A&P Chapter 10/11 - Muscles

  1. functions of skeletal muscle
    • heat generation
    • movement
    • posture
    • breathing
  2. properties of skeletal muscle
    • excitability/irritability
    • contractility
    • extensibility
    • elasticity
  3. excitability/irritability
    ability to respond to a stimulus
  4. contractility
    ability to shorten if stimulated
  5. extensibility
    ability to stretch if pulled
  6. elasticity
    ability to return to original shape after stretching
  7. muscle facts
    • usually work in pairs
    • work together or oppose each other
    • only pull - never push
    • should only shorten - never extend beyond original length
    • insertion should only move toward origin
  8. insertion
    • most movable part of a muscle that is attached to the most movable bone
    • usually farthest from trunk
  9. origin
    • least movable part of a muscle that is attached to the least movable bone
    • usually closest to the trunk
  10. gaster
    • aka body / belly
    • middle main part of a muscle
  11. agonist
    • aka prime mover
    • muscle in a group that produces a desired movement
  12. antagonist
    muscle in a group that reverses a specific movement
  13. agonist/antagonist facts
    • usually on opposite sides of a joint over which they act
    • when prime mover contracts, agonist relaxes
    • may stay partially contracted to produce smooth movement
  14. synergists
    muscles that help prime movers and antagonists function and help eliminate unnecessary movement at the joint
  15. fixators
    muscles that stabilize the prime mover to cause the desired movement
  16. skeletal muscle anatomy
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  17. epimysium
    membrane that covers the entire muscle
  18. fascicles
    bundles of skeletal muscle fibers
  19. perimysium
    membrane that surrounds fascicles
  20. muscle fibers
    muscle cells
  21. endomysium
    membrane that surrounds individual muscle fibers
  22. myofibrils
    contractile organelles of skeletal muscle
  23. sarcomere
    smallest part of a muscle that is capable of contracting
  24. sarco- / myo-
    prefix for muscle
  25. sarcolemma
    cell membrane of a muscle cell
  26. sarcoplasm
    muscle cytoplasm
  27. sarcoplasmic reticulum
    ER of a muscle cell
  28. Z disk
    dense region of cytoplasm that separates sarcomeres in a muscle
  29. actin
    thin protein filaments that directly attach to z-disk
  30. myosin
    thick protein filaments that slightly overlap actin on each side
  31. titin
    thin elastic protein that attaches myosin to Z disk
  32. I band
    contains actin and titin (no myosin)
  33. A band
    contains myosin and overlapping actin
  34. H zone
    part of A band containing only myosin
  35. M line
    imaginary line through middle of sarcomere
  36. active sites
    only in I band
  37. tropomyosin
    covers active sites in relaxed sarcomere
  38. cross bridges
    golf club shaped proteins on myosin
  39. motor unit
    motor neuron plus part of muscle that it stimulates
  40. neuromuscular junction
    • where neuron and muscle join
    • composed of axon terminal, synapse, and motor end plate

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  41. motor neuron
    any nerve cell that carries impulses from brain out to a muscle
  42. axon terminal
    distal expanded part of an axon
  43. synaptic end bulb
    expanded end of the axon
  44. synaptic vesicles
    tiny sacs inside bulbs filled with chemicals called neurotransmitters (NT)
  45. neurotransmitters
    allow neurons to communicate with muscle
  46. acetylcholine
    only NT associated with muscle
  47. synapse
    space between axon terminal and muscle
  48. T tubles
    deep indentations in sarcolemma
  49. motor end plate
    part of muscle directly across from axon terminal that stimulates it
  50. naming of muscles
    • by location
    • by function
    • by origin and insertion
    • by # of origins
    • by shape
  51. fascia
    • CT associated with muscles
    • bind muscles together and stabilizes blood vessels and nerves as they enter/exit muscle
    • 2 types: superficial and deep
  52. superficial fascia
    subcutaneous skin
  53. deep fascia
    • dense irregular tissue that surrounds muscle, fasciles, and fiber
    • (epimysium, perimysium, endomysium)
  54. arrangements of fascicles
    • circular
    • fusiform: nearly parallel and tapered on ends
    • unipennate: short, attach to central tendon at an angle
    • bipennate: short, attach to central tendon at an angle on both sides
    • multipennate: short, attach to central tendon at an angle on many sides
    • parallel: attach to tendon top and bottom
  55. direct muscle attachment
    • epimysium attaches directly to periosteum of bone
    • ex: intercostals
  56. indirect muscle attachment
    • epimysium extends beyond muscle and turns into connective tissue cord which attaches muscle to other structures
    • cord can be tendon, aponeurosis, or tendon sheath
  57. tendon
    attaches muscle to bone
  58. aponeurosis
    broad flat tendon that attaches muscle to bone, skin, or other structure
  59. tendon sheath
    • CT structure that secretes synovial fluid
    • only found in a joint
  60. muscle contratction
    • must be stimulated by motor neuron
    • nerve impulse reaches axon terminal
    • Ach released from synaptic vessicles
    • Ach bridges synapse - allows impulse to cross synapse and reach sarcolemma
    • impulse moves down T tubules to sarcoplasmic reticulum
    • calcium ions dump into sarcoplasm
    • acetylcholinesterase enzyme (found on sarcolemma) is activated
    • calcium binds to troponin to form Ca-troponin complex
    • Ca-troponin complex attaches to tropomyosin to form tropomyosin blockade
    • tropomyosin tipped off active sites
    • ATP pivots cross bridges upward (power stroke)
    • cross bridges attach to exposed active sites
    • thin filaments slide over thick myosin
    • Z disk get closer together
    • I bands get smaller
    • A band unchanged
    • H zone almost completely disappears
  61. ATP
    • major energy source for muscle contraction
    • muscle cells only contain a small amount
    • body must replenish to keep muscles contracting
  62. creatinine phosphate
    • ADP converted to ATP for energy
    • provides small amount of ATP for initial activity
  63. glycogen
    • carbs stored in muscle fibers converted to ATP
    • source is limited but can keep muscles functioning temporarily
  64. cellular respiration
    • sugar, protein, amino acids converted to ATP
    • used for long term, extreme muscle activity
  65. types of muscle fibers
    • type 1: slow twitch - vascular, tend to resist fatigue
    • type 2: fast twitch - light in color (less vascular), fatigue easily
  66. isotonic
    • muscle shortens and contracts
    • work is being done because there is movement
    • produces bulk and definition
  67. isometric
    • muscle fibers become less tense but don't shorten
    • no work being done
    • produces muscle tone
  68. oxygen debt
    • O2 supply to a muscle is reduced
    • muscle stops contracting
    • feel burning and cramping sensation
    • muscle will stay cramped until O2 supply restored
  69. fatigue
    muscle cannot maintain strength of its contraction due to decreased O2 and decreased ATP
  70. twitch
    pathological response of a single muscle cell to a stimulus that is not strong enough to cause a contraction
  71. tetanus
    smooth sustained muscle contraction
  72. threshold
    stimulus that is strong enough to cause a muscle to contract
  73. subthreshold
    • weak stimulus
    • muscle can't contract
  74. muscle tone
    smooth sustained partial contraction
  75. all or none
    if a muscle cell contracts, it always contracts completely or not at all
  76. summation
    when a muscle receives rapid stimulation from several neurons, the strength of contraction increases
Card Set
A&P Chapter 10/11 - Muscles
A&P Chapter 10/11 - Muscles