There are many branches of the human nervous system. It seems to most of us that a scientific explanation seems overwhelming and confusing.  The nervous system is incredibly complex and very difficult to understand.  The focus of this article is to better understand he 10th cranial nerve; also known as the vagus nerve.  The vagus nerve controls so many things and sometimes, those things go wrong.  Some results of nerve dysfunction can be successfully managed with medications.  Hopefully, the science-symptom connection will make more sense after reading this article.

Our nervous systems consist of the brain, spinal cord, and all those little nerves that connect in between. Collectively, they control the body’s senses, thoughts, and movements. The brain and spinal cord form the central nervous system (CNS). The CNS is the headquarters.  All the in between sensory nerves and nerves helping organs function form the peripheral nervous system (PNS).  Most of the nervous system functions we are used to happen in the PNS.  This is where things get a bit confusing.

The Peripheral Nervous System

The PNS has a couple sections.  The first section is called the Somatic.  It includes all of our voluntary movements.  It moves our bones, muscles in our arms and legs, and helps us move around during exercise.  The second section is called the Autonomic.  The Autonomic work with involuntary movements, those with which are unaware of and have no control over.  It works to carry nerve impulses from the CNS to those breathing muscles and sweat glands we use during exercise.  The Autonomic also helps our organs communicate with our brains.  When we are digesting food and our heart rate is changing, our Autonomic nervous system is hard at work.

The Autonomic Nervous System

To delve a little further, the Autonomic has a couple sections as well.  the Sympathetic is what we call the classic “fight or flight” system.  When placed in situations of stress or danger, the body reacts by increasing breathing and heart rate.  Stress hormones are released and digestion slows down.  The Sympathetic nervous system is also responsible for dilating our pupils in dim lighting.  Stressful times call for desperate measures.

The second piece of the Autonomic os the Parasympathetic.  This division is coined “rest and digest.” It responds when the body is relaxed, resting, or eating. This branch also helps calm the body and undo any work done by the Sympathetic.  The Parasympathetic system works to slow breathing and heart rate, increase digestion and intestinal movements, and constrict pupils.  Stimulating saliva to enjoy tasting a yummy meal is another Parasympathetic function.

Cranial Nerves

The brain is the hub of everything.  Without it, we wouldn’t be able to walk, eat, talk, or breath.  There are some special nerves in the brain called the Cranial nerves.  They peak out from the underside of the brain and are considered part of the Central nervous system. There are 12 cranial nerves.  Each one is a pair; one on each side of the brain.  Cranial nerves are called by roman numerals.  They provide direct connections to the brain for special sensory organs such as muscles in the head, neck, and shoulders. They also innervate (supply with nerves) the heart and gastrointestinal tract.

The 12 Cranial Nerves:

  1. Olfactory: sense of Smell
  2. Optic: sense of sight
  3. Oculomotor: eye movement
  4. Trochlear: eye movement
  5. Trigeminal: facial movement and sense of touch
  6. Abducens: eye movement
  7. Facial: facial expression and sense of touch
  8. Vestibulocochlear: hearing and balance
  9. Glossopharyngeal: movement of tongue and throat
  10. Vagus: movement of heart, lungs, gastrointestinal, trachea, and esophagus
  11. Accessory: movement of the head, neck, and shoulders
  12. Hypoglossal: speech, chewing, and swallowing

The Vagus Nerve and Digestion (Cranial Nerve X)

My special interest is digestion.  After having a child with severe digestive dysfunction, I have learned more about the nervous system than I ever wanted.  There are a few cranial nerves that help with chewing, swallowing, and digestion. The oculomotor, trochlear, and abducens nerves (III, IV, VI) help with chewing. The glossopharyngeal nerve (IX) helps with swallowing. The hypoglossal nerve (XII) moves the tongue for swallowing.

The major cranial nerve that plays a role in digestion is the vagus nerve (X). The vagus nerve follows from the brain through the neck and torso. It carries information from organs to the brain. It also delivers information to organs such as the stomach and lungs.  The vagus nerve helps us feel hungry or full.  It helps our stomach prepare to sit and eat a great meal with friends.  The vagus nerve also helps break down that meal after it tells us we are full.  Emptying the stomach while it tells the pancreas to create digestive enzymes is important for calories.  The vagus nerve takes care of that too.  The vagus nerve also helps our lungs, heart, liver, and kidneys, amongst others.  Without it, our bodies wouldn’t know what to do with all those signals from the brain.

A Quick Anatomy Recap

  • Our body’s Nervous System has two sections: the Central nervous system (CNS) and Peripheral nervous system (PNS)
  • The Peripheral also has two sections: the Somatic nervous system (SNS) and Autonomic nervous system (ANS)
  • The Autonomic again has two branches: The Sympathetic and Parasympathetic
  • The brain has 12 pairs of cranial nerves that are part of the Central nervous system
  • A cranial nerve called the vagus nerve is the one with the most responsibility when it comes to organ functions. It carries information from the brain to the organs.
  • The vagus nerve increases digestion and stimulates the emptying of the stomach contents into the small intestines.

Nervous System Medications

When the Nervous System goes awry, there are many medication options to help alleviate symptoms.  Depending on the symptoms and causes, specific organ system medications are chosen.  Overall nerve pain medications include phenytoin (Dilantin), gabapentin (Neurontin).  Even Selective Serotonin Reuptake Inhibitors- SSRIs- (used to treat depression) can help.  The most common are duloxetine (Cymbalta) and vanlafaxine XR (Effexor XR).

I know I have repeated myself a few times in this post, but I find the nervous system to be extremely confusing! I know hearing things over and over again in different words can help solidify concepts that can then be used when making good medical decisions. I hope this post has been a source of clarity for all of you when looking at the nerves involved in digestion.


Kathryn Rohr is a freelance writer from KingsBlog specializes in digestive and nutritional health.  She believes accurate and valuable information should be easy to find!