gamma efferent fiber [Gk, gamma + L, efferre, to carry out, fibra, fiber] , any of the motor nerve fibers that transmit impulses from the central nervous system to the intrafusal fibers of the muscle spindle. The gamma efferent fibers are responsible for deep tendon reflexes, spasticity, and rigidity, but not for the degree of contractile response. They function in regulating the sensitivity of the spindle and the total tension of the muscle.
