Muscular System

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Muscular System
2013-01-13 17:16:00
muscle anatomy

Anatomy and Physiology: Muscle Tissue
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  1. 3 Types of Muscle
    • skeletal
    • smooth
    • cardiac
  2. epimysium
    external dense envelope of connective tissue surrounding each muscle
  3. Perimysium
    partitions muscle into bundles of muscle cells
  4. fascicles
    individual bunches of muscle cells
  5. endomysium
    surrounds individual muscle cells
  6. Muscle Cells
    • develop from the mesoderm and will contain more than one nucleus
    • as the cell matures, striations appear
    • once adulthood is reached, muscle cells stop multiplying, although cells can become larger through exercise
    • in the elderly, muscle may atrophy(waste away) and be replaced by muscle tissue
    • damaged muscles may be replaced by precursor cells called satellite cells
    • muscle fibers consist of myofibrils containing myofilaments
    • myofilaments are thin proteins (actin) or thick proteins (myosin) and gives muscle its striated appearance
  7. Sarcomere
    repeating functional unit of each muscle fiver capable of contraction
  8. Neuromuscular Junction
    • (motor end plate)
    • between muscle fiver and neuron
  9. myoneural cells
    space between a neuron and a muscle fiber
  10. Manipulation of Continuous Action, Strength, and Control
    • 1. muscular contraction is dependent upon the number of motor units which are activated. Muscles requiring high precision containing more motor units effecting few cells
    • 2. for a sustained contraction, muscle fivers need to be stimulated several times; this is called tetanic contraction or tetany
  11. Energy for Muscle Fibers
    • comes from ATP
    • energy from ATY is converted into mechanical motion
    • resting muscle fibers rely on fatty acid breakdown
    • during active work, muscles rely on glucose breakdown doing aerobic respiration
    • the energy from the terminal phosphate group is often stored as creatine phosphate
  12. Anaerobic Respiration
    a muscle may go into anaerobic respiration when there is not enough when there is not enough oxygen, but this is less efficient. this requires large stores of glycogen which is converted to lactic acid and builds up leading to fatigue and cramps
  13. Function of Myoglobin
    • transfer of O2 from hemoglobin of RBCs to muscle fibers (myoglobin is not affected by decreasing pH levels due to lactic acid)
    • can hold small amounts of O2 for metabolism
  14. Sliding Filament Process
    this Actin slides among the thick myosin forming and breaking cross bridges, causing muscle contractions
  15. Rigor Mortis
    when ATP breaks down and is not replenished, the binding of cross bridges can not be released and the muscle becomes stiff
  16. Isotonic
    muscle contraction in which length, but not tension, of muscle changes (ex. weight lifting)
  17. Isometric
    contraction that produces no change in length, but tension increases
  18. Muscle Tone
    state of continuous contraction
  19. Atrophy
    • opposite of hypertrophy, when a muscle falls into disuse (ex. having a cast)
    • denervation may cause atrophy, muscle may eventually be replaced by adipose and fibrotic tissue
  20. Muscle Strength
    proportional to the cross-sectional area of the muscle
  21. Muscle Power
    the amount of work done/unit of time. velocity and rate of contraction are important
  22. Muscle Endurance
    influenced by nutrition, high glycogen stores are needed, therefore a carbohydrate-rich diet is useful
  23. Regions where Smooth Muscle may be Found
    • digestive tract
    • glands
    • skin
    • walls of arteries and veins
    • iris and ciliary body of the eye
  24. Smooth Muscle
    • do not possess sarcomeres, have a single nucleus
    • gaps between smooth muscle cells are gap junctions or nexuses, allows inpulse to pass form cell to cell without nerves
    • multiunit smooth muscles are innervated
    • rarely respire anaerobically; adapted to squeeze and shorten but respond slowly to stimuli
  25. Number of Muscles in the Human Body
    approximately 600
  26. Muscle arrangement
    muscles are arranged so that the pull of one muscle is counteracted by the pull of another or antagonistic muscle
  27. Origin
    • less-movable point of attachment
    • points of anchorage
  28. Insertion
    more-movable point of attachment
  29. Bellies
    a muscle shape, others include sphincter, rectangular, triangular, etc
  30. tone
    state of contraction, the abdominal muscles are almost always in some state of contraction
  31. synergists
    muscles responsible for joint fixation and stabilization, acts with prime movers
  32. Prime Movers
    muscles responsible for specific movements