Final answer:
The correct answer is E) brainstem, where the axons of the corticospinal tract cross over at the pyramidal decussation in the medulla.
Step-by-step explanation:
The pyramidal tract neurons, specifically those of the corticospinal tract, are crucial for voluntary motor control. Lower motor neurons are activated by axons from Betz cells located in the primary motor cortex. These axons primarily follow two pathways, the corticobulbar tract and the corticospinal tract.
Notably, axons of the corticospinal tract cross to the contralateral side, meaning the opposite side of the body, in the brainstem region. This crossing over occurs at a specific point in the medulla known as the pyramidal decussation, defining the transition from brain to spinal cord.
Therefore, the correct answer to the question 'Pyramidal tract neurons cross to the opposite side of the body in what region?' is E) brainstem.