One aspect of the study of neurology is identifying the individual nerves that work to carry sensory information from various parts of the body to the brain. The nervus vagus is an important pathway in the nervous system because it carries signals from several areas of the body, including the lungs, esophagus, stomach, larynx (voice box), pharynx, lungs, heart and a large part of the digestive system. Literally translated, "vagus" means "wandering" in Latin. The most complex as well as the longest of the nerves descending from the brain, the vagus nerve earns its name by wandering through a large area of the body to serve this wide range of organs.
A cranial nerve, the nervus vagus finds its origins in the brain, in rootlets from the lateral side of the medulla oblongata. Passing through the jugular foramen, an opening in the skull, it continues between the carotid artery and the jugular vein in the carotid sheath. From there, it spreads and branches throughout the body, giving rise to several branches along the way. Body functions that depend on the nervus vagus include peristalsis — wavelike contractions — in the gastrointestinal tract, sweating and even movement of the mouth that enables speech.
Also known as the tenth cranial nerve or the pneumogastric nerve, the nervus vagus carries signals to these areas of the body from the brain and delivers messages back to the brain. Among other functions, this path can send signals that will lower the heart rate when necessary by interacting with the sinoatrial node. More than 80 percent of the nerve fibers in this pathway carry sensory information so the brain can interpret the overall state of the lungs, heart and viscera. The rest of the nerve fibers are motor fibers that trigger movement or action in the body. Because the nervus vagus carries both sensory and motor fibers, it is considered a mixed nerve.
Stimulation of the nervus vagus using a device similar to a heart pacemaker is sometimes used to treat epileptic seizures and some forms of depression that do not respond to medications. This pathway also can be stimulated through specific movements or muscle contractions. These types of stimulation are occasionally recommended for patients who suffer from certain kinds of heart arrhythmia. Blocking the action of the nervus vagus through similar manipulations or even cutting it in a procedure called a vogotomy is sometimes used in conjunction with bariatric surgery to treat morbid obesity.