Final answer:
The corticospinal tract connects the motor cortex with the spinal cord, controlling voluntary muscle movements. Axons from the motor cortex largely cross over to the opposite side in the corticospinal tract, while the anterior corticospinal tract can be bilateral to coordinate trunk movement.
Step-by-step explanation:
The corticospinal tract (CST) is a critical neural pathway that connects the motor cortex in the brain to the spinal cord, playing a vital role in controlling voluntary muscle movements. The axons from the motor cortex project onto the upper motor neurons either within the cranial motor nuclei (forming the corticobulbar tract) or within the ventral horn of the spinal cord (forming the corticospinal tract).
The majority of CST axons are contralateral, crossing over to the opposite side at the medullary-spinal border in an area known as the pyramidal decussation. This means that the right side of the brain controls muscles on the left side of the body and vice versa. A smaller portion of these fibers, part of the anterior corticospinal tract, do not cross over immediately but may do so at the spinal level or remain ipsilateral to coordinate trunk movement in a bilateral fashion.