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The Brain Gut Connection in IBS


Updated May 22, 2014

Dysfunction in the connection between the brain and the gut may be a contributing factor in irritable bowel syndrome (IBS).

Some health problems are pretty simple to understand. If you have a sore throat, your doctor will take a tissue sample from your throat and run a test to see if you have a strep infection. A strange looking mole on your skin can be tested to see if it is cancerous. Unfortunately, IBS is far from simple. Unlike diseases that are visible, to understand what is going wrong in IBS, researchers have found that they need to look beyond the gut and toward the complex communication systems that connect the gut with the brain. To truly appreciate the work that is being done in this area, you would need to have a degree in neuroscience. Even without such a degree, it is helpful to have some basic understanding of the complex connection between the brain and the gut and how this relates to IBS.

Biology Basics

See if any of the following discussions ring a bell from your time spent in high school biology class. Communication among all of the parts of our bodies occurs through the passing of information from nerve to nerve. Here is a simplified description of the various pathways along which this communication takes place:

  • Central nervous system (CNS) –- the brain and the spinal cord
  • Peripheral nervous system (PNS) – nerve pathways that extend beyond the brain and spinal cord.

The peripheral nervous system is further divided into two parts:

  • Somatic nervous system –- responsible for voluntary control of muscles and reaction to external sensations.
  • Autonomic nervous system – responsible for the motor and sensation responses of our internal organs (viscera).

Enteric Nervous System

The enteric nervous system (ENS) is a part of the autonomic nervous system that is responsible for regulating the process of digestion. The ENS manages motility (movement of muscles), secretion of fluid and blood flow. The ENS handles so much responsibility on its own that it is sometimes given the name “the little brain.” Given this description, it is easy to see that understanding how the enteric system operates is essential to an understanding of what may be going wrong in a body with IBS.

Up the Down Staircase

Communication is a two-way street when it comes to the brain (central nervous system) and the digestive system (enteric nervous system). Complex pathways link the brain and the intestines with information flowing back and forth on a continual basis. This close connection is most clearly seen in our response to stress (perceived threat), which suggests that this complex communication network was very important for our survival as a species.

Researchers are finding evidence that dysfunction along these up and down pathways may be contributing to the abdominal pain, constipation and/or diarrhea that are the symptoms of IBS. Nerves in the gut that are experiencing excessive sensitivity can trigger changes in the brain. Thoughts, feelings, and activation of parts of the brain that have to do with anxiety or arousal, can stimulate exaggerated gut responses. Malfunction may also be found along the many different pathways that connect the brain and gut. For instance, there is evidence that abnormal functioning along two separate pathways in the autonomic nervous system is associated with the symptom of diarrhea vs. the symptom of constipation. In general, it seems that dysfunction in the brain-gut communication system is interfering with the body’s ability to maintain homeostasis, a state in which all systems are working smoothly.

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