Question

The major output neurons of the cortex, including those that comprise the corticospinal tract, are recognizable by their ________.

a. Restricted localization to layer 4 of the cortex.

b. Large glutamatergic cell bodies in cortical layer 5

c. Short axons that do not project outside of the cortex

d. Production of GABA

e. Primarily ipsilateral projections to the spinal cord

Answer 1

a. Restricted localization to layer 4 of the cortex.

Most of the corticospinal tract fibers originate from the precentral gyrus layer 4 of the cortex which is responsible for the control of the motor nerves. So the output of neurons comprising corticospinal tract is restricted to layer 4 of the cortex.

The output neurons comprising dorsal spinocerebellar tract neurons are inhibited by the production GABA. Therefore corticospinal tract has inhibitory control on interneuronal system.

The corticospinal tract axons are contralateral, not ipsilateral. The axons of the corticospinal tract project across the midline of the spinal cord or brain stem and synapse on the opposite side of the body.