Alpha Motor Neuron - Location

Location

Alpha motor neurons innervating the head and neck are found in the brainstem; the remaining α-MNs innervate the rest of the body and are found in the spinal cord. There are more α-MNs in the spinal cord than in the brainstem, as the number of α-MNs is directly proportional to the amount of fine motor control in that muscle. For example, the muscles of a single finger have more α-MNs per fiber, and more α-MNs in total, than the muscles of the quadriceps, which allows for finer control of the force a finger applies.

In general, α-MNs on one side of the brainstem or spinal cord innervate muscles on that same side of body. An exception is the trochlear nucleus in the brainstem, which innervates the superior oblique muscle of the eye on the opposite side of the face.