KEY CONCEPTS

This is a lateral view of the brain and upper spinal cord, indicating the pathway of the corticospinal tract from the primary motor  cortex via the spinal cord to the periphery. Note: the tracts are deep within the brain, not on the surface as shown here.

The corticospinal pathway:

• Carries voluntary motor commands.
• Controls spinal reflexes.
• Has each axon begining in the motor cortex and terminating in the spinal cord at or near its target lower motor neuron.
• Has most (~85%) of its axons crossing sides in the ventral medulla (decussation of the pyramids) to create the lateral cortico-spinal tract.
• Has a few (~15%) of its cortico-spinal axons (forming the anterior/ventral cortico-spinal tract) that stay on the same side but eventually cross in the spinal cord near their termination (not shown in this picture).