Motor supply to muscle spindle is through-
Ans. is 'c' i.e., Gamma Sensory innervation (afferent) of muscle spindle* Two types of sensory nerve fibers (afferent) originate from the intrafusal fibers : -1) Annulospiral (Primary) ending are wound around the central region of both nuclear bag fiber and nuclear chain fiber. These are Aa (or la) fibers.2) Flower-spray (Secondary) endings innervate the peripheral parts (ends) of nuclear chain fiber. These are Ab or (or II) fibers.Motor innervation (efferent) of muscle spindle* The peripheral part of both nuclear bag fiber and nuclear chain fiber are innervated by motor fibers which are Ag type also called y-motor neurons or fusimotor neuron or Lekcell efferents. g1 (dynamic g-fibers) innervate nuclear bag fiber and their terminals are called 'plate ending'. g2 (static - g - fibers) innervate nuclear chain fibers and their endings are called 'trail ending'. Ag fibers alter spindle sensitivity to stretch. y2 fibers alter the dynamic sensitivity, whereas g2 fibers alter the static sensitivity of stretch reflex. Neurons of Intrafusal fibers (spindles)Afferent (Sensory) neuronsEfferent (Motor) neurons* Aa (Type Ia)* Ab (Type II)* g-motor (Ag)
Alpha
Beta
Gamma
Delta
Nervous System