5.a&p i muscle2010


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5.a&p i muscle2010

  1. 1. Muscle Structure and Physiology Marieb: Chap. 9
  2. 2. Muscles <ul><li>I. Introduction </li></ul><ul><ul><li>1. Types of muscles: </li></ul></ul><ul><ul><ul><li>a) Skeletal = Voluntary Striated </li></ul></ul></ul><ul><ul><ul><li>b) Cardiac = Involuntary Striated </li></ul></ul></ul><ul><ul><ul><li>c) Visceral = Involuntary Smooth/Nonstriated </li></ul></ul></ul><ul><ul><li>2. Properties: </li></ul></ul><ul><ul><ul><li>a) respond to stimulus with contraction = excitability </li></ul></ul></ul><ul><ul><ul><li>b) passively stretched = extensible </li></ul></ul></ul><ul><ul><ul><li>c) return to original shape or length = elasticity </li></ul></ul></ul><ul><ul><li>3. Functions: </li></ul></ul><ul><ul><ul><li>a) motion b) posture </li></ul></ul></ul><ul><ul><ul><li>c) heat production d) stabilize joints </li></ul></ul></ul>
  3. 3. Fig. 9.1
  4. 4. II. Skeletal Muscle A. Extramuscular Tissue <ul><li>1. Fascia - sheets of fibrous CT wrapped around muscle </li></ul><ul><li>2. Epimysium - fibrous CT, extension of fascia </li></ul><ul><li>3. Perimysium - separates muscle into individual bundles or fascicles </li></ul><ul><li>4. Endomysium - separates into individual muscle cells or fibers </li></ul><ul><li>5. Tendon - </li></ul><ul><ul><li>a) cordlike CT connected to epimysium & bone </li></ul></ul><ul><ul><li>b) aponeurosis - broad, flat band connected to muscle or bone </li></ul></ul>
  5. 5. II. Skeletal muscle = Voluntary Striated <ul><ul><li>6. Blood Vessels </li></ul></ul><ul><ul><ul><li>a) outside perimysium but below or under epimysium = larger vessels </li></ul></ul></ul><ul><ul><ul><li>b) capillaries and small branches associated with endomysium layer </li></ul></ul></ul><ul><ul><li>7. Nervous Tissue </li></ul></ul><ul><ul><ul><li>a) Travel with larger blood vessels </li></ul></ul></ul><ul><ul><ul><li>b) branches to individual muscles or groups of muscles </li></ul></ul></ul><ul><ul><li>8. Motor Unit - single motor neuron plus all muscle fibers it stimulates </li></ul></ul><ul><ul><ul><li>1 neuron can stimulate </li></ul></ul></ul><ul><ul><ul><ul><li>10 separate muscle fibers </li></ul></ul></ul></ul><ul><ul><ul><ul><li>150 separate muscle fibers </li></ul></ul></ul></ul><ul><ul><ul><ul><li>500 separate muscle fibers (Behavior?) </li></ul></ul></ul></ul>
  6. 6. <ul><li>9. Neuromuscular Junction (NMJ) </li></ul><ul><ul><li>Point of contact or communication between neuron and muscle </li></ul></ul><ul><li>10. Motor End Plate </li></ul><ul><ul><li>Specialized portion of muscle membrane at a NMJ </li></ul></ul>Fig. 9.13
  7. 7. B. Ultrastructure of Skeletal Muscle <ul><ul><li>1. Sarcolemma - cell membrane </li></ul></ul><ul><ul><li>2. Sarcoplasm - cytoplasm </li></ul></ul><ul><ul><li>3. Multinucleated with many mitochondria </li></ul></ul><ul><ul><li>4. Sarcoplasmic Reticulum (SR) </li></ul></ul><ul><ul><ul><li>Smooth ER </li></ul></ul></ul><ul><ul><ul><li>SR usually in longitudinal direction </li></ul></ul></ul><ul><ul><ul><li>If SR is perpendicular to surface, right angles, known as Transverse SR or T-Tubules </li></ul></ul></ul><ul><ul><ul><li>Triad = one T-Tubule plus 2 SR </li></ul></ul></ul>
  8. 8. Fig. 9.5 5. Endomysium surrounding single muscle fiber
  9. 9. <ul><ul><li>5. Endomysium surrounds single muscle fiber/cell </li></ul></ul><ul><ul><ul><li>Up to 30 cm long and 10-100um diameter </li></ul></ul></ul><ul><ul><ul><li>Each muscle cell contains many myofibrils </li></ul></ul></ul><ul><ul><ul><ul><li>Myofibril (1-2um) = bundles of myofilaments </li></ul></ul></ul></ul><ul><ul><ul><li>Myofilaments = individual muscle filaments </li></ul></ul></ul><ul><ul><ul><ul><li>Thick = myosin </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Thin = actin or troponin or tropomyosin </li></ul></ul></ul></ul><ul><ul><ul><li>Sarcomere = contractile unit, segment of a myofibril </li></ul></ul></ul><ul><ul><li>6. Myofilament Information </li></ul></ul>
  10. 10. Fig. 9.2a/b
  11. 12. Fig. 9.3
  12. 13. Fig. 9.3
  13. 14. Fig. 9.4
  14. 15. <ul><li>6. Myofilament Information </li></ul><ul><ul><li>a) Myosin - rod like tail terminating in two globular heads (sites of cross bridges) </li></ul></ul><ul><ul><ul><li>Each thick filament = 200 myosin molecules with tails in the center and heads facing outwards on each side (away from H zone) </li></ul></ul></ul><ul><ul><li>b) Actin - thin filaments that contain active sites where myosin bridges attach </li></ul></ul><ul><ul><li>c) Regulatory proteins on actin </li></ul></ul><ul><ul><ul><li>Tropomyosin - spiral around actin and block actin sites to bind myosin at rest </li></ul></ul></ul><ul><ul><ul><li>Troponin - 3 sites: bind to actin, tropomyosin and calcium </li></ul></ul></ul><ul><ul><li>d) Elastic (Titin) filaments - extend from Z disc to myosin to anchor myosin in place and help help muscle spring back after being stretched </li></ul></ul>
  15. 16. <ul><li>7. Anatomy of Relaxed muscle </li></ul><ul><ul><li>Sarcomere - region of a myofibril between two successive Z discs/lines </li></ul></ul><ul><ul><li>Z disc = anchors the thin actin filaments </li></ul></ul><ul><ul><li>I band = extends from both sides of a Z disc, contains only thin actin filaments </li></ul></ul><ul><ul><li>A band = boundary of thicker myosin filaments plus contain some thin actin from I band </li></ul></ul><ul><ul><li>H zone of A band = less dense area where actin ends but myosin continues </li></ul></ul><ul><ul><li>M line of center of H zone = protein strands that stabilize myosin together </li></ul></ul>
  16. 17. Fig. 9.2 c/d
  17. 18. <ul><li>C. Sliding filament model of contraction Huxley 1954 </li></ul><ul><ul><li>1. Thin actin filaments slide past the thicker myosin due to activation of myosin cross bridges to sites on actin </li></ul></ul><ul><ul><li>2. Each cross bridge attaches and reattaches to move actin towards H zone </li></ul></ul><ul><ul><li>3. H zone disappears </li></ul></ul><ul><ul><li>4. I band shortens as Z discs move closer to each other </li></ul></ul><ul><ul><li>5. A bands move closer to each other but do not change length since length of myosin does not change, only actin sliding over myosin </li></ul></ul>
  18. 19. Fig. 9.6 - 1 M
  19. 20. Fig. 9.6
  20. 21. Fig. 9.6
  21. 22. <ul><li>D. Physiology of Contraction </li></ul><ul><ul><li>1. ATP = energy chemical for contraction </li></ul></ul><ul><ul><ul><li>Hydrolysis of ATP </li></ul></ul></ul><ul><ul><ul><li>ATP + H 2 O ADP + P + ENERGY </li></ul></ul></ul><ul><ul><ul><li>Energy used by cell for active transport, synthesis, and muscle contraction </li></ul></ul></ul><ul><ul><ul><li>Dehydration Synthesis of ATP </li></ul></ul></ul><ul><ul><ul><li>ADP + P + ENERGY ATP + H 2 O </li></ul></ul></ul><ul><ul><ul><li>Energy supplied from cellular respiration </li></ul></ul></ul>
  22. 23. <ul><li>D. Physiology of Contraction </li></ul><ul><ul><li>2. At rest - </li></ul></ul><ul><ul><ul><li>a) Calcium stored in the SR (not free in the sarcoplasm) </li></ul></ul></ul><ul><ul><ul><li>b) ATP attached to the myosin cross bridge heads in relaxed position (not power position) </li></ul></ul></ul><ul><ul><ul><li>c) troponin-tropomyosin attached to actin filament - blocking the actin site for the myosin head :. NO ACTIN-MYOSIN ATTACHMENTS AT THE CROSS BRIDGES - NO TENSION </li></ul></ul></ul>
  23. 24. FIG. 9.11
  24. 25. <ul><ul><li>3. Nerve becomes active/excites </li></ul></ul><ul><ul><ul><li>a) conducts electrical charge down motor neuron axon towards terminal branch endings at neuromuscular junction </li></ul></ul></ul><ul><ul><ul><li>b) in the ending of the neuron, vesicles are present that contain the neurotransmitter chemical - nerves that stimulate skeletal muscles contain acetylcholine (ACh) </li></ul></ul></ul><ul><ul><ul><li>c) electrical current dies out in nerve ending but vesicles move towards nerve membrane and release ACh contents into NMJ via exocytosis </li></ul></ul></ul>
  25. 26. FIG. 9.9 modified
  26. 27. Fig.9.11 modified
  27. 28. <ul><ul><li>4. ACh diffuses across the space towards muscle membrane of motor end plate (net diffusion) where there are receptors for ACh on the muscle membrane </li></ul></ul><ul><ul><ul><li>ACh will change membrane permeability to sodium and muscle becomes electrically excited and active in this region </li></ul></ul></ul><ul><ul><li>5. Excitation - Contraction coupling - the electrical changes on the muscle membrane lead to sliding of the myofilaments </li></ul></ul>
  28. 29. <ul><ul><li>5. Excitation - Contraction Coupling </li></ul></ul><ul><ul><ul><li>a) electrical changes on surface of sarcolemma spread down the T- tubules to the inner core of the muscle </li></ul></ul></ul><ul><ul><ul><li>b) remember - T-tubules meet the horizontal SR and form a triad </li></ul></ul></ul><ul><ul><ul><li>c) electrical changes of the SR cause Calcium (Ca 2+ ) to be released into the sarcoplasm by opening Ca 2+ channels of the SR </li></ul></ul></ul><ul><ul><ul><li>Ca 2+ is available to bind to the myofilaments </li></ul></ul></ul><ul><ul><li>6. Calcium is free in the sacroplasm </li></ul></ul><ul><ul><ul><li>a) Ca 2+ activates the ATPase activity on the myosin head and powers the bending of the head </li></ul></ul></ul>
  29. 30. Fig.9.11
  30. 31. <ul><ul><li>6b) Ca 2+ also displaces the troponin - tropomyosin complex from the actin binding sites (see Figure 9.10 & 11) </li></ul></ul><ul><ul><li>c) actin-myosin cross bridge forms and flips backwards pulling the actin past the myosin towards the center of the sarcomere </li></ul></ul><ul><ul><li>d) TENSION develops </li></ul></ul><ul><ul><li>e) one working stroke of head shortens muscle 1% - usual muscle shortening 30 to 35% - therefore each myosin cross bridge attaches and reattaches several times during a contraction </li></ul></ul>
  31. 33. <ul><ul><li>7. Nerve stops firing and stops releasing ACh </li></ul></ul><ul><ul><ul><li>As long as ACh is in gap - keeps stimulating muscle and Ca 2+ </li></ul></ul></ul><ul><ul><ul><li>ACh is destroyed in the space by an enzyme always present - acetylcholinesterase </li></ul></ul></ul><ul><ul><ul><li>Therefore - muscle membrane no longer electrically active and this cessation causes the free Ca 2+ to be transported BACK into the SR spaces via an ATP-dependent active pump </li></ul></ul></ul><ul><ul><ul><li>NO FREE CALCIUM </li></ul></ul></ul>
  32. 34. <ul><ul><li>8. Without free Ca 2+ - troponin-tropomyosin reoccupy the active site that binds myosin heads and cross bridges are broken and not reformed. </li></ul></ul><ul><ul><ul><li>a) ATP is resynthesized and occupy the myosin binding sites </li></ul></ul></ul><ul><ul><ul><li>b) since cross bridges were broken - tension is lost and muscle returns to its original resting length </li></ul></ul></ul><ul><ul><li>Myostenia gravis - problem with ACh receptor destruction </li></ul></ul><ul><ul><li>Rigor mortis - explain it????? </li></ul></ul><ul><ul><ul><li>3-4 hours muscle stiffens, maximum by 12 hrs </li></ul></ul></ul><ul><ul><ul><li>Dissipates over the next 2-3 days </li></ul></ul></ul>
  33. 35. <ul><ul><li>9. Creatine Phosphate </li></ul></ul><ul><ul><ul><li>Muscles cannot store adequate ATP for continues muscle contractions </li></ul></ul></ul><ul><ul><ul><li>At rest: </li></ul></ul></ul><ul><ul><ul><li>ADP + P + Energy = ATP stored and on myosin </li></ul></ul></ul><ul><ul><ul><li>ATP + creatine = creatine-phosphate + ADP </li></ul></ul></ul><ul><ul><ul><li>Exercise: </li></ul></ul></ul><ul><ul><ul><li>ATP = ADP + P + Energy </li></ul></ul></ul><ul><ul><ul><li>Creatine-phosphate + ADP =creatine + ATP </li></ul></ul></ul>
  34. 36. <ul><li>E. Skeletal Muscle Physiology </li></ul><ul><ul><li>1. Single Twitch Phenomenon (lab) </li></ul></ul><ul><ul><ul><li>a) single stimulus - threshold </li></ul></ul></ul><ul><ul><ul><li>Weakest stimulus that causes a muscle contraction </li></ul></ul></ul><ul><ul><ul><li>b) latent period (01. sec) - time between the stimulation and actual mechanical contraction of muscle </li></ul></ul></ul><ul><ul><ul><li>chemical / electrical change / Calcium </li></ul></ul></ul><ul><ul><ul><li>any tendon slack taken up first </li></ul></ul></ul><ul><ul><ul><li>c) contraction phase - developing tension (.04s) </li></ul></ul></ul><ul><ul><ul><li>d) relaxation phase (.05 sec) - calcium upt6ake and breaking cross bridges </li></ul></ul></ul>
  35. 37. <ul><li>e) fast muscle = 0.03 sec (insect 0.003 sec) </li></ul><ul><li>slow muscles = seconds </li></ul><ul><li>f) refractory period - no response to second equal stimulus, but a response to a stronger stimulus </li></ul>Fig. 9.14
  36. 38. <ul><li>g) 1) slow oxidative muscle - posture, marathon </li></ul><ul><ul><li>red muscles (myoglobin) + mitochondria + abundant capillaries = high aerobic activity but slow ATPase activity </li></ul></ul><ul><ul><li>2) fast glycolytic fibers - quick powerful movement - hitting baseball </li></ul></ul><ul><ul><li>White muscle low in myoglobin, more anaerobic and faster ATPase activity </li></ul></ul><ul><ul><li>Most muscle have a mixture of both </li></ul></ul><ul><ul><li>Table 9.2 textbook </li></ul></ul>
  37. 39. <ul><li>2. All or None Phenomenon </li></ul><ul><ul><li>a) threshold - individual fibers respond maximally when stimulated </li></ul></ul><ul><ul><li>b) influenced by : </li></ul></ul><ul><ul><ul><li>Temperature </li></ul></ul></ul><ul><ul><ul><li>Products of metabolism </li></ul></ul></ul><ul><ul><ul><li>Oxygen availability </li></ul></ul></ul><ul><ul><ul><li>Fatigue </li></ul></ul></ul><ul><ul><li>c) muscle contain many individual fibers </li></ul></ul><ul><ul><ul><li>Each fiber = all or none </li></ul></ul></ul><ul><ul><ul><li>Entire muscle has graded response determined by the number of fibers contracting </li></ul></ul></ul><ul><ul><ul><li>Entire muscle has a maximum response (100% fibers) </li></ul></ul></ul>
  38. 41. Fig. 9.16/17
  39. 42. <ul><li>3. Summation - 2 consecutive stimuli with second response greater than the first </li></ul><ul><li>4. Staircase or Treppe - stimulate muscle second time after it relaxes and compare tension </li></ul>Fig. 9.15b
  40. 43. <ul><li>5. Tetanus - physiological response </li></ul><ul><ul><li>a) many rapid responses to prevent relaxation (2) </li></ul></ul><ul><ul><li>b) fusion of twitches - continuous sustained contraction (4) </li></ul></ul><ul><ul><li>c) partial or incomplete tetanus - contractions do not fuse (3) </li></ul></ul><ul><li>6. Tonic Contraction </li></ul><ul><ul><li>a) some cells contracted, others relaxed, interchange </li></ul></ul><ul><ul><li>Posture </li></ul></ul><ul><ul><li>Flaccid - less than normal tone to muscle </li></ul></ul>Fig. 9.15-9.16
  41. 44. <ul><li>7. Isotonic </li></ul><ul><ul><li>a) same tone or tension </li></ul></ul><ul><ul><li>b) change in length during contraction </li></ul></ul><ul><ul><li>c) pick up a book </li></ul></ul>Fig. 9.18a
  42. 45. <ul><li>8. Isometric </li></ul><ul><ul><li>a) same length </li></ul></ul><ul><ul><li>b) develop or change tension </li></ul></ul><ul><ul><li>c) try to left heavy object, push wall </li></ul></ul>Fig. 9.18b
  43. 46. <ul><li>III. Cardiac muscle </li></ul><ul><ul><li>1. Involuntary, striated muscle </li></ul></ul><ul><ul><li>2. Single nucleus, branched </li></ul></ul><ul><ul><li>3. Intercalated discs </li></ul></ul><ul><ul><ul><li>Area of low resistance to electrical flow of current - network contraction response </li></ul></ul></ul><ul><ul><li>4. Intrinsic rhythm - normal rate of pacemaker = 120+ per minute </li></ul></ul><ul><ul><ul><li>Vagus nerve slows down intrinsic pacemaker to 60-80 beats per minute </li></ul></ul></ul><ul><ul><li>5. Refractory period - rest </li></ul></ul><ul><ul><ul><li>No tetanus possible </li></ul></ul></ul><ul><ul><ul><li>High rate = fibrillation </li></ul></ul></ul>
  44. 47. Fig. 18.11
  45. 48. <ul><li>6. Skeletal vs. cardac contraction </li></ul><ul><ul><li>Cardiac has longer tension due to calcium involved from both SR and extracellular environment </li></ul></ul>Fig. 18.12
  46. 49. <ul><li>IV. Smooth Muscle </li></ul><ul><ul><li>1. Involuntary, nonstriated muscle </li></ul></ul><ul><ul><li>a) actin & myosin poorer organization of fibers </li></ul></ul><ul><ul><li>b) fibers attached to membrane or lattice in sarcoplasm </li></ul></ul><ul><ul><li>c) SR less developed </li></ul></ul><ul><ul><li>d) spindle shaped </li></ul></ul>Fig. 9.28a/b
  47. 51. <ul><ul><li>2. Type of Contraction </li></ul></ul><ul><ul><ul><li>Slow contraction due to poor arrangement of fibers </li></ul></ul></ul><ul><ul><ul><li>Does not fatigue </li></ul></ul></ul><ul><ul><ul><li>Tonic type of contraction </li></ul></ul></ul><ul><ul><ul><li>Calcium involved from </li></ul></ul></ul><ul><ul><ul><ul><li>SR </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Extracellular </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Movement is slower since there are no T-Tubules </li></ul></ul></ul></ul><ul><ul><ul><li>See Fig. 9.29 </li></ul></ul></ul>
  48. 52. <ul><li>3. Visceral/single unit vs. Multiunit </li></ul><ul><li>a) sheets lining blood vessels a) larger blood vessels and walls of organs airways, eye muscles, arrector pili muscles </li></ul><ul><li>b) tight junctions between muscle cells </li></ul><ul><li>c) one nerve controls many different muscle cells, wave-like contraction </li></ul><ul><li>c) individual muscles with separate motor nerves </li></ul>