Gamma motor neurons perform which function?

• A. Move
• B. Sensitize spindles
• C. Innervate extrafusal fibers
• D. Regulate blood flow

Answer: (B)

The function being tested is how gamma motor neurons tune the muscle’s sensing system. They innervate the intrafusal fibers inside the muscle spindle, shortening them to maintain tension on the spindle and keep its sensory endings responsive to stretch even when the muscle itself is contracting. This keeps the spindle’s feedback accurate, helping the nervous system gauge length and rate of change in length during movement. Movement and force production, on the other hand, come from alpha motor neurons that innervate the extrafusal muscle fibers. Gamma neurons don’t directly cause contraction or regulate blood flow, so their main role is to sensitize (tune) the spindle.