1. Essentials of Human Anatomy & Physiology Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Seventh Edition Elaine N. Marieb Chapter 7 The Muscular System

3. The Muscular System Slide 6.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Muscles are responsible for all types of body movement – they contract or shorten and are the machine of the body  Three basic muscle types are found in the body  Skeletal muscle  Cardiac muscle  Smooth muscle

4. Characteristics of Muscles Slide 6.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Muscle cells are elongated (muscle cell = muscle fiber)  Contraction of muscles is due to the movement of microfilaments  All muscles share some terminology  Prefix myo refers to muscle  Prefix mys refers to muscle  Prefix sarco refers to flesh

5. Skeletal Muscle Characteristics Slide 6.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Most are attached by tendons to bones  Cells are multinucleate  Striated – have visible banding  Voluntary – subject to conscious control  Cells are surrounded and bundled by connective tissue = great force, but tires easily

6. Connective Tissue Wrappings of Skeletal Muscle Slide 6.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Endomysium – around single muscle fiber  Perimysium – around a fascicle (bundle) of fibers Figure 6.1

7. Connective Tissue Wrappings of Skeletal Muscle Slide 6.4b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Epimysium – covers the entire skeletal muscle  Fascia – on the outside of the epimysium Figure 6.1

8. Skeletal Muscle Attachments Slide 6.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Epimysium blends into a connective tissue attachment  Tendon – cord-like structure  Aponeuroses – sheet-like structure  Sites of muscle attachment  Bones  Cartilages  Connective tissue coverings

9. Smooth Muscle Characteristics Slide 6.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Has no striations  Spindle-shaped cells  Single nucleus  Involuntary – no conscious control  Found mainly in the walls of hollow organs  Slow, sustained and tireless Figure 6.2a

10. Cardiac Muscle Characteristics Slide 6.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Has striations  Usually has a single nucleus  Joined to another muscle cell at an intercalated disc  Involuntary  Found only in the heart  Steady pace! Figure 6.2b

11. Function of Muscles Slide 6.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Produce movement  Maintain posture  Stabilize joints  Generate heat

12. Microscopic Anatomy of Skeletal Muscle Slide 6.9a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Cells are multinucleate  Nuclei are just beneath the sarcolemma Figure 6.3a

13. Microscopic Anatomy of Skeletal Muscle Slide 6.9b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sarcolemma – specialized plasma membrane  Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum Figure 6.3a

14. Microscopic Anatomy of Skeletal Muscle Slide 6.10a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Myofibril  Bundles of myofilaments  Myofibrils are aligned to give distrinct bands  I band = light band  A band = dark band Figure 6.3b

15. Microscopic Anatomy of Skeletal Muscle Slide 6.10b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sarcomere  Contractile unit of a muscle fiber Figure 6.3b

16. Microscopic Anatomy of Skeletal Muscle Slide 6.11a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Organization of the sarcomere  Thick filaments = myosin filaments  Composed of the protein myosin  Has ATPase enzymes Figure 6.3c

17. Microscopic Anatomy of Skeletal Muscle Slide 6.11b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Organization of the sarcomere  Thin filaments = actin filaments  Composed of the protein actin Figure 6.3c

18. Microscopic Anatomy of Skeletal Muscle Slide 6.12a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Myosin filaments have heads (extensions, or cross bridges)  Myosin and actin overlap somewhat Figure 6.3d

19. Properties of Skeletal Muscle Activity (single cells or fibers) Slide 6.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Irritability – ability to receive and respond to a stimulus  Contractility – ability to shorten when an adequate stimulus is received

20. Nerve Stimulus to Muscles Slide 6.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Skeletal muscles must be stimulated by a nerve to contract (motor neruron)  Motor unit  One neuron  Muscle cells stimulated by that neuron Figure 6.4a

21. Nerve Stimulus to Muscles Slide 6.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neuromuscular junctions – association site of nerve and muscle Figure 6.5b

22. Nerve Stimulus to Muscles Slide 6.15b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Synaptic cleft – gap between nerve and muscle  Nerve and muscle do not make contact  Area between nerve and muscle is filled with interstitial fluid Figure 6.5b

23. Transmission of Nerve Impulse to Muscle Slide 6.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neurotransmitter – chemical released by nerve upon arrival of nerve impulse  The neurotransmitter for skeletal muscle is acetylcholine  Neurotransmitter attaches to receptors on the sarcolemma  Sarcolemma becomes permeable to sodium (Na + )

24. Transmission of Nerve Impulse to Muscle Slide 6.16b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sodium rushing into the cell generates an action potential  Once started, muscle contraction cannot be stopped

25. The Sliding Filament Theory of Muscle Contraction Slide 6.17a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Activation by nerve causes myosin heads (crossbridges) to attach to binding sites on the thin filament  Myosin heads then bind to the next site of the thin filament Figure 6.7

26. The Sliding Filament Theory of Muscle Contraction Slide 6.17b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  This continued action causes a sliding of the myosin along the actin  The result is that the muscle is shortened (contracted) Figure 6.7

27. The Sliding Filament Theory Slide 6.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.8

28. Contraction of a Skeletal Muscle Slide 6.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Muscle fiber contraction is “all or none”  Within a skeletal muscle, not all fibers may be stimulated during the same interval  Different combinations of muscle fiber contractions may give differing responses  Graded responses – different degrees of skeletal muscle shortening, rapid stimulus = constant contraction or tetanus

29. Muscle Response to Strong Stimuli Slide 6.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Muscle force depends upon the number of fibers stimulated  More fibers contracting results in greater muscle tension  Muscles can continue to contract unless they run out of energy

30. Energy for Muscle Contraction Slide 6.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Initially, muscles used stored ATP for energy  Bonds of ATP are broken to release energy  Only 4-6 seconds worth of ATP is stored by muscles  After this initial time, other pathways must be utilized to produce ATP

31. Energy for Muscle Contraction Slide 6.24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Direct phosphorylation  Muscle cells contain creatine phosphate (CP)  CP is a high-energy molecule  After ATP is depleted, ADP is left  CP transfers energy to ADP, to regenerate ATP  CP supplies are exhausted in about 20 seconds Figure 6.10a

32. Energy for Muscle Contraction Slide 6.26a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Anaerobic glycolysis  Reaction that breaks down glucose without oxygen  Glucose is broken down to pyruvic acid to produce some ATP  Pyruvic acid is converted to lactic acid Figure 6.10b

33. Energy for Muscle Contraction Slide 6.26b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Anaerobic glycolysis (continued)  This reaction is not as efficient, but is fast  Huge amounts of glucose are needed  Lactic acid produces muscle fatigue Figure 6.10b

34. Energy for Muscle Contraction Slide 6.25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Aerobic Respiration  Series of metabolic pathways that occur in the mitochondria  Glucose is broken down to carbon dioxide and water, releasing energy  This is a slower reaction that requires continuous oxygen Figure 6.10c

35. Muscle Fatigue and Oxygen Debt Slide 6.27 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  When a muscle is fatigued, it is unable to contract  The common reason for muscle fatigue is oxygen debt  Oxygen must be “repaid” to tissue to remove oxygen debt  Oxygen is required to get rid of accumulated lactic acid  Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less

36. Types of Muscle Contractions Slide 6.28 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Isotonic contractions  Myofilaments are able to slide past each other during contractions  The muscle shortens  Isometric contractions  Tension in the muscles increases  The muscle is unable to shorten

37. Muscle Tone Slide 6.29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Some fibers are contracted even in a relaxed muscle  Different fibers contract at different times to provide muscle tone  The process of stimulating various fibers is under involuntary control

38. Muscles and Body Movements Slide 6.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Movement is attained due to a muscle moving an attached bone Figure 6.12

39. Muscles and Body Movements Slide 6.30b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Muscles are attached to at least two points  Origin – attachment to a moveable bone  Insertion – attachment to an immovable bone Figure 6.12

40. Effects of Exercise on Muscle Slide 6.31 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Results of increased muscle use  Increase in muscle size  Increase in muscle strength  Increase in muscle efficiency  Muscle becomes more fatigue resistant

41. Types of Ordinary Body Movements Slide 6.32 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Flexion – decreases angle of joint and brings two bones closer together  Extension- opposite of flexion  Rotation- movement of a bone in longitudinal axis, shaking head “no”  Abduction/Adduction (see slides)  Circumduction (see slides)

42. Body Movements Slide 6.33 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.13

43. Left: Abduction – moving the leg away from the midline Above – Adduction- moving toward the midline Right: Circumduction: cone- shaped movement, proximal end doesn’t move, while distal end moves in a circle.

44. Types of Muscles Slide 6.35 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Prime mover – muscle with the major responsibility for a certain movement  Antagonist – muscle that opposes or reverses a prime mover  Synergist – muscle that aids a prime mover in a movement and helps prevent rotation

45. Naming of Skeletal Muscles Slide 6.36a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Direction of muscle fibers  Example: rectus (straight)  Relative size of the muscle  Example: maximus (largest)

46. Naming of Skeletal Muscles Slide 6.36b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Location of the muscle  Example: many muscles are named for bones (e.g., temporalis)  Number of origins  Example: triceps (three heads)

47. Naming of Skeletal Muscles Slide 6.37 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Location of the muscles origin and insertion  Example: sterno (on the sternum)  Shape of the muscle  Example: deltoid (triangular)  Action of the muscle  Example: flexor and extensor (flexes or extends a bone)

48. Head and Neck Muscles Slide 6.38 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.14

49. Trunk Muscles Slide 6.39 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.15

50. Deep Trunk and Arm Muscles Slide 6.40 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.16

51. Muscles of the Pelvis, Hip, and Thigh Slide 6.41 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.18c

52. Muscles of the Lower Leg Slide 6.42 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.19

53. Superficial Muscles: Anterior Slide 6.43 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.20

54. Superficial Muscles: Posterior Slide 6.44 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.21

55. Disorders relating to the Muscular System Muscular Dystrophy: inherited, muscle enlarge due to increased fat and connective tissue, but fibers degenerate and atrophy Duchenne MD: lacking a protein to maintain the sarcolemma Myasthemia Gravis: progressive weakness due to a shortage of acetylcholine receptors

56. Disorders of Muscle Tissue Muscle tissues experience few disorders –Heart muscle is the exception –Skeletal muscle – remarkably resistant to infection –Smooth muscle – problems stem from external irritants

57. Disorders of Muscle Tissue Muscular dystrophy – a group of inherited muscle destroying disease –Affected muscles enlarge with fat and connective tissue –Muscles degenerate Types of muscular dystrophy –Duchenne muscular dystrophy –Myotonic dystrophy

58. Disorders of Muscle Tissue Myofascial pain syndrome – pain is caused by tightened bands of muscle fibers Fibromyalgia – a mysterious chronic-pain syndrome –Affects mostly women –Symptoms – fatigue, sleep abnormalities, severe musculoskeletal pain, and headache

59. Developmental Aspects: Regeneration Cardiac and skeletal muscle become amitotic, but can lengthen and thicken Myoblast-like satellite cells show very limited regenerative ability Cardiac cells lack satellite cells Smooth muscle has good regenerative ability There is a biological basis for greater strength in men than in women Women’s skeletal muscle makes up 36% of their body mass Men’s skeletal muscle makes up 42% of their body mass

60. Developmental Aspects: Male and Female These differences are due primarily to the male sex hormone testosterone With more muscle mass, men are generally stronger than women Body strength per unit muscle mass, however, is the same in both sexes

61. Developmental Aspects: Age Related With age, connective tissue increases and muscle fibers decrease Muscles become stringier and more sinewy By age 80, 50% of muscle mass is lost (sarcopenia) Decreased density of capillaries in muscle Reduced stamina Increased recovery time Regular exercise reverses sarcopenia