Where are the motor nuclei located?

• A. Brainstem and spinal cord
• B. Cortex and cerebellum
• C. Spinal cord only
• D. Brainstem only

Answer: (A)

Motor nuclei are the cell bodies of the neurons that directly innervate skeletal muscles—the final pathway to muscle contraction. These cell bodies sit in two main locations: the cranial nerve nuclei in the brainstem, which control muscles of the face, head, and neck, and the ventral horns of the spinal cord, whose neurons project to trunk and limb muscles. So, the motor nuclei span both brainstem and spinal cord.

The other options miss part of this picture. The cortex and cerebellum are higher centers that plan and coordinate movement but do not contain the neurons that directly spur muscle fibers. If you chose spinal cord only, you’d be omitting the brainstem motor nuclei; if you chose brainstem only, you’d be missing the spinal cord motor nuclei.