Brain-Gut Axis Connection – by Naveed

Brain-gut axis signifies the relationship between events that affect the function of the central nervous system (brain) and the influence these factors ultimately have on the function of the intestines via the specialised enteric nervous system of the intestine.


The three key players in the brain-gut axis include gastrointestinal tract (GIT), the central nervous system (CNS) and the enteric nervous system (ENS)


During early fetal development both the gut (esophagus, stomach, small intestine and colon) and the primary brain start to develop from the same clump of embryonic tissue. When this piece of tissue is divided, one piece grows into the brain or the Central Nervous System (CNS) and the other section becomes the gut or the Enteric Nervous System (ENS).


During later stages of fetal development, these two brains then become connected via a massive nerve called the vagus nerve. The vagus nerve is the longest of all our cranial nerves and creates a direct connection between the brain and the gut. Because of this direct brain-gut connection, the state of the gut has a profound influence on our psychological well being.


In recent years, the link between the nervous system and the digestive system has been recognized. It has been shown that is a constant exchange of chemicals and electrical messages between the two systems and many scientists now often refer to them as one entity ‘the brain-gut axis’. Therefore, what affects the bowel will directly affect the brain and vice versa.


The gut’s brain, known as the enteric nervous system (ENS) is located in sheaths of tissue lining the esophagus, stomach, small intestine and colon. Considered as a single entity, it is packed with neurons, neurotransmitters and proteins that zap messages between neurons or support cells like those found in the brain.


The means by which one nerve cell communicates with the next is through chemicals called neurotransmitters. An extremely important neurotransmitter for digestive functioning is serotonin (5-HT). It is estimated that up to 95% of the serotonin in the human body is found in the digestive tract. Serotonin is considered to be a vital part of the communication system between the brain and the gut. Serotonin seems to play a part in motility, sensitivity and secretion of fluids. Movement, pain sensitivity and the amount of fluid in the stool are all affected by it.