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Muscle system

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Muscle system

  1. 1. Essentials of Human Anatomy & Physiology Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Seventh Edition Elaine N. Marieb Chapter 6 The Muscular System
  2. 2. The Muscular System Slide 6.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Muscles are responsible for all types of body movement – they contract or shorten and are the machine of the body </li></ul><ul><li>Three basic muscle types are found in the body </li></ul><ul><ul><li>Skeletal muscle </li></ul></ul><ul><ul><li>Cardiac muscle </li></ul></ul><ul><ul><li>Smooth muscle </li></ul></ul>
  3. 3. Characteristics of Muscles Slide 6.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Muscle cells are elongated (muscle cell = muscle fiber) </li></ul><ul><li>Contraction of muscles is due to the movement of microfilaments </li></ul><ul><li>All muscles share some terminology </li></ul><ul><ul><li>Prefix myo refers to muscle </li></ul></ul><ul><ul><li>Prefix mys refers to muscle </li></ul></ul><ul><ul><li>Prefix sarco refers to flesh </li></ul></ul>
  4. 4. Skeletal Muscle Characteristics Slide 6.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Most are attached by tendons to bones </li></ul><ul><li>Cells are multinucleate </li></ul><ul><li>Striated – have visible banding </li></ul><ul><li>Voluntary – subject to conscious control </li></ul><ul><li>Cells are surrounded and bundled by connective tissue = great force, but tires easily </li></ul>
  5. 5. Connective Tissue Wrappings of Skeletal Muscle Slide 6.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Endomysium – around single muscle fiber </li></ul><ul><li>Perimysium – around a fascicle (bundle) of fibers </li></ul>Figure 6.1
  6. 6. Connective Tissue Wrappings of Skeletal Muscle Slide 6.4b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Epimysium – covers the entire skeletal muscle </li></ul><ul><li>Fascia – on the outside of the epimysium </li></ul>Figure 6.1
  7. 7. Skeletal Muscle Attachments Slide 6.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Epimysium blends into a connective tissue attachment </li></ul><ul><ul><li>Tendon – cord-like structure </li></ul></ul><ul><ul><li>Aponeuroses – sheet-like structure </li></ul></ul><ul><li>Sites of muscle attachment </li></ul><ul><ul><li>Bones </li></ul></ul><ul><ul><li>Cartilages </li></ul></ul><ul><ul><li>Connective tissue coverings </li></ul></ul>
  8. 8. Smooth Muscle Characteristics Slide 6.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Has no striations </li></ul><ul><li>Spindle-shaped cells </li></ul><ul><li>Single nucleus </li></ul><ul><li>Involuntary – no conscious control </li></ul><ul><li>Found mainly in the walls of hollow organs </li></ul><ul><li>Slow, sustained and tireless </li></ul>Figure 6.2a
  9. 9. Cardiac Muscle Characteristics Slide 6.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Has striations </li></ul><ul><li>Usually has a single nucleus </li></ul><ul><li>Joined to another muscle cell at an intercalated disc </li></ul><ul><li>Involuntary </li></ul><ul><li>Found only in the heart </li></ul><ul><li>Steady pace! </li></ul>Figure 6.2b
  10. 10. Function of Muscles Slide 6.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Produce movement </li></ul><ul><li>Maintain posture </li></ul><ul><li>Stabilize joints </li></ul><ul><li>Generate heat </li></ul>
  11. 11. Microscopic Anatomy of Skeletal Muscle Slide 6.9a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Cells are multinucleate </li></ul><ul><li>Nuclei are just beneath the sarcolemma </li></ul>Figure 6.3a
  12. 12. Microscopic Anatomy of Skeletal Muscle Slide 6.9b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Sarcolemma – specialized plasma membrane </li></ul><ul><li>Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum </li></ul>Figure 6.3a
  13. 13. Microscopic Anatomy of Skeletal Muscle Slide 6.10a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Myofibril </li></ul><ul><ul><li>Bundles of myofilaments </li></ul></ul><ul><ul><li>Myofibrils are aligned to give distrinct bands </li></ul></ul><ul><ul><ul><li>I band = light band </li></ul></ul></ul><ul><ul><ul><li>A band = dark band </li></ul></ul></ul>Figure 6.3b
  14. 14. Microscopic Anatomy of Skeletal Muscle Slide 6.10b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Sarcomere </li></ul><ul><ul><li>Contractile unit of a muscle fiber </li></ul></ul>Figure 6.3b
  15. 15. Microscopic Anatomy of Skeletal Muscle Slide 6.11a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Organization of the sarcomere </li></ul><ul><ul><li>Thick filaments = myosin filaments </li></ul></ul><ul><ul><ul><li>Composed of the protein myosin </li></ul></ul></ul><ul><ul><ul><li>Has ATPase enzymes </li></ul></ul></ul>Figure 6.3c
  16. 16. Microscopic Anatomy of Skeletal Muscle Slide 6.11b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Organization of the sarcomere </li></ul><ul><ul><li>Thin filaments = actin filaments </li></ul></ul><ul><ul><ul><li>Composed of the protein actin </li></ul></ul></ul>Figure 6.3c
  17. 17. Microscopic Anatomy of Skeletal Muscle Slide 6.12a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Myosin filaments have heads (extensions, or cross bridges) </li></ul><ul><li>Myosin and actin overlap somewhat </li></ul>Figure 6.3d
  18. 18. Properties of Skeletal Muscle Activity (single cells or fibers) Slide 6.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Irritability – ability to receive and respond to a stimulus </li></ul><ul><li>Contractility – ability to shorten when an adequate stimulus is received </li></ul>
  19. 19. Nerve Stimulus to Muscles Slide 6.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Skeletal muscles must be stimulated by a nerve to contract (motor neruron) </li></ul><ul><li>Motor unit </li></ul><ul><ul><li>One neuron </li></ul></ul><ul><ul><li>Muscle cells stimulated by that neuron </li></ul></ul>Figure 6.4a
  20. 20. Nerve Stimulus to Muscles Slide 6.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Neuromuscular junctions – association site of nerve and muscle </li></ul>Figure 6.5b
  21. 21. Nerve Stimulus to Muscles Slide 6.15b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Synaptic cleft – gap between nerve and muscle </li></ul><ul><ul><li>Nerve and muscle do not make contact </li></ul></ul><ul><ul><li>Area between nerve and muscle is filled with interstitial fluid </li></ul></ul>Figure 6.5b
  22. 22. Transmission of Nerve Impulse to Muscle Slide 6.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Neurotransmitter – chemical released by nerve upon arrival of nerve impulse </li></ul><ul><ul><li>The neurotransmitter for skeletal muscle is acetylcholine </li></ul></ul><ul><li>Neurotransmitter attaches to receptors on the sarcolemma </li></ul><ul><li>Sarcolemma becomes permeable to sodium (Na + ) </li></ul>
  23. 23. Transmission of Nerve Impulse to Muscle Slide 6.16b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Sodium rushing into the cell generates an action potential </li></ul><ul><li>Once started, muscle contraction cannot be stopped </li></ul>
  24. 24. The Sliding Filament Theory of Muscle Contraction Slide 6.17a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Activation by nerve causes myosin heads (crossbridges) to attach to binding sites on the thin filament </li></ul><ul><li>Myosin heads then bind to the next site of the thin filament </li></ul>Figure 6.7
  25. 25. The Sliding Filament Theory of Muscle Contraction Slide 6.17b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>This continued action causes a sliding of the myosin along the actin </li></ul><ul><li>The result is that the muscle is shortened (contracted) </li></ul>Figure 6.7
  26. 26. The Sliding Filament Theory Slide 6.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.8
  27. 27. Contraction of a Skeletal Muscle Slide 6.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Muscle fiber contraction is “all or none” </li></ul><ul><li>Within a skeletal muscle, not all fibers may be stimulated during the same interval </li></ul><ul><li>Different combinations of muscle fiber contractions may give differing responses </li></ul><ul><li>Graded responses – different degrees of skeletal muscle shortening, rapid stimulus = constant contraction or tetanus </li></ul>
  28. 28. Muscle Response to Strong Stimuli Slide 6.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Muscle force depends upon the number of fibers stimulated </li></ul><ul><li>More fibers contracting results in greater muscle tension </li></ul><ul><li>Muscles can continue to contract unless they run out of energy </li></ul>
  29. 29. Energy for Muscle Contraction Slide 6.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Initially, muscles used stored ATP for energy </li></ul><ul><ul><li>Bonds of ATP are broken to release energy </li></ul></ul><ul><ul><li>Only 4-6 seconds worth of ATP is stored by muscles </li></ul></ul><ul><li>After this initial time, other pathways must be utilized to produce ATP </li></ul>
  30. 30. Energy for Muscle Contraction Slide 6.24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Direct phosphorylation </li></ul><ul><ul><li>Muscle cells contain creatine phosphate (CP) </li></ul></ul><ul><ul><ul><li>CP is a high-energy molecule </li></ul></ul></ul><ul><ul><li>After ATP is depleted, ADP is left </li></ul></ul><ul><ul><li>CP transfers energy to ADP, to regenerate ATP </li></ul></ul><ul><ul><li>CP supplies are exhausted in about 20 seconds </li></ul></ul>Figure 6.10a
  31. 31. Energy for Muscle Contraction Slide 6.26a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Anaerobic glycolysis </li></ul><ul><ul><li>Reaction that breaks down glucose without oxygen </li></ul></ul><ul><ul><li>Glucose is broken down to pyruvic acid to produce some ATP </li></ul></ul><ul><ul><li>Pyruvic acid is converted to lactic acid </li></ul></ul>Figure 6.10b
  32. 32. Energy for Muscle Contraction Slide 6.26b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Anaerobic glycolysis (continued) </li></ul><ul><ul><li>This reaction is not as efficient, but is fast </li></ul></ul><ul><ul><ul><li>Huge amounts of glucose are needed </li></ul></ul></ul><ul><ul><ul><li>Lactic acid produces muscle fatigue </li></ul></ul></ul>Figure 6.10b
  33. 33. Energy for Muscle Contraction Slide 6.25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Aerobic Respiration </li></ul><ul><ul><li>Series of metabolic pathways that occur in the mitochondria </li></ul></ul><ul><ul><li>Glucose is broken down to carbon dioxide and water, releasing energy </li></ul></ul><ul><ul><li>This is a slower reaction that requires continuous oxygen </li></ul></ul>Figure 6.10c
  34. 34. Muscle Fatigue and Oxygen Debt Slide 6.27 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>When a muscle is fatigued, it is unable to contract </li></ul><ul><li>The common reason for muscle fatigue is oxygen debt </li></ul><ul><ul><li>Oxygen must be “repaid” to tissue to remove oxygen debt </li></ul></ul><ul><ul><li>Oxygen is required to get rid of accumulated lactic acid </li></ul></ul><ul><li>Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less </li></ul>
  35. 35. Types of Muscle Contractions Slide 6.28 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Isotonic contractions </li></ul><ul><ul><li>Myofilaments are able to slide past each other during contractions </li></ul></ul><ul><ul><li>The muscle shortens </li></ul></ul><ul><li>Isometric contractions </li></ul><ul><ul><li>Tension in the muscles increases </li></ul></ul><ul><ul><li>The muscle is unable to shorten </li></ul></ul>
  36. 36. Muscle Tone Slide 6.29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Some fibers are contracted even in a relaxed muscle </li></ul><ul><li>Different fibers contract at different times to provide muscle tone </li></ul><ul><li>The process of stimulating various fibers is under involuntary control </li></ul>
  37. 37. Muscles and Body Movements Slide 6.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Movement is attained due to a muscle moving an attached bone </li></ul>Figure 6.12
  38. 38. Muscles and Body Movements Slide 6.30b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Muscles are attached to at least two points </li></ul><ul><ul><li>Origin – attachment to a moveable bone </li></ul></ul><ul><ul><li>Insertion – attachment to an immovable bone </li></ul></ul>Figure 6.12
  39. 39. Effects of Exercise on Muscle Slide 6.31 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Results of increased muscle use </li></ul><ul><ul><li>Increase in muscle size </li></ul></ul><ul><ul><li>Increase in muscle strength </li></ul></ul><ul><ul><li>Increase in muscle efficiency </li></ul></ul><ul><ul><li>Muscle becomes more fatigue resistant </li></ul></ul>
  40. 40. Types of Ordinary Body Movements Slide 6.32 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Flexion – decreases angle of joint and brings two bones closer together </li></ul><ul><li>Extension- opposite of flexion </li></ul><ul><li>Rotation- movement of a bone in longitudinal axis, shaking head “no” </li></ul><ul><li>Abduction/Adduction (see slides) </li></ul><ul><li>Circumduction (see slides) </li></ul>
  41. 41. Body Movements Slide 6.33 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.13
  42. 42. 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.
  43. 43. Types of Muscles Slide 6.35 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Prime mover – muscle with the major responsibility for a certain movement </li></ul><ul><li>Antagonist – muscle that opposes or reverses a prime mover </li></ul><ul><li>Synergist – muscle that aids a prime mover in a movement and helps prevent rotation </li></ul>
  44. 44. Naming of Skeletal Muscles Slide 6.36a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Direction of muscle fibers </li></ul><ul><ul><li>Example: rectus (straight) </li></ul></ul><ul><li>Relative size of the muscle </li></ul><ul><ul><li>Example: maximus (largest) </li></ul></ul>
  45. 45. Naming of Skeletal Muscles Slide 6.36b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Location of the muscle </li></ul><ul><ul><li>Example: many muscles are named for bones (e.g., temporalis ) </li></ul></ul><ul><li>Number of origins </li></ul><ul><ul><li>Example: triceps (three heads) </li></ul></ul>
  46. 46. Naming of Skeletal Muscles Slide 6.37 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings <ul><li>Location of the muscles origin and insertion </li></ul><ul><ul><li>Example: sterno (on the sternum) </li></ul></ul><ul><li>Shape of the muscle </li></ul><ul><ul><li>Example: deltoid (triangular) </li></ul></ul><ul><li>Action of the muscle </li></ul><ul><ul><li>Example: flexor and extensor (flexes or extends a bone) </li></ul></ul>
  47. 47. Head and Neck Muscles Slide 6.38 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.14
  48. 48. Trunk Muscles Slide 6.39 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.15
  49. 49. Deep Trunk and Arm Muscles Slide 6.40 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.16
  50. 50. Muscles of the Pelvis, Hip, and Thigh Slide 6.41 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.18c
  51. 51. Muscles of the Lower Leg Slide 6.42 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.19
  52. 52. Superficial Muscles: Anterior Slide 6.43 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.20
  53. 53. Superficial Muscles: Posterior Slide 6.44 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.21
  54. 54. Disorders relating to the Muscular System <ul><li>Muscular Dystrophy: inherited, muscle enlarge due to increased fat and connective tissue, but fibers degenerate and atrophy </li></ul><ul><li>Duchenne MD: lacking a protein to maintain the sarcolemma </li></ul><ul><li>Myasthemia Gravis: progressive weakness due to a shortage of acetylcholine receptors </li></ul>

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