Intrafusal Muscle Fibers but Not Extrafusal Fibers

Question

Intrafusal muscle fibers but not extrafusal fibers:
A)Receive only sensory innervation.
B)Are innervated by only one motor neuron.
C)Contain an equatorial region with little to no contractile protein.
D)Run the length of the muscle.

Accepted Answer

Intrafusal muscle fibers, unlike extrafusal fibers, have a central region (equatorial region) that is characterized by a lack of or significantly reduced amount of contractile proteins. This region is primarily involved in sensory detection, particularly in the stretch reflex mechanism, rather than contraction.