Vagus Nerve

The vagus nerve ( /ˈveɪɡəs/ VAY-gəs), also called pneumogastric nerve or cranial nerve X, is the tenth of twelve (excluding CN0) paired cranial nerves. Upon leaving the medulla between the medullary pyramid and the inferior cerebellar peduncle, it extends through the jugular foramen, then passes into the carotid sheath between the internal carotid artery and the internal jugular vein down below the head, to the neck, chest and abdomen, where it contributes to the innervation of the viscera. Besides output to the various organs in the body, the vagus nerve conveys sensory information about the state of the body's organs to the central nervous system. 80-90% of the nerve fibers in the vagus nerve are afferent (sensory) nerves communicating the state of the viscera to the brain.

The medieval Latin word vagus means literally "wandering" (the words vagrant, vagabond, and vague come from the same root). Sometimes the branches are spoken of in the plural and are thus called vagi (/ˈveɪdʒaɪ/, US dict: vā′·jī). The vagus is also called the pneumogastric nerve since it innervates both the lungs and the stomach.

The motor division of the vagus nerve is derived from the basal plate of the embryonic medulla oblongata, while the sensory division originates from the cranial neural crest.

The vagus nerve includes axons which emerge from or converge onto three nuclei of the medulla:

1. The Dorsal nucleus of vagus nerve - which sends parasympathetic output to the viscera, especially the intestines
2. The Nucleus ambiguus - which sends parasympathetic output to the heart (slowing it down) and
3. The Solitary nucleus - which receives afferent taste information and primary afferents from visceral organs