Muscle System

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  1. Over 700 muscles in the body
  2. Four basic properties
    • Excitability
    • Contractibilty
    • Extensibilty
    • Elasticity
  3. Ecitability - The ability to respond to stimulation
    Skeletal muscles normally respond to stimulation by the nervous system

    Cardiac and smooth muscles respond to both the nervous system and circulationg hormones
  4. Contractibility
    The ability to shorten and exert a pull
  5. Extensibility
  6. *Skeletal Muscle perform the following functions:
    • Produce Skeletal Movement
    • Maintain Posture and Body position
    • Support and protect soft tissues
    • Regulate entering and exiting of the body
    • Maintain body temperature
  7. Each muscle is a discrete organ composed of muscle tossue, blood vessels, nerve fibers, and connective tissue
  8. The 3 connective tissue sheaths are:
    Epimysium - dense irregular connective tissue that surrounds the entire muscle

    Perimysium - dense irregular connective tissue that surrounds the group of muscle fibers called, fasciles, vessels and nerves

    Endomysium - areolar connective tissue composed of reticular fibers surrounding each muscle fiber; extensive capillary network
  9. Sarcolemma
    The cell membrane of a muscle cell
  10. T-tubles
    projections of the sarcolemma into sarcoplasm
  11. Sarcoplasmic Reticulum
    surrounds each myofibril
  12. Myofibrils
    densely packed, rod like, contractile organelles within the cell; arranged in a repeating series of dark A bands and light I bands
  13. Mitochondria
    located between myofibrils
  14. Sarcomeres
    The smallest contractile unit of a muscle

    The region of a myofibril between two Z-Discs; repeat along entire length of Myofibirl

    Composed of Myofilaments - two types - (thick composed of myosin Dark band look; A band) (thin - they are located beteween the sarcomeres composed of actin; I band; Light band look)
  15. Thick filamments (myosin)
    extend the entire length of an A Band
  16. Thin Filamanet (actin)
    extend across the I band and partly into the A band
  17. Z-disc
    sheet of proteins that anchors the thin filaments and connects the filaments to one another.
  18. Calcium ions store in the cytoplasmic reticulum
  19. In the relaxed state, thick and thin filaments overlap only slightly
  20. Upon stimulation, myosin heads bind to actin and sliding begins
  21. Thin Filaments (actin) slide past the thick filaments (myosin)
  22. What happens at Contraction:
    • The H band and the I band get smaller
    • The Zone of overlaps get get larger
    • The Z-lines move closer together
    • The width of the A band remains constant throughout the contraction
    • The entire Sarcomere shortens
  23. Nerve Stimulus of Skeletal Muscle
    Skeletal muscles are stimulated by motor neurons of the somatic nervous system

    Axons of these neurons travel to the muscle, branching profusely as they enter

    each Axonal branch forms a neuromuscular junction with a single muscle fiber
  24. The neuromuscular junction(synapse) is formed between an axonal ending and a muscle fiber
  25. 3 components of Neuromuscular junction NMJ
    1. Axon terminal - synaptic vesicles w/ ACh (acetylcholine)

    2. Synaptoc Cleft - space between axon ending and muscle fiber

    3. Motor end plate (of a muscle fiber) - specific region on the sarcolemma that contains Acetylcholine receptors
  26. When the electro stimulation ends, the sacroplasmic reticulim will recapture the calcium ions and the contraction will end
  27. How does the elecrticla stimulation....
  28. Motor Unit
    A motor unit is a motor neuron and all the muscle fibers its supplies

    The number of muscle fibers per motor unit can vary from four to several hunderd

    • Eye = 1 neuron controls 2-4 fibers
    • Legs = 1 neuron can control 2000 fibers
  29. Muscle Tone
    Some of the motor units of muscles contract continuosly producing a resting tension in a skeletal muscle called muscle tone

    Resting muscle tone stabilizes the position of the bones and joints and provides ideal overlap for contraction
  30. Muscle Hypertrophy and Atrophy
    Exercise causes and increase/enlargement of a stimulated muscle called hypertrophy

    Disuse of a muscle results in the opposite, called Atrophy
  31. Types of Skeletal Muscle Fibers

    Fast fibers or White fibers are:
    • Large in Diameter
    • Large Glycogen
    • Anaerobic Metabolism:
    • *their mitochondria are unable to meet the demand
    • Fast powerful contractions
    • Fatigue easily
  32. Slow Fibers or Red fibers features:
    • are about half the diameter of fast fibers
    • Takes 3 times as long to contract after stimulation
    • Contain abundant mitochondria
    • Use aerobic metabolism
    • have a more extensive network of capillaries than do muscles dominated by the fast muscle fibers
    • extended contractions
  33. Intermediate Fibers
    have properties intermediate between those of fast fibers and slow fibers

    contract faster than slow fibers bu slower than fast fibers

    • Are very similiar to fast fibers except:
    • They have more mitochondria
    • A slightly increased capillary supply
    • A greater resistance to fatigue
Card Set:
Muscle System
2012-02-28 04:33:38

Skeletal Muscle
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