Point 1 Intro Pathway Deficits Clinical Note Summary Overview Problems Contents  Anatomy

Corticospinal axons in the pyramids cross at the most caudal pole of the pyramids in the PYRAMIDAL DECUSSATION. These crossing fibers enter the lateral funiculus of the spinal cord where they are called the LATERAL CORTICOSPINAL TRACT ("corticospinal" is not good enough, you have to call them lateral corticospinal!). Lateral corticospinal tract axons exit the tract to terminate upon neurons in the spinal cord gray matter along its entire length. Some of the spinal cord neurons that receive direct input from lateral corticospinal fibers send axons into the ventral root to innervate striated muscles that move the arms and legs. In such instances only two neurons and one synapse (monosynaptic) are involved. Lateral corticospinal tract axons also end upon spinal cord neurons that do not directly innervate muscle, but instead synapse upon lower motor neurons. Such cells are called interneurons. A pathway involving a lateral corticospinal axon, an interneuron and a lower motor neuron is disynaptic.