A lower motor neuron that innervates only intrafusal muscle fibers. Unlike the alpha motor neurons, gamma motor neurons do not directly adjust the lengthening or shortening of muscles but function in adjusting the sensitivity of muscle spindles and in keeping muscle spindles taut, thereby allowing the continued firing of alpha neurons. [ WikipediaVersion:Gamma_motor_neuron&oldid=906640465 DOI:10.1093/acprof:oso/9780195159561.001.1 ]