1. 1 Hole’s Human Anatomy and Physiology Twelfth Edition Shier  Butler  Lewis Chapter 9 Muscular System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. 2 9.1: Introduction Three (3) Types of Muscle Tissues Skeletal Muscle Usually attached to bones Under conscious control Somatic nervous control Striated Smooth Muscle Walls of most viscera, blood vessels and skin Not under conscious control Autonomic Not striated Cardiac Muscle Wall of heart Not under conscious control Autonomic nervous control Striated

3. 3 9.2: Structure of Skeletal Muscle Skeletal Muscle Organ of the muscular system Skeletal muscle tissue Nervous tissue Blood Connective tissues Fascia Tendons Aponeuroses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aponeuroses Skeletal muscles Tendons

4. 4 Connective Tissue Coverings Muscle coverings: Epimysium Perimysium Endomysium Bone Muscle Epimysium Perimysium Endomysium Fascicle Fascicles Muscle fibers (cells) Myofibrils Thick and thin filaments Blood vessel Muscle fiber Myofibril Sarcolemma Nucleus Filaments Tendon Fascia (covering muscle) Axon of motor neuron Sarcoplasmic reticulum Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Muscle organ Fascicles Muscle cells or fibers Myofibrils Thick and thin myofilaments Actin and myosin proteins Titin is an elastic myofilament 5

5. 5 Skeletal Muscle Fibers Sarcolemma Sarcoplasm Sarcoplasmic reticulum (SR) Transverse (‘T’) tubule Triad Cisternae of SR T tubule Myofibril Actin myofilaments Myosin myofilaments Sarcomere Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleus Mitochondria Sarcolemma Sarcoplasm Nucleus Myofibrils Sarcoplasmic reticulum Openings into transverse tubules Thick and thin filaments Cisternae of sarcoplasmic reticulum Transverse tubule Triad

6. 6 9.3: Skeletal Muscle Contraction Movement within the myofilaments I band (thin) A band (thick and thin) H zone (thick) Z line (or disc) M line Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Myofibril Sarcomere (a) Skeletal muscle fiber Z lineH zoneM line I band (b) Z line Sarcoplasmic reticulum Thick (myosin) filaments Thin (actin) filaments A band

7. 7 Myofilaments Thick myofilaments Composed of myosin protein Form the cross-bridges Thin myofilaments Composed of actin protein Associated with troponin and tropomyosin proteins Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cross-bridges Actin molecule Thin filament Myosin molecule Thick filament Troponin Tropomyosin

8. 8 Neuromuscular Junction Also known as NMJ or myoneural junction Site where an axon and muscle fiber meet Parts to know: Motor neuron Motor end plate Synapse Synaptic cleft Synaptic vesicles Neurotransmitters Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Axon branches Mitochondria Acetylcholine (a) Synaptic vesicles Synaptic cleft Folded sarcolemma Motor end plate Myofibril of muscle fiber Muscle fiber nucleus Motor neuron axon 9

9. 9 Animation: Function of the Neuromuscular Junction Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

10. 10 Motor Unit Single motor neuron All muscle fibers controlled by motor neuron As few as four fibers As many as 1000’s of muscle fibers Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Motor neuron of motor unit 2 Motor neuron of motor unit 1 Skeletal muscle fibers Branches of motor neuron axon

11. 11 Stimulus for Contraction Acetylcholine (ACh) Nerve impulse causes release of ACh from synaptic vesicles ACh binds to ACh receptors on motor end plate Generates a muscle impulse Muscle impulse eventually reaches the SR and the cisternae Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Axon branches Mitochondria Acetylcholine (a) Synaptic vesicles Synaptic cleft Folded sarcolemma Motor end plate Myofibril of muscle fiber Muscle fiber nucleus Motor neuron axon 11

12. 12 Excitation-Contraction Coupling Muscle impulses cause SR to release calcium ions into cytosol Calcium binds to troponin to change its shape The position of tropomyosin is altered Binding sites on actin are now exposed Actin and myosin molecules bind via myosin cross-bridges Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Actin monomers Release of Ca +2 from sarcoplasmic reticulum exposes binding sites on actin: Muscle contraction Muscle relaxation Active transport of Ca +2 into sarcoplasmic reticulum, which requires ATP, makes myosin binding sites unavailable. Ca +2 binds to troponin Tropomyosin pulled aside ATP Contraction cycle PADP + P P Ca +2 PADP + P P P ADP P ATP PADP + P ATP Tropomyosin Troponin Thin filament Thick filament Ca +2 Binding sites on actin exposed 1Relaxed muscle Ca +2 PADP + Ca +2 2Exposed binding sites on actin molecules allow the muscle contraction cycle to occur 6ATP splits, which provides power to “cock” the myosin cross-bridges 3Cross-bridges bind actin to myosin 5New ATP binds to myosin, releasing linkages 4 Cross-bridges pull thin filament (power stroke), ADP and P released from myosin 13

13. Cross Bridge Cycling Myosin cross-bridge attaches to actin binding site Myosin cross-bridge pulls thin filament ADP and phosphate released from myosin New ATP binds to myosin Linkage between actin and myosin cross-bridge break ATP splits Myosin cross-bridge goes back to original position Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Actin monomers Release of Ca +2 from sarcoplasmic reticulum exposes binding sites on actin: Muscle contraction Muscle relaxation Active transport of Ca +2 into sarcoplasmic reticulum, which requires ATP, makes myosin binding sites unavailable. Ca +2 binds to troponin Tropomyosin pulled aside ATP Contraction cycle PADP + P P Ca +2 PADP + P P P ADP P ATP PADP + P ATP Tropomyosin Troponin Thin filament Thick filament Ca +2 Binding sites on actin exposed 1Relaxed muscle Ca +2 PADP + Ca +2 2Exposed binding sites on actin molecules allow the muscle contraction cycle to occur 6ATP splits, which provides power to “cock” the myosin cross-bridges 3Cross-bridges bind actin to myosin 5New ATP binds to myosin, releasing linkages 4 Cross-bridges pull thin filament (power stroke), ADP and P released from myosin

14. 14 The Sliding Filament Model of Muscle Contraction When sarcromeres shorten, thick and thin filaments slide past one another H zones and I bands narrow Z lines move closer together Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Z line (a) Z line Sarcomere Contracting Fully contracted Relaxed 2 3 1 A band Thin filaments Thick filaments

15. 15 Animation: The Cross-Bridge Cycle Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

16. 16 Animation: Breakdown of ATP and Cross-Bridge Movement Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

17. 17 Relaxation Acetylcholinesterase – rapidly decomposes Ach remaining in the synapse Muscle impulse stops Stimulus to sarcolemma and muscle fiber membrane ceases Calcium moves back into sarcoplasmic reticulum (SR) Myosin and actin binding prevented Muscle fiber relaxes

18. 18 Animation: Action Potentials and Muscle Contraction Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

19. 19 Energy Sources for Contraction Creatine phosphate – stores energy that quickly converts ADP to ATP 1) Creatine phosphate and 2) Cellular respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ADP ATP P When cellular Creatine ADP ATP P is high Creatine When cellular is low 17

20. 20 Animation: Energy Sources for Prolonged Exercise Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

21. 21 Oxygen Supply and Cellular Respiration Cellular respiration: Anaerobic Phase Glycolysis Occurs in cytoplasm Produces little ATP Aerobic Phase Citric acid cycle Electron transport system Occurs in the mitochondria Produces most ATP Myoglobin stores extra oxygen Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ATP2 Energy Lactic acid Glucose ATPSynthesis of 34 CO 2 + H 2 O + Energy Pyruvic acid Heat 2 1 Mitochondria Cytosol In the absence of sufficient oxygen, glycolysis leads to lactic acid accumulation. Oxygen carried from the lungs by hemoglobin in red blood cells is stored in muscle cells by myoglobin and is available to support aerobic respiration. Citric acid cycle Electron transport chain

22. 22 Oxygen Debt Oxygen not available Glycolysis continues Pyruvic acid converted to lactic acid Liver converts lactic acid to glucose Oxygen debt – amount of oxygen needed by liver cells to use the accumulated lactic acid to produce glucose Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ATP Glucose Glycogen Lactic acid Pyruvic acid Energy to synthesize Energy from Glycolysis and lactic acid formation (in muscle) Synthesis of glucose from lactic acid (in liver) ATP

23. 23 Muscle Fatigue Inability to contract muscle Commonly caused from: Decreased blood flow Ion imbalances across the sarcolemma Accumulation of lactic acid Cramp – sustained, involuntary muscle contraction

24. 24 Heat Production By-product of cellular respiration Muscle cells are major source of body heat Blood transports heat throughout body core

25. 25 9.4: Muscular Responses Muscle contraction can be observed by removing a single skeletal muscle fiber and connecting it to a device that senses and records changes in the overall length of the muscle fiber. Threshold Stimulus Minimal strength required to cause contraction

26. 26 Recording of a Muscle Contraction Recording a Muscle Contraction Twitch Latent period Period of contraction Period of relaxation Refractory period All-or-none response Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Force of contraction Time Latent period Period of contraction Period of relaxation Time of stimulation

27. 27 Length-Tension Relationship Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (b) Overly shortened(c) Overly stretched (a) Optimal length Muscle fiber length Force

28. 28 Summation Process by which individual twitches combine Produces sustained contractions Can lead to tetanic contractions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Time (c) (b) Force of contraction (a) Force of contraction Force of contraction

29. 29 Recruitment of Motor Units Recruitment - increase in the number of motor units activated Whole muscle composed of many motor units More precise movements are produced with fewer muscle fibers within a motor unit As intensity of stimulation increases, recruitment of motor units continues until all motor units are activated

30. 30 Sustained Contractions Smaller motor units (smaller diameter axons) - recruited first Larger motor units (larger diameter axons) - recruited later Produce smooth movements Muscle tone – continuous state of partial contraction

31. 31 Types of Contractions Isotonic – muscle contracts and changes length Concentric – shortening contraction Eccentric – lengthening contraction Isometric – muscle contracts but does not change length Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Movement (a) Muscle contracts with force greater than resistance and shortens (concentric contraction) (c) Muscle contracts but does not change length (isometric contraction) (b) Muscle contracts with force less than resistance and lengthens (eccentric contraction) No movement 29

32. 32 Fast Twitch and Slow Twitch Muscle Fibers Slow-twitch fibers (Type I) Always oxidative Resistant to fatigue Red fibers Most myoglobin Good blood supply Fast-twitch glycolytic fibers (Type IIa) White fibers (less myoglobin) Poorer blood supply Susceptible to fatigue Fast-twitch fatigue-resistant fibers (Type IIb) Intermediate fibers Oxidative Intermediate amount of myoglobin Pink to red in color Resistant to fatigue

33. 33 9.5: Smooth Muscles Compared to skeletal muscle fibers, smooth muscle fibers are: Shorter Single, centrally located nucleus Elongated with tapering ends Myofilaments randomly organized Lack striations Lack transverse tubules Sarcoplasmic reticula (SR) not well developed

34. 34 Smooth Muscle Fibers Visceral Smooth Muscle Single-unit smooth muscle Sheets of muscle fibers Fibers held together by gap junctions Exhibit rhythmicity Exhibit peristalsis Walls of most hollow organs Multi-unit Smooth Muscle Less organized Function as separate units Fibers function separately Iris of eye Walls of blood vessels

35. 35 Smooth Muscle Contraction Resembles skeletal muscle contraction in that: Interaction between actin and myosin Both use calcium and ATP Both are triggered by membrane impulses Different from skeletal muscle contraction in that: Smooth muscle lacks troponin Smooth muscle uses calmodulin Two neurotransmitters affect smooth muscle Acetlycholine (Ach) and norepinephrine (NE) Hormones affect smooth muscle Stretching can trigger smooth muscle contraction Smooth muscle slower to contract and relax Smooth muscle more resistant to fatigue Smooth muscle can change length without changing tautness

36. 36 9.6: Cardiac Muscle Located only in the heart Muscle fibers joined together by intercalated discs Fibers branch Network of fibers contracts as a unit Self-exciting and rhythmic Longer refractory period than skeletal muscle

37. 37 Characteristics of Muscle Tissue

38. 38 9.7: Skeletal Muscle Actions Skeletal muscles generate a great variety of body movements. The action of each muscle mostly depends upon the kind of joint it is associated with and the way the muscle is attached on either side of that joint.

39. 39 Origin and Insertion Origin – immovable end Insertion – movable end Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Radius Coracoid process Origins of biceps brachii Tendon of long head Tendon of short head Biceps brachii Insertion of biceps brachii

40. 40 Interaction of Skeletal Muscles Prime mover (agonist) – primarily responsible for movement Synergists – assist prime mover Antagonist – resist prime mover’s action and cause movement in the opposite direction of the prime mover

41. 41 9.9: Lifespan Changes Myoglobin, ATP, and creatine phosphate decline By age 80, half of muscle mass has atrophied Adipose cells and connective tissues replace muscle tissue Exercise helps to maintain muscle mass and function

42. 42 Muscles of Facial Expression

43. 43 Muscles of Mastication

44. 44 Muscles That Move the Head and Vertebral Column

45. 45 Muscles That Move the Pectoral Girdle

46. 46 Muscles That Move the Arm

47. 47 Muscles That Move the Forearm

48. 48 Muscles That Move the Hand Flexors (anterior) and extensors (posterior)

49. 49 Muscles of the Abdominal Wall

50. 50 Muscles of the Pelvic Outlet

51. 51 Muscles That Move the Thigh

52. 52 Muscles That Move the Leg

53. 53 Muscles That Move the Foot

54. 54 Important Points in Chapter 9: Outcomes to be Assessed 9.1: Introduction List various outcomes of muscle action. 9.2: Structure of a Skeletal Muscle Describe how connective tissue is a part of the structure of a skeletal muscle. Name the major parts of a skeletal muscle fiber and describe the functions of each. 9.3: Skeletal Muscle Contraction Describe the neural control of skeletal muscle contraction. Identify the major events that occur during skeletal muscle fiber contraction.

55. 55 Important Points in Chapter 9: Outcomes to be Assessed List the energy sources for skeletal muscle fiber contraction. Describe how a muscle may become fatigued. Describe oxygen debt. 9.4: Muscular Responses Distinguish between fast and slow twitch muscle fibers. Distinguish between a twitch and a sustained contraction. Describe how exercise affects skeletal muscles. Explain how various types of muscular contractions produce body movements and help maintain posture.

56. 56 Important Points in Chapter 9: Outcomes to be Assessed 9.5: Smooth Muscle Distinguish between the structures and functions of multiunit smooth muscle and visceral smooth muscle. Compare the contraction mechanisms of skeletal and smooth muscle fibers. 9.6: Cardiac Muscle Compare the contraction mechanisms of skeletal and cardiac muscle fibers. 9.7: Skeletal Muscle Actions Explain how the attachments, locations, and interactions of skeletal muscles make possible certain movements.

57. 57 Important Points in Chapter 9: Outcomes to be Assessed 9.8: Major Skeletal Muscles Identify and locate the skeletal muscles of each body region and describe the action (s) of each muscle.