Which nerve carries parasympathetic fibers to most thoracic and abdominal organs?

• A. Facial nerve
• B. Vagus nerve
• C. Glossopharyngeal nerve
• D. Hypoglossal nerve

Answer: (B)

The main idea is that parasympathetic control of the thoracic and much of the abdominal viscera comes from the vagus nerve. This cranial nerve provides the majority of parasympathetic outflow to the heart, lungs, esophagus, stomach, and much of the small and large intestine. Its preganglionic neurons reside in the brainstem (dorsal motor nucleus and, for some fibers, nucleus ambiguus), and these fibers reach intramural ganglia in the organs where they synapse with postganglionic neurons. From there, the signals slow the heart, promote bronchoconstriction, and stimulate digestive activities.

Other nerves carry parasympathetic fibers to more specific targets: the facial nerve mainly to lacrimal and some salivary glands; the glossopharyngeal nerve to the parotid gland; and the hypoglossal nerve is primarily a motor nerve to the tongue rather than autonomic. It’s also useful to note that sacral parasympathetic fibers (from pelvic splanchnic nerves) supply the remaining distal colon, rectum, bladder, and reproductive organs, but for most thoracic and upper abdominal organs the vagus is the primary pathway.