The vagus nerve is either one of two cranial nerves which are extremely long, extending from the brain stem all the way to the viscera. The vagus nerves carry a wide assortment of signals to and from the brain, and they are responsible for a number of instinctive responses in the body. You may also hear the vagus nerve called Cranial Nerve X, as it is the 10th cranial nerve, or the Wandering Nerve. A great deal of research has been carried out on the vagus nerve, as it is a rather fascinating cranial nerve.
Vagus is Latin for “wandering,” and it is an accurate description of this nerve, which emerges at the back of the skull and meanders in a leisurely way through the abdomen, with a number of branching nerves coming into contact with the heart, lungs, voicebox, stomach, and ears, among other body parts. The vagus nerve carries incoming information from the nervous system to the brain, providing information about what the body is doing, and it also transmits outgoing information which governs a range of reflex responses.
The vagus nerve helps to regulate the heart beat, control muscle movement, keep a person breathing, and to transmit a variety of chemicals through the body. It is also responsible for keeping the digestive tract in working order, contracting the muscles of the stomach and intestines to help process food, and sending back information about what is being digested and what the body is getting out of it.
When the vagus nerve is stimulated, the response is often a reduction in heart-rate or breathing. In some cases, excessive stimulation can cause someone to have what is known as a vaso-vagal response, appearing to fall into a faint or coma because his or her heart rate and blood pressure drop so much. Selective stimulation of this nerve is also used in some medical treatment; vagus stimulation appears to benefit people who suffer from depression, for example, and it is also sometimes used to treat epilepsy.
Most of the time, you don't notice the actions of the right and left vagus nerves, but you probably would notice if this nerve ceased to function as a result of disease or trauma, because the vagus nerve is one of the many vital nerves which keeps your body in working order. Without the functions of the vagus nerve, you would find it difficult to speak, breathe, or eat, and your heartbeat would become extremely irregular.