Structure and Function of the Vagus Nerve - Vagus nerve extends through the jugular foramen and passes into the carotid sheath - Innervates the viscera - Sensory fibers originate from neurons of the nodose ganglion - Motor fibers come from neurons of the dorsal motor nucleus of the vagus and the nucleus ambiguus - Supplies motor parasympathetic fibers to organs - Controls skeletal muscles in the mouth - Responsible for heart rate, gastrointestinal peristalsis, and sweating - Innervates the inner portion of the outer ear and part of the meninges - Regulates inflammation in the body

Cardiac and Urogenital Effects of the Vagus Nerve - Parasympathetic innervation of the heart is controlled by the vagus nerve - Vagal and spinal ganglionic nerves lower the heart rate - Right vagus branch innervates the sinoatrial node - Hyperstimulation of parasympathetic influence promotes bradyarrhythmias - Left vagal branch predisposes the heart to conduction block at the atrioventricular node - Excessive activation of the vagal nerve during emotional stress can cause vasovagal syncope - Vasovagal syncope affects young children and women more than other groups - Can lead to temporary loss of bladder control under extreme fear - Women with complete spinal cord injury can experience orgasms through the vagus nerve - Insulin signaling activates ATP-sensitive potassium channels and decreases glucose production by the liver

Clinical Significance of the Vagus Nerve - Anticholinergic drugs inhibit the action of the vagus nerve on the heart and other organs - Drugs that inhibit muscarinic receptors increase heart rate and treat bradycardia - Vasovagal syncope can cause a sudden drop in cardiac output and cerebral hypoperfusion - Vagus nerve stimulation can be used to treat certain neurological disorders - Vagus nerve plays a role in the regulation of inflammation and satiation

Stimulation of the Vagus Nerve - Vagus nerve stimulation (VNS) therapy has been used to control seizures in epilepsy patients and treat drug-resistant clinical depression - Noninvasive VNS devices that stimulate the vagus nerve are available - VNS can also be achieved through vagal maneuvers such as holding the breath, dipping the face in cold water, coughing, humming or singing, or tensing the stomach muscles - Patients with certain illnesses may be trained to perform vagal maneuvers - Vagus nerve blocking (VBLOC) therapy is similar to VNS but used only during the day and has shown promising results in weight loss

Vagus Nerve Pathology and Other Health Conditions - Vagotomy, a now obsolete therapy, was performed for peptic ulcer disease but has been superseded by oral medications - Vagotomy is being researched as a less invasive alternative weight-loss procedure to gastric bypass surgery - Vagus nerve dysfunction can cause various symptoms throughout the body due to its control over the autonomic nervous system - Vagus nerve involvement in cluster headaches - Vagus nerve involvement in Parkinson's disease - Vagus nerve cough reflex and chronic cough - Potential role of the vagus nerve in pernicious anemia