Final answer:
Axons from the 4 areas of SI cortex descend via the corticobulbar and corticospinal tracts for voluntary muscle movement, with corticobulbar being ipsilateral and corticospinal being largely contralateral.
Step-by-step explanation:
After traveling from the 4 areas of SI cortex, axons follow two descending pathways to control voluntary muscle movement. The two pathways are the corticobulbar tract and the corticospinal tract. The corticobulbar tract axons remain ipsilateral, influencing motor functions on the same side of the body, by synapsing with motor neurons in the brain stem. The corticospinal tract, on the other hand, features axons that are largely contralateral, crossing the midline in the brain stem or the spinal cord to control muscles on the opposite side of the body.