Cranial Nerve #10: Vagus Nerve

Description and Physiology

The vagus nerve is a mixed nerve with both sensory and motor functions.  It is the longest of the cranial nerves as it extends from the brain stem, through the muscles of the mouth, neck, thorax, lungs, and abdomen. The vagus nerve conveys sensory information about the state of the body’s organs to the nervous system.  It also receives a special sense of taste sent from the epiglottis.  The posterior muscle of the tongue, the palatoglossus, is controlled by the vagus nerve.  The vagus nerve helps to regulate the heartbeat, control muscle movement, keep a person breathing, and to transmit a variety of chemicals through the body.  The vagus nerve controls muscles resulting in voice resonance and also the soft palate. It is responsible for homeostasis of the digestive tract, and contracting the muscles of the stomach.   The vagus nerve controls the small and large intestines to help process food.  The vagus nerve also sends sensory signals to the brain about what is being digested and what the body is getting out of it.

Gastroparesis

Gastroparesis is a condition where the stomach takes too long to empty chyme into the duodenum of the small intestine.  This condition is also called delayed gastric emptying.  Damage to the vagus nerve causes disfunction in the contracting of the smooth muscles of the stomach.  This causes the food to move slowly through the alimentary canal or stop completely.  There are many varying symptoms of gastroparesis including pain in the upper abdomen, nausea, weight loss, abdominal bloating, heartburn, lack of appetite, stomach spasms, and gastroesophageal reflux.  The symptoms may range from mild to severe and may be aggravated by consuming high fiber foods like raw fruits and vegetables.  Gastroparesis is most often caused by diabetes.  The high levels of blood glucose damage the blood vessels carrying oxygen and nutrients to the vagus nerve and chemically alter the signals sent through the nerve.  The high levels of blood glucose eventually lead to damage to the vagus nerve.  If chyme lingers too long in the stomach bacterial overgrowth due to food fermentation may occur.  Gastroparesis is a chronic condition and is not cure by treatment.  Gastroparesis can be improved by dietary changes like avoiding the consumption of high fiber or high fat foods and eating six small meals a day rather than three large ones.

Damage to the Vagus nerve

Damage to the vagus nerve can result in trouble with moving the tongue while  speaking, or hoarseness of the voice if the branch leading to the larynx is  damaged.

Hearing loss may  result from damage to the branch of the vagus nerve that innervates the concha  of the ear.

Damage to the vagus nerve can cause cardiovascular side effects, including  irregular heartbeat and arrhythmia.

Literature Cited:

Gailard, F., Jones, J. 2005-2010. Cranial nerves. Radiopaedia.org; [updated 2011, cited 2012 Apr 18]. Available from: http://radiopaedia.org/articles/cranial_nerves

Gastroparesis [Internet]. 2007. National Digestive Diseases Clearing House. Bethesda (MD); [updated 2012 Mar 20, cited 2012 May 1]. Available from: http://digestive.niddk.nih.gov/ddiseases/pubs/gastroparesis/

Gastroparesis [Internet]. 2010. Youtube; [updated 2010 Dec 11, cited 2012 May 6]. Available from: http://www.youtube.com/watch?v=v-yeVxI4CeE

Gastroparesis Pictures [Internet]. 2011. Gastroparesis: All about gastroparesis; [cited 2012 May 1].  Available from: http://thegastroparesis.blogspot.com/2011/08/gastroparesis-pictures.html

Thackery, G. 1997. The cranial nerves. Loyola University of Medical Education Network; [updated 1997 Aug 28, cited 2012 May 1]. Available from: http://www.stritch.luc.edu/lumen/MedEd/GrossAnatomy/h_n/cn/cn1/mainframe.htm

Zieve, D., & Dugdale D. 2011. Treatment of epilepsy. Baltimore (MD). University of Maryland Medical Center; [updated 2009 Mar 29, cited 2012 May 1]. Available from: http://www.umm.edu/patiented/articles/treatment_of_epilepsy_000350.htm

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