Which of the following is NOT a distal motor nucleus of the brainstem?

Which of the following is NOT a distal motor nucleus of the brainstem?

• A. Trigeminal motor nucleus
• B. Facial motor nucleus
• C. Nucleus ambiguus
• D. Dorsal motor nucleus

Answer: (D)

Distinguish between motor nuclei that control skeletal muscles and those that provide autonomic (visceral) output. The nuclei that innervate skeletal muscles come from general somatic efferent (GSE) and special visceral efferent/branchial motor (SVE) pathways, including the trigeminal motor nucleus (muscles of mastication), the facial motor nucleus (muscles of facial expression), and the nucleus ambiguus (muscles of the pharynx and larynx via the glossopharyngeal, vagus, and accessory nerves). The dorsal motor nucleus, on the other hand, is a visceral motor (GVE) nucleus. It sends preganglionic parasympathetic fibers to autonomic targets in the thorax and abdomen, not to skeletal muscles. So it isn’t considered a distal motor nucleus of the brainstem in the sense of innervating skeletal muscle.

Distinguish between motor nuclei that control skeletal muscles and those that provide autonomic (visceral) output. The nuclei that innervate skeletal muscles come from general somatic efferent (GSE) and special visceral efferent/branchial motor (SVE) pathways, including the trigeminal motor nucleus (muscles of mastication), the facial motor nucleus (muscles of facial expression), and the nucleus ambiguus (muscles of the pharynx and larynx via the glossopharyngeal, vagus, and accessory nerves).

The dorsal motor nucleus, on the other hand, is a visceral motor (GVE) nucleus. It sends preganglionic parasympathetic fibers to autonomic targets in the thorax and abdomen, not to skeletal muscles. So it isn’t considered a distal motor nucleus of the brainstem in the sense of innervating skeletal muscle.