Most fibers of the parasympathetic nervous system travel in the __ nerv Select one: A. trigeminal B. facial C. splanchnic D. vagus
The Correct Answer and Explanation is:
The correct answer is D. vagus.
The vagus nerve, also known as cranial nerve X, is the primary pathway through which parasympathetic fibers travel throughout the body. It is the most extensive cranial nerve, originating in the medulla oblongata and extending down into the thorax and abdomen. About seventy-five percent of all parasympathetic fibers in the body run through this single nerve.
The parasympathetic nervous system is part of the autonomic nervous system and functions to conserve energy and restore the body to a state of calm. It is responsible for activities such as reducing heart rate, promoting digestion, increasing glandular activity, and facilitating rest.
The vagus nerve contributes significantly to these functions by innervating major visceral organs. It sends efferent signals to structures like the heart, lungs, esophagus, stomach, pancreas, kidneys, intestines, and liver. It also carries afferent sensory information from these organs back to the brain, helping regulate homeostatic functions like blood pressure and gastrointestinal motility.
In contrast, the other choices serve different roles:
- The trigeminal nerve (CN V) is mainly involved in facial sensation and motor control of mastication.
- The facial nerve (CN VII) carries some parasympathetic fibers, but its reach is largely confined to salivary and lacrimal glands.
- The splanchnic nerves are primarily associated with the sympathetic nervous system, although some carry visceral afferent fibers.
The vagus nerve’s crucial involvement in parasympathetic control makes it a key player in maintaining internal equilibrium. Its clinical relevance extends to areas such as vagus nerve stimulation for epilepsy and depression, and its dysfunction can impact multiple organ systems.
