True about Nuclear bag fibers

Discussion in 'AIIMS Nov 2013' started by samuel, Nov 27, 2014.

  1. samuel

    samuel New Member

    True about Nuclear bag fibers
    a) Sense dynamic length of muscle
    b) Involved in reciprocal innervation
    c) Alpha motor neuron stimulation
    d) Senses muscle tension

    Answer: Sense dynamic length of muscle

    Explanation:
    Intrafusal fibers are a second category of
    muscle fibers found specifically within muscle
    spindles.
    Intrafusal fibers are classified as nuclear bag
    fibers containing many nuclei in a dilated
    central area and nuclear chain fibers lacking
    definitive bag. There are two subtypes of the
    nuclear bag fibers, dynamic and static.
    Two types of sensory (afferent) nerves
    innervate intrafusal fibers:
    Group Ia afferent nerves innervate both nuclear
    bag fibers and nuclear chain fibers, and
    transmit information regarding the rate of
    change in muscle length (Dynamic response).
    Group II afferent nerves mainly innervate
    nuclear chain fibers and do not innervate the
    dynamic nuclear bag fibers.
    The steady state activity of group Ia and II
    afferent provide information on steady state
    length of muscle (Static response)

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