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The Enteric Nervous System also called our second brain relies on the same type of neurons and neurotransmitters that are found in the Central Nervous System.

ENS is embedded in the wall of the gastrointestinal system stretching from the lower third of the oesophagus right through to the rectum. ENS, one of the main divisions of the autonomic nervous system that governs the function of the gastrointestinal tract.

The ENS plays an important role in triggering extreme emotional shifts such as Stress, Anxiety & Depression in people coping with IBS- Irritable Bowel Syndrome.

Stress can affect one’s nerves, and make the digestive system overactive.

Currently, we are trying to better understand the connection of ENS with CNS and “communication between the big brain and the brain in our gut.”

What is Gut-Brain ?

The gut-brain axis is a term for the communication network that connects your gut and brain. These two organs are connected both physically and biochemically in several different ways.

Neurons are cells found in your brain and central nervous system (CNS) that tell your body how to behave. There are approximately 100 billion neurons in the human brain.

Similarly, our gut contains 500 million neurons, which are connected to your brain through nerves in your nervous system.

The Role of Vagus Nerve.

The Vagus nerve is one of the biggest nerves connecting your gut and brain. It sends signals in both directions. For example, in animal studies, Stress inhibits the signals sent through the Vagus nerve and also causes gastrointestinal problems. Similarly, in humans it has been found that people with IBS have reduced vagal tone, indicating a reduced function of the Vagus nerve.

Our gut and brain are also connected through chemicals called neurotransmitters.

"Neurotransmitters" produced in the brain control feelings and emotions. Several neurotransmitters are also produced by our gut cells and trillions of microbes living there. Our gut microbes also produce a neurotransmitter called gamma-aminobutyric-acid (GABA), which helps control feelings of fear and anxiety.

Gut microbes also metabolize bile acids and amino acids to produce other chemicals that affect the brain.

Stress reduces the production of bile acids by gut bacteria and alters the genes involved in their production. Our gut-brain-axis is also connected through the immune system and inflammation by controlling what is passed into the body and what is excreted.

Problems related to the Gut-Brain.

If our immune system is switched on for too long, it can lead to inflammation, which is associated with many brain disorders like depression.

Lipopolysaccharide (LPS) is an inflammatory toxin made by certain bacteria. It can cause inflammation if too much of it passes from the gut into the blood. This can happen when the gut barrier becomes leaky, which allows bacteria and LPS to cross over into the blood.

Inflammation and high LPS in the blood have been associated with many brain disorders including severe depression.

"Stress" can perturb the composition of the gut microbiota and that enteric pathogens can affect host behaviour. The gut-brain-axis primarily combines the sympathetic and parasympathetic arms of the autonomic nervous system (ANS), which drives both afferent and efferent neural signals between the gut and the brain, respectively. The HPA axis meanwhile coordinates adaptive responses against stress including activation of memory and emotional centres in the limbic system of the brain.

The neuro-immuno-mediators of the Gut-Brain-Axis allow the brain to influence intestinal function- immune cells, epithelial cells, enteric neurons, and smooth muscle cells.