The vagus nerve is a long cranial nerve that stretches from the brainstem to the colon and is involved in an extensive list of functions. In this video, I summarize the main functions of the vagus nerve, talk about the nuclei associated with the nerve, and discuss some of the symptoms that can appear when the vagus nerve is damaged.
The vagus nerve is an extremely long nerve that travels from the brainstem to the colon and has a long list of functions. It carries sensory information about pain, touch, and temperature from the throat, parts of the inner and outer ear, and the meninges near the back of the head. It plays a very minor role in taste. It also receives sensory information from internal organs in the neck, chest and abdomen like the esophagus, heart, and digestive tract. And it carries sensory information from both baroreceptors in the aorta that detect changes in blood pressure, and chemoreceptors in the aorta that sense oxygen levels in the blood. The vagus nerve controls the movement of a number of muscles in the pharynx, soft palate, and larynx (as well as one muscle in the tongue) to play a critical role in the control of speaking and swallowing. It is also the main parasympathetic nerve of the body, providing parasympathetic innervation to organs throughout the neck, thorax, and abdomen, contributing to a variety of functions such as slowing of the heart rate.
There are several nuclei in the medulla associated with the vagus nerve and the different types of information it carries. Information about touch, pain, and temperature travels to the spinal trigeminal nucleus. Sensory information from internal organs, or visceral sensory information, travels to the solitary nucleus. Motor signals originate in the nucleus ambiguus. Parasympathetic fibers originate primarily in the dorsal vagal motor nucleus, while some parasympathetic fibers that travel to the heart begin in the nucleus ambiguus.
Symptoms of vagus nerve damage may include hoarseness of the voice, difficulty swallowing, and a deficient gag reflex. The uvula may deviate away from the side where the damage has occurred. Because the nerve supplies a number of organs, however, damage can result in many other symptoms as well, like abnormalities in heart rate or gastrointestinal problems.
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Wilson-Pauwels L, Akesson EJ, Stewart PA, Spacey SD. Cranial Nerves in Health and Disease. 2nd ed. London: BC Decker, Inc; 2002.