The Vagus nerve is tenth of twelve cranial nerves and the only nerve that starts in the brainstem (somewhere in the medulla oblongata) and extends way down past the head, all the way down to the abdomen.

It was for this reason that it was so named, for "the wanderer" (the words "vagrant" and "vagabond" come from the same Latin word).

This nerve supplies motor and sensory parasympathetic fibres to pretty much everything from the neck down to the first third of the transverse colon. This nerve is responsible, amongst other things, such varied tasks as moderating the heart rate, gastrointestinal peristalsis, sweating and speech (via the recurrent laryngeal nerve). I cannot overstate how important this is.

As if those rather important functions weren't enough, the vagus nerve also controls a few skeletal muscles, namely:

The vagus is responsible for quite a few muscle movements in the mouth and also is vitally important for speech and in keeping the larynx open for breathing.

It also receives some sensation from the outer ear and part of the meninges.

Arguably the single most important nerve in the body.

Cranial nerves

/msg me for errors/omissions/comments. thanks

To slightly supplement alex.tan's wicked-cool neuroanatomy node, the reason that this nerve is so important that it is mostly in control of all of the fun fun things that you do with your mouth, like speaking, swallowing, vomiting, coughing and salivating.

In addition, this nerve provides critical visceral feedback information to the brain. For example, without the vagus nerve, your body wouldn't be able to measure its own blood pressure (there are pressure-sensitive neural mechanisms in the heart) and wouldn't be able to tell how full or empty the various parts of the GI tract are.

One astounding new treatment for clinical depression involves the implantation of a specialized cardiac pacemaker designed to intermittently electrically stimulate these sensory fibers of the vagus nerve. The theory is that depression may have a lot to do with how the actions of stress hormones in the body (e.g. on the viscera) feedback to the brain; the visceral organs are all targets for the major stress hormones, and it is thought that a lack of feedback signal from these organs via the vagus nerve might be responsible for some of the physiological and hormonal changes typical to depression. The theory behind the pacemaker treatment, (currently in clinical trials reserved for only those that don't respond to anti-depressants,) is that by stimulating the sensory portion of the vagal nerve, you create artificial feedback which helps adjust the patients hormonal response to more normal, pre-depression functioning. The treatment is surprisingly successful, considering that it is essentially a very clever, very specific, very subtle form of electro-convulsive therapy.

So, next time you lean back in your chair, feeling the happiness that is a sated, happy stomach full of yummy food - or feel your guts twist and churn as you watch your latest WU plunge into negative rep -- thank your hard working vagus nerve.

Vagus Nerve Stimulator

The vagus nerve stimulator (VNS), manufactured by Cyberonics, is a new and promising alternative for medically refractory seizures, treatment-resistant depression and in one isolated case, the "hiccups".  Medically refractory seizures are those in which patients have tried two or more medications and are still not satisfied with seizure control, side effects, and the quality of their life.  Treatment-resistant depression is where the patient has exhausted all alternatives, including psychotherapy, multiple trials of medications, and electroconvulsive therapy (ECT).

Similar to a stopwatch-sized pacemaker, a VNS is a small device implanted under the skin near the collarbone, or close to the armpit.  Two tiny wires from the device wrap around the vagus nerve on the left side of  the neck.  While this may sound serious, the procedure involves two small incisions, takes about an hour, and is often done on an outpatient basis.  Once implanted in the body, the battery-powered device can be programmed from outside the body by a doctor.  A handheld magnet can also be used to turn the device on such as in the case of a seizure patient feeling a seizure about to start.  The doctor programs the device to produce weak electrical signals that travel along the vagus nerve to your brain at regular intervals.  These signals help prevent the electrical bursts in the brain that cause seizures.  For acute, chronic, treatment-resistant depression VNS is something of a mystery to scientists.  It is believed that electrical stimulation alters the chemical neurotransmitters that carry messages across the gaps, called synapses, between nerve cells.

The VNS is considered safe.  It has been approved by the U.S. Food and Drug Administration (FDA), and this type of treatment is an area of ongoing research.

Mild side effects occur in some people when the device stimulates the nerve.  The most common side effects include coughing, throat pain, hoarseness or slight voice change, a prickling feeling on the skin, and shortness of breath.  In children, VNS has caused hyperactivity.  These side effects become less noticeable over time.  However, clinical studies show that VNS has resulted in an improvement in alertness, memory, plus more energy and a better mood.

In one isolated case,  a man in New Orleans, after suffering seven months of constant, bark-like hiccups has had the VNS device implanted in his chest and now has returned to his normal life as a 50 year old.  His speech is now a hoarse whisper which is one of the side effects of the treatment.  But, for the first time since November 2003, he can eat, sleep and no longer has to make himself gag to make the hiccups stop.  He can talk without a bark-like hiccup every three to four seconds.

In 2006, Cyberonics will invest aggressively in new studies to test the effectiveness of VNS on Alzheimer's disease, anxiety and headaches.






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