Gamma motor neurons (
γ motor neurons), also called
gamma motoneurons, are a type of
lower motor neuron that take part in the process of
muscle contraction, and represent about 30% of fibers going to the muscle. Like
alpha motor neurons, their cell bodies are located in the
anterior horn of the spinal cord. They receive input from the bulboreticular facilitatory region of the
pons in the
brainstem. Their axons are smaller than alpha motor neurons, with a diameter of only 5 μm. Unlike the alpha motor neurons, gamma motor neurons do not directly adjust the lengthening or shortening of muscles. However, their role is important in keeping
muscle spindles taut, thereby allowing the firing of alpha neurons to continue discharging, leading to muscle contraction. These neurons also play a role in adjusting the sensitivity of
muscle spindles.