, which enables the complete breakdown of glucose in the mitochondria. 2. Hemoglobin in red blood cells carries oxygen to muscle. 3. The pigment myoglobin stores oxygen in muscle tissue.

27 F. Oxygen Debt 1. During rest or moderate activity, there is enough oxygen to support aerobic respiration. 2. Oxygen deficiency may develop during strenuous exercise, and pyruvic acid forms then reacts to form lactic acid accumulates as an end product of anaerobic respiration. a. Lactic acid diffuses out of muscle cells and is carried in the bloodstream to the liver.

28 3. Oxygen debt refers to the amount of3. Oxygen debt refers to the amount of oxygen that liver cells require to convert the accumulated lactic acid into glucose, plus the amount that muscle cells need to resynthesize ATP and creatine phosphate to their original concentrations. 4. Repaying an oxygen debt may take several hours.

29 G. Muscle Fatigue 1. When a muscle loses its ability to contract during strenuous exercise, it is referred to as fatigue. 2. Muscle fatigue usually arises from the accumulation of lactic acid in the muscle. a. A lowered pH as a result of accumulated lactic acid prevents the muscle from contracting. 3. A muscle cramp occurs due to a lack of ATP required to return calcium ions back to the sarcoplasmic reticulum so muscle fibers can relax.

30 H. Heat Production 1. Contraction of skeletal muscle represents an important source of heat for the body. 2. Much of the energy produced through the reactions of cellular respiration is lost as heat (another source of heat for the body).

31 Muscular Responses A. One method of studying muscle function is to remove a single fiber and connect it to a device that records its responses to electrical stimulation. B. Threshold Stimulus 1. A muscle fiber remains unresponsive to stimulation unless the stimulus is of a certain strength, called the threshold stimulus.

32 C. Recording a Muscular Contraction1. A single, short contraction involving only a few motor units is referred to as a twitch. 2. A myogram is the recording of an electrically-stimulated muscle contraction. 3. A latent period is a brief delay between the stimulation and beginning of the contraction

33 Force of contraction Latent period Period of contraction Period ofFig08.11 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Force of contraction Latent period Period of contraction Period of relaxation Time of stimulation Time

34 4. When a muscle fiber contracts, it4. When a muscle fiber contracts, it contracts to its full extent (all-or- none response). 5. The latent period is followed by a period of contraction and a period of relaxation.

35 E. Summation 1. A muscle fiber receiving a series of stimuli of increasing frequency reaches a point when it is unable to relax completely and the force of individual twitches combine by the process of summation. 2. If the sustained contraction lacks any relaxation, it is called a tetanic contraction.

36 Fig08.12 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display (a) (b) (c) Time

37 F. Recruitment of Motor Units1. A motor neuron and the muscle fibers it controls make up a motor unit; when stimulated to do so, the muscle fibers of the motor unit contract all at once. 2. An increase in the number of activated motor units within a muscle at higher intensities of stimulation is called recruitment.

38 G. Sustained Contractions1. Summation and recruitment together can produce a sustained contraction of increasing strength. 2. Muscle tone is achieved by a continuous state of sustained contraction of motor units within a muscle.

39 A. Smooth Muscle Fibers Smooth Muscles1. Smooth muscle cells are elongated with tapered ends, lack striations and have a relatively undeveloped sarcoplasmic reticulum.

40 2. Multiunit smooth muscle and visceral muscle are two types of smooth muscles.a. In multiunit smooth muscle, such as in the blood vessels and iris of the eye, fibers occur separately rather than as sheets.

41 b. Visceral smooth muscle. occurs in sheets and is foundb. Visceral smooth muscle occurs in sheets and is found in the walls of hollow organs; these fibers can stimulate one another and display rhythmicity, and are thus responsible for peristalsis in hollow organs and tubes.

42 B. Smooth Muscle Contraction1. The myosin-binding-to-actin mechanism is mostly the same for smooth muscles and skeletal muscles. 2. Both acetylcholine and norepinephrine stimulate and inhibit smooth muscle contraction, depending on the target muscle.

43 3. Hormones can also stimulate or inhibit contraction.4. Smooth muscle is slower to contract and relax than is skeletal muscle, but can contract longer using the same amount of ATP.

44 Cardiac Muscle A. The mechanism of contraction in cardiac muscle is essentially the same as that for skeletal and smooth muscle, but with some differences. B. Cardiac muscle has transverse tubules that supply extra calcium, and can thus contract for longer periods.

45 C. Complex membrane junctions,. called intercalated discs, join cellsC. Complex membrane junctions, called intercalated discs, join cells and transmit the force of contraction from one cell to the next, as well as aid in the rapid transmission of impulses throughout the heart. D. Cardiac muscle is self-exciting and rhythmic, and the whole structure contracts as a unit.

46 Skeletal Muscle ActionsA. Origin and Insertion 1. The immovable end of a muscle is the origin, while the movable end is the insertion; contraction pulls the insertion toward the origin. 2. Some muscles have more than one insertion or origin.

47 Coracoid process Origins of biceps brachii Tendon of long headFig08.14 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Coracoid process Origins of biceps brachii Tendon of long head Tendon of short head Biceps brachii Radius Insertion of biceps brachii

48 B. Interaction of Skeletal Muscles1. Of a group of muscles, the one doing the majority of the work is the prime mover/agonist. 2. Helper muscles are called synergists; opposing muscles are called antagonists.

49 Major Skeletal MusclesA. Muscles are named according to any of these: size, shape, location, action, number of attachments, or direction of its fibers.

50 Fig08.15 Frontalis Orbicularis oculi Zygomaticus MasseterCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Frontalis Orbicularis oculi Zygomaticus Masseter Orbicularis oris Trapezius Sternocleido- mastoid Deltoid Pectoralis major Serratus anterior Biceps brachii Brachialis External oblique Brachioradialis Rectus abdominis T ensor fasciae latae Sartorius Rectus femoris Gracilis Adductor longus Vastus medialis Vastus lateralis Fibularis longus Gastrocnemius Tibialis anterior Soleus Extensor digitorum longus

51 Fig08.16 Temporalis Occipitalis Sternocleidomastoid Trapezius DeltoidCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Temporalis Occipitalis Sternocleidomastoid Trapezius Deltoid Teres minor Infraspinatus Teres major Brachialis Triceps brachii Rhomboid Latissimus dorsi External oblique Gluteus medius Gluteus maximus Adductor magnus Biceps femoris Gracilis Semitendinosus Semimembranosus Vastus lateralis Sartorius Gastrocnemius Fibularis longus Calcaneal tendon Soleus

52 B. Muscles of Facial Expression1. Muscles of facial expression attach to underlying bones and overlying connective tissue of skin, and are responsible for the variety of facial expressions possible in the human face. 2. Major muscles include the epicranius, orbicularis oculi orbicularis oris, buccinator, zygomaticus, and playtsma

53 Epicranial aponeurosis FrontalisFig08.17a Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Epicranial aponeurosis Frontalis Epicranius Occipitalis Temporalis Orbicularis oculi Zygomaticus Masseter Buccinator Sternocleidomastoid Orbicularis oris Platysma (a)

54 C. Muscles of Mastication1. Chewing movements include up and down as well as side-to-side grinding motions of muscles attached to the skull and lower jaw. 2. Chewing muscles include the masseter and temporalis.

55 D. Muscles that Move the Head1. Paired muscles in the neck and back flex, extend, and turn the head. 2.  Major muscles include the sternocleidomastoid, splenius capitis, and semispinalis capitis.

56 Splenius capitis (cut)Fig08.17b Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Splenius capitis (cut) Splenius capitis Semispinalis capitis (b)

57 E. Muscles that Move the Pectoral Girdle1. The chest and shoulder muscles move the scapula. 2. Major muscles include the trapezius, rhomboideus major, levator scapulae, serratus anterior, and pectoralis minor.

58 Fig08.18 Levator scapulae Trapezius Supraspinatus DeltoidCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Levator scapulae Trapezius Supraspinatus Deltoid Infraspinatus Teres minor Teres major Rhomboid major Latissimus dorsi

59 (band of connective tissue)Fig08.19 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Trapezius Sternocleidomastoid Pectoralis minor Deltoid Internal intercostal Pectoralis major External intercostal Serratus anterior Rectus abdominis Linea alba (band of connective tissue) Internal oblique External oblique Transversus abdominis Aponeurosis of external oblique

60 F. Muscles that Move the Arm1. Muscles connect the arm to the pectoral girdle, ribs, and vertebral column, making the arm freely movable. 2. Flexors include the coracobrachialis and pectoralis major.

61 3. Extensors include the teres majorand latissimus dorsi. 4. Abductors include the supraspinatus and the deltoid. 5. Rotators are the subscapularis, infraspinatus, and teres minor.

62 Levator scapulae Supraspinatus Spine of scapula Deltoid InfraspinatusFig08.20 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Levator scapulae Supraspinatus Spine of scapula Deltoid Infraspinatus Teres minor Teres major Long head of triceps brachii Lateral head of triceps brachii

63 Trapezius Clavicle Subscapularis Deltoid CoracobrachialisFig08.21 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Trapezius Clavicle Subscapularis Deltoid Coracobrachialis Medial border of scapula Short head of biceps brachii Long head of biceps brachii Brachialis

64 G. Muscles that Move the Forearm. 1. These muscles arise from theG. Muscles that Move the Forearm These muscles arise from the humerus or pectoral girdle and connect to the ulna and radius. 2. Flexors are the biceps brachii, brachialis, and brachioradialis. 3. An extensor is the triceps brachii muscle. 4. Rotators include the supinator, pronator teres, and pronator quadratus.

65 Fig08.22 Biceps brachii Brachialis Supinator Pronator teresCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Biceps brachii Brachialis Supinator Pronator teres Brachioradialis Extensor carpi radialis longus Flexor carpi radialis Palmaris longus Flexor carpi ulnaris Pronator quadratus

66 H. Muscles that Move the Hand1. Movements of the hand are caused by muscles originating from the distal humerus, and the radius and ulna. 2. Flexors include the flexor carpi radialis, flexor carpi ulnaris, palmaris longus, and flexor digitorum profundus. 3. Extensors include the extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, and extensor digitorum.

67 Fig08.23 Triceps brachii Brachioradialis Extensor carpiCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Triceps brachii Brachioradialis Extensor carpi radialis longus Flexor carpi ulnaris Extensor carpi radialis brevis Extensor carpi ulnaris Extensor digitorum

68 I. Muscles of the Abdominal Wall1. This group of muscles connects the rib cage and vertebral column to the pelvic girdle. a. A band of tough connective tissue, the linea alba, extending from the xiphoid process to the symphysis pubis, serves as an attachment for certain abdominal wall muscles.

69 2. These four muscles include the: external oblique, internal oblique, transverse abdominis, and rectus abdominis.

70 J. Muscles of the Pelvic Outlet1. The deeper pelvic diaphragm forms the floor of the pelvic cavity and the superficial urogenital fills the space within the pubic arch. 2. Pelvic diaphragm muscles include the levator ani. 3. Urogenital diaphragm includes the superficial transversus perinei, bulbospongiosus, and ischiocavernosus.

71 Fig08.24 Scrotum Penis Clitoris Ischiocavernosus Urethral orificeCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Scrotum Penis Clitoris Ischiocavernosus Urethral orifice Bulbospongiosus Vaginal orifice Superficial Transversus perinei Anus Anus Levator ani Gluteus maximus External anal sphincter (a) (b) Coccyx Coccygeus Levator ani Rectum Vagina Urethra Urogenital diaphragm Pubic symphysis (c)

72 K. Muscles that Move the Thigh1. The muscles that move the thigh are attached to the femur and to the pelvic girdle. 2. Anterior group muscles include the psoas major and iliacus.

73 Fig08.25 Psoas major Iliacus Tensor fasciae latae SartoriusCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Psoas major Iliacus Tensor fasciae latae Sartorius Adductor longus Rectus femoris Adductor magnus Vastus lateralis Gracilis Vastus medialis Patella Patellar ligament

74 3. Posterior group muscles include the3. Posterior group muscles include the gluteus maximus, gluteus medius, gluteus minimus, and tensor fasciae latae. 4. Thigh adductors include the adductor longus, adductor magnus, and gracilis.

75 L. Muscles that Move the Leg1. This group connects the tibia or fibula to the femur or pelvic girdle. 2. Flexors are the biceps femoris, semitendinosus, semimembranosus, and sartorius. 3. An extensor is the quadriceps femoris group composed of four parts: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius.

76 Fig08.26 Gluteus medius Tensor fasciae latae Gluteus maximus SartoriusCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Gluteus medius Tensor fasciae latae Gluteus maximus Sartorius Rectus femoris Vastus lateralis Biceps femoris Iliotibial tract (band)

77 Fig08.27 Gluteus medius Gluteus maximus Adductor magnusCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Gluteus medius Gluteus maximus Adductor magnus Vastus lateralis covered by fascia Gracilis Semitendinosus Biceps femoris Semimembranosus Sartorius Gastrocnemius

78 M. Muscles that Move the Foot.1. Muscles that move the foot are attached to the femur, fibula, or tibia, and move the foot upward, downward, or in a turning motion. 2. Dorsal flexors include the tibialis anterior, fibularis (peroneus) tertius, and extensor digitorum longus. 3. Plantar flexors are the gastrocnemius soleus, and flexor digitorum longus. 4. An invertor is the tibialis posterior. 5. An evertor is the fibularis (peroneus) longus.

79 Fig08.28 Patella Patellar ligament Gastrocnemius Tibialis anteriorCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Patella Patellar ligament Gastrocnemius Tibialis anterior Fibularis longus Extensor digitorum longus Soleus Tibia

80 Fig08.29 Biceps femoris Vastus lateralis Head of fibula GastrocnemiusCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Biceps femoris Vastus lateralis Head of fibula Gastrocnemius Soleus Tibialis anterior Fibularis longus Extensor digitorum longus Calcaneal tendon Fibularis tertius

81 Fig08.30 Semitendinosus Biceps femoris Semimembranosus GracilisCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Semitendinosus Biceps femoris Semimembranosus Gracilis Sartorius Gastrocnemius: Medial head Lateral head Fibularis longus Soleus Calcaneal tendon Flexor digitorum longus Calcaneus