Point 5 Intro Pathway Deficits Summary Caveat Problems Contents Anatomy

The ventral horn contains some of the largest cells in the central nervous system. The large neurons directly innervate muscles. We need to think about what happens when there is a lesion that damages these large ventral horn motor neurons. When such damage occurs the motor neurons die, their axons in the ventral root die and the muscles that they innervate eventually die. The muscle dies because it has lost its source of nourishment or trophic source (trophic = nourishment). When the muscle dies it ATROPHIES or shrinks-up. (atrophy = wasting). Atrophy occurs only when the cells that DIRECTLY innervate the muscle die, also as the lower motor neurons die, the muscles they innervate sometimes twitch. These twitches, as seen by the naked eye, are called fasciculations. CELLS THAT DIRECTLY INNERVATE MUSCLES ARE CALLED LOWER MOTOR NEURONS (LMNs)