chap 10

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nadiaessaqi
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chap 10
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2012-06-28 23:14:20
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  1. characteristics of skeletal muscle
    attached to skeletal system, allow movement,composes muscular system,volentary muscle
  2. 6 functions of skeletal muscle
  3. 1.Produce skeletal movement 2.Maintain posture and body position 3.Support soft tissues 4.Guard entrances and exits 5.Maintain body temperature6.Store nutrient reserves
  4. what tiisues are found in skeletal muscles
  5. •Muscle tissue(muscle cells or fibers)
    •Connective tissues •Nerves •Blood vessels
  6. what is epimysium?
    • 1. Exterior collagen layer
    • •Connected to deep fascia à separates muscle from surrounding tissues
  7. what is perimysium?
    • 2.Surrounds muscle fiber bundles (fascicles)
    • •Contains blood vessel and nerve supply to fascicles
  8. Endomysium
    • 3.Surrounds individual muscle cells (muscle fibers)
    • •Contains capillaries and nerve fibers contacting muscle cells
    • •Contains myosatellite cells (stem cells) that repair damage
  9. what happens to the connective tissue at the end of a muscle
    • •Endomysium, perimysium, and epimysium come together:
    • •At ends of muscles to form connective tissue attachment to bone matrix
    • •Tendon (bundle) or aponeurosis (sheet)
  10. Muscles have extensive vascular systems that?
  11. •Supply large amounts of oxygen, supply nutrients, and carry away wastes
  12. about Skeletal Muscle Cells
    • •Are very long (30 cm / 12 in)
    • •Develop through fusion of embryonic cells (myoblasts)
    • •Become very large
    • •Contain hundreds of nuclei
  13. location of sarcolemma
    • •The cell membrane of a muscle fiber (cell)
    • •Surrounds the sarcoplasm (cytoplasm of muscle fiber)
    • •A change in transmembrane potential begins contractions
  14. location of transverse tubles
  15. •Narrow tubes that are continuous with the sarcolemma•Transmit action potential through cell
    • •Allow entire muscle fiber to contract simultaneously
    • •Have same properties as sarcolemma
  16. myofibrils
  17. •Lengthwise subdivisions within muscle fiber
    • •Made up of bundles of protein filaments (myofilaments)
    • •Myofilaments are responsible for muscle contraction
    • •Types of myofilaments:
  18. thin filaments
  19. •Made of the protein actin
  20. thick filaments
  21. •Made of the protein myosin
  22. Sarcoplasmic Reticulum (SR)
    • •A membranous structure surrounding each myofibril
    • •Helps transmit action potential to myofibrilSimilar in structure to smooth endoplasmic reticulum
    • •Forms chambers (terminal cisternae) attached to T tubules
  23. structural relationship between terminal cisternae of the sr and the  tubules
    a triad is made of 1 t-tubule 2 terminal cistenae
  24. function performed by triad
    release ca2+(via ion pumps) release Ca+ into sarameres 2 begin muscle contraction
  25. sarcomere
    • Sarcomeres are the contractile units of muscle (myofibrils surround)
    • •Structural units of myofibrils
    • •Form visible patterns (stripes, striations) within myofibrils
    • •Alternating dark, thick filaments (A bands) and light, thin filaments (I bands)
  26. •The A Band contains
    • m band
    • •The center of the A band
    • •At midline of sarcomere
    • h band
    • •Lighter area around the M line
    • •Has thick filaments but no thin filaments
  27. zone of overlap
  28. •The densest, darkest area on a light micrograph
    •Where thick and thin filaments overlap
  29. the i band contains
    • zline
    • •The centers of the I bands
    • •At two ends of sarcomere
    • Titin
    • •Are strands of protein
    • •Reach from tips of thick filaments to the Z line
    • •Stabilize the filaments
  30. 4 proteins of thin filiments
    f-actin(filamentous),nebulin,tropomysin,troponin
  31. •Troponin
  32. •Troponin binds tropomyosin to actin
    •Controlled by Ca2+
  33. tropomyosin
  34. •Tropomyosin prevents actin–myosin interaction
  35. nebulin
  36. •Nebulin holds F-actin strands together
  37. •F-actin (filamentous)
  38.  •F-actin (filamentous) is two twisted rows of globular G-actin
    •The active sites of actin bind to myosin
  39. thick filiments contain what 2 proteins
  40. Thick Filaments
    • •Contain about 300 twisted myosin subunits
    • •Contain titin strands that recoil after stretching
  41. how does the myosin moilecule work
    • The mysosin molecule
    • •Tail à binds to other myosin molecules
    • •Head à made of two globular protein subunits
    • •Reaches the nearest thin filament
  42. what happens during contraction
    what happens•During contraction, myosin heads: •Interact with actin filaments, forming cross-bridges •Pivot, producing motion
  43. initiating contraction
  44. •Ca2+ binds troponin molecule
    • •Troponin–tropomyosin complex changes shape
    • •Exposes active site of F-actin
  45. sliding filiments muscle contraction
    • •Sliding filament theory
    • •Thin filaments of sarcomere slide toward M line, alongside thick filaments
    • •The width of A zone (dark area of thick filaments) stays the same
    • •Z lines move closer together
  46. the process of contraction involves
    • •Neural stimulation of sarcolemma
    • Causes excitation–contraction coupling
    • •Muscle fiber contraction
    • •Interaction of thick and thin filaments
    • •Tension production
  47. neuromuscular junction
    • •Special intercellular connection between the nervous system and skeletal muscle fiber
    • •Controls calcium ion release into the sarcoplasm
  48. Excitation–Contraction Coupling
    • •Action potential reaches a triad
    • •Releasing Ca2+
    • •Triggering contraction
    • •Requires myosin heads to be in “cocked” position
    • •Loaded by ATP energy
  49. process of contraction involves
    • •Neural stimulation of sarcolemma
    • •Causes excitation–contraction coupling
    • •Muscle fiber contraction
    • •Interaction of thick and thin filaments
    • •Tension production
  50. contraction cycle
    • 1.contraction cycle begins
    • 2.Active-Site Exposure 3.Cross-Bridge Formation 4.Myosin Head Pivoting 5.Cross-Bridge Detachment 6.Myosin Reactivation
  51. how is atp utalized during contraction cycle
    adp of myosin head is released when cocked. it needs atp to detach and splits atp to adp releasing energy to recock
  52. contraction duration depends on
    • •Duration of neural stimulus
    • •Number of free calcium ions in
    • sarcoplasm
    • Availability of ATP
    • relaxation

    • •Ca2+
    • concentrations fall
    • •Ca2+
    • detaches from troponin
    • •Active
    • sites are re-covered by tropomyosin
  53. tension production during muscle contraction
    • •As sarcomeres shorten, muscle pulls
    • together, producing tension
    • •Muscle shortening can occur at both
    • ends of the muscle, or at only one end of the muscle
    • •depends on the way the muscle is
    • attached at the ends
  54. skeletal muscle contraction and relaxation
    • •Contraction is an active process
    • •SR releases Ca2+ when a motor neuron stimulates the
    • muscle fiber
    • •Free Ca2+ in the sarcoplasm triggers
    • contraction
    • •Skeletal muscle fibers shorten as thin
    • filaments slide between thick filaments
    • •Relaxation and return to resting length
    • are passive
  55. tension production of muscle fibers
    • •Length–Tension Relationships
    • •Number of pivoting cross-bridges
    • depends on:
    • •Amount of overlap between thick and
    • thin fibers
    • •Optimum overlap produces greatest
    • amount of tension
    • •Too much or too little reduces
    • efficiency
    • 75-130normal resting of length
  56. A single neural stimulation produces
    • •A single contraction or twitch
    • •Which lasts about                                          7–100
    • msec.
    • sustained muscular contractions
    • •Require many repeated
    • stimuli
  57. latient 2msec
    • •The action potential moves through sarcolemma
    • •Causing Ca2+ release
  58. contraction phase 15msec
    • •Calcium ions bind
    • •Tension builds to peak
  59. relaxation phase 25msec
    • •Ca2+ levels fall
    • •Active sites are covered and tension
    • falls to resting levels
  60. treppe(stair-step
    repeated stimulus immediatly after relaxion phase frequency <50sec
  61. wave summation(increasing tension
    repeated stimulus before the end of relaxation phase frequency >50sec
  62. incomplete tenus
    rapid stimulation continues muscles not allowed to relax *almost reach max level of tension
  63. complete tetnus
    stimulation high enough *relaxation stage completely eliminated (producing maximum tension)
  64. how the frequency of neural stimulation controls tension production 
  65. how is the total muscle fiber activity controlled for an entire skeletal muscle
    internal tension by fibers,number of muscle fibers stimulated. MOTOR units contain hundreds of muscle fibers contracting at same time that r controlled by a single neuron
  66. recruitment in motor units and tension production
    in whole muscle smoooth motion and increasing tension r produced by slowly increasing number of motor units stimulated. max tension acheived when all motor units reach tetanus,can only be sustained 4 a very short time
  67. sustained tension
    less than max tension ,allows motor units to rest in rotation
  68. muscle tone
    normal tension of muscle at rest,muscle units maintain body position without motion,increasing muscle tone increases metabolic energy used,even at rest
  69. isotonic contraction
    changes length resulting in motion
  70. concentric contraction
    if load is less than muscle tension muscle shortens
  71. eccentric contraction
    if muscle tension is less than load (muscle lengthens
  72. isometric
    skeltetal muscl does not change length,still developing tension
  73. load and speed of contraction
    inversly related . the heavier the load. the longer it takes shortening to begin and the less the muscle will shorten
  74. how does muscle return to resting length after contraction
    • 1elastic forces (tendons ligaments) expands sarcomeres to resting length.
    • 2opposing muscle contractions reverse the direction of the original motion(opposing skeletal muscle pairs
    • 3gravity can take the place of opposing muscle contraction to return muscle to its resting state
  75. fuels of power contraction
    • atp 2sec 10twitches
    • cp 15secs 70 twitches
    • glycogen 130secs 670twitches
    • aerobic 2400secs 12,000twitches
  76. creatine phosphate
    • stores excess atp
    • used to recharge adp to atp usinf enzyme creatine kinase
  77. energy use of resting muscle,during light activity, and at peak activity
    • (muscles at rest) metabolize fatty acids,store glycogen,build cp reserves
    • aerobic metabolism(light activity)34 per glucose molecule
    • anarobic 2 per glucose during peak muscular
  78. muscle fatigue
    when muscles can no longer perform a req activity, they r fatigued
  79. results of muscle fatigue
    depletion of metabolic reserves ,damage to sarcolemma and sacroplasmic reticulum,low ph,muscle exhaustion and pain
  80. recovery period
    the time required after exertion for muscles to return to normal. oxygen becomes available, mitochondrial resumes

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