The Muscular System

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The Muscular System
2012-03-11 20:26:36
Muscular system

Skeletal, Cardiac and Smooth muscle
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  1. Functions of the Muscle
    • Movement
    • Stability
    • Control of body openings and passages
    • heat production
    • glycemic control
  2. Properties of Muscle
    • Excitability (responsiveness)
    • Conductivity
    • contractility
    • extensibility
    • elasticity
  3. Skeletal Muscle
    • voluntary
    • striated
    • produces 85% heat
    • usually connect to 1+bones
  4. Cardiac Muscle
    • involuntary
    • striated
    • found in heart
    • very rich in myoglobin, glycogen and big mitochondria= very resistant to fatigue
    • repair of damaged cardiac muscle primarily by fibrosis
  5. Smooth Muscle
    • involuntary
    • no striations
    • found in walls of viscera and blood vessesl iris of eye, piloerectors of hair follicles
  6. myofibers
    • cells of skeletal muscle
    • surrounded by endomysium, bundled by perimysium, put together by epimysium, covered by fascia
    • multiple nuclei, adjacent to sarcolemma
  7. cardiocytes
    • cells of cardiac muscles
    • aka myocytes
    • usually one nucleus near middle of cell
  8. myocytes
    • can refer to cells of either cardiac or smooth muscle
    • in smooth muscle, contain only one nuclei
    • z discs are absent
  9. prime mover
    • muslce that produces most of the force during a particular joint action
    • aka agonist
  10. synergist
    • muscle that aids the prime mover
    • guide for prime mover
  11. antagonist
    • opposes prime mover
    • makes antagonistic pair with prime mover*
  12. fixator
    muscle that prevents a bone from moving
  13. intrinsic v extrinsic
    • intrinsic muscle has origin and insertion contained within a particular region
    • extrinsic doesnt, ex. muscles that move fingers
  14. First class lever
    fulcrum in the middle like seesaw (EFR)
  15. Second-class lever
    Resistance in the middle (FRE)
  16. Third-class lever
    effort applied between the fulcrum and resistance (FER)
  17. Sarcolemma
    plasma membrane of muscle fiber cell
  18. Sarcoplasm
    • cytoplasm of myofiber
    • occupied by myofibrils and myoglobin
  19. Sarcoplasmic Reticulum
    smooth endoplasmic reticulum of myofibers
  20. Myofilaments
    • thick filaments
    • myosin
    • Thin filaments
    • actin-> tropomyosin-> troponin

    • Elastic Filaments
    • titin (anchor each thick filament to the z disc
  21. Contractin Proteins
    • myosin and actin
    • because they do work of shortening the muscle fiber
  22. regulatory proteins
    becuase they act like a swetich to determine when the fiber can contract and when it cannot
  23. Neuromuscular Junction
    Point of contact between nerve and muscle fiber
  24. Excitation 1
    • a nerve signal arrives at the synaptic knob
    • synaptic vesicles release ACh which diffuses xross synaptic cleft and binds to receptros on the sarcolemma of the muscle fiber, opens ion gates in sarcolemma and sodium and potassium movements throught hte membrane that electrically excite the msucle fiber
    • self-propagating wave of excitation spreads down the length of the fiber and into the T tubules
  25. Excitation- Contraction Coupling 2
    • electrical events in T tubule lead to the opening of calcium gates in teh sarcoplasmic reticulum, sr releases calcium ions into the cytosol
    • calcium ions bind to troponin molecules in the myofilaments
    • myosin has been "waiting" in flexed position like elbow with atp bound to head, reaction straightens myosin head into extended "cocked"position
  26. Contraction 3
    • myosin forms a link, or cross-bridge, with one of the active sites of actin, and releases the ADP and P
    • mysoin flexes and tugs on thin filament (power stroke), myosin binds new ATP, lets go of thin filament and reckocks (recovery stroke)
  27. Relaxation 4
    • motor neuron stops firing and releasing ACh, muscle fiber no longer electrically excited
    • sarcoplasmic reticulum reabsorbs calcium ions and stores them til next time muscle stimulated, troponin blocks active sites and prevents myosin-actin cross-bridges fro froming, muscle can no llonger maintain tension, relaxes
  28. atrophy
    when muscle shrinks
  29. denervation atrophy
    spinal cord injuries or other injuries that sever nerve from muscle and cause muscle to shrink
  30. disuse atrophy
    lack of excercise
  31. senscence atrophy
    from aging
  32. myopathies
    diseases of muscular tissue
  33. muscular dystrophy
    collective term for several hereditary diseases in which skeletal muscles degenerate, lose strength, and are gradually replaced by fat and scar tissue which impede blood circulation and accelerates muscle degeneration
  34. Myasthenia gravis (MG)
    • most prevalent in women from 20-40
    • autoimmune disease in which antibodies attack neuromuscular junctions and trigger destruction of ACh receptors
    • fibers become lesss and less sensitive to ACh