The Enteric Nervous System: The Brain in the Gut

gut brain connection

Did you know that many diseases could be traced to a breakdown in the gastrointestinal tract? Do an internet search for neurotransmitters and the common result will be: “Neurotransmitters are biochemicals produced in the brain that affects us mentally, emotionally and physically.”  Despite the fact that Ninety nine (99%) percent of the neurotransmitters in your body are actually created in the gastrointestinal tract (GI tract or your Second Brain), and every brain chemical known as a neurotransmitter is found there.  Doing some quick math, this means that the majority are focusing on the the 1% formed in the brain and ignoring the 99% made in the gut.

For proper thyroid function, 20% of the thyroid hormone in your body must be converted into its active form, which is done in the GI tract. The secretion of TSH is inhibited by elevated levels of dopamine, and stimulated by elevated norepinephrine. Conversely, a study published in 1987 in the “European Journal of Endocrinology” found that low levels of dopamine were associated with elevated thyroid hormone levels in patients with Graves’ Disease. The effect of Serotonin pathways remained an open question. This means the GI tract, or gut, plays a very important role in achieving optimal thyroid health.

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Seventy (70%) percent of your immune system resides in this area – your gut, and the GI tract has many important functions for your health including digestion, nutrient absorption, elimination, detoxification, hormone metabolism and energy production.

The gut has a mind of its own, the “enteric nervous system”. Just like the larger brain in the head, researchers say, this system sends and receives impulses, records experiences and respond to emotions. Its nerve cells are bathed and influenced by the same neurotransmitters.

The gut can upset the brain just as the brain can upset the gut.

The brain is protected by the blood-brain barrier.

The gut has no such protection.

The Second Brain or the “enteric nervous system” is located in the sheaths of tissue lining the esophagus, stomach, small intestine and colon. Considered a single entity, it is a network of neurons, neurotransmitters and proteins that zap messages between neurons, support cells like those found in the brain proper and a complex circuitry that enables it to act independently, learn, remember and, as the saying goes, produce gut feelings

The gut’s brain is reported to play a major role in human happiness and misery. Many gastrointestinal disorders like colitis and irritable bowel syndrome originate from problems within the gut’s brain. Also, it is now known that most ulcers are caused by a bacterium not by hidden anger at one’s mother.

Details of how the enteric nervous system mirrors the central nervous system have been emerging in recent years, according to Dr. Michael Gershon, professor of anatomy and cell biology at Columbia-Presbyterian Medical Center in New York. He is one of the founders of a new field of medicine called “neurogastroenterology.”

The gut contains 100 million neurons – more than the spinal cord. Major neurotransmitters like serotonin, dopamine, glutamate, norephinephrine and gasotransmitters like nitric oxide, carbon dioxide and hydrogen sulphide are in the gut. Also two dozen small brain proteins, called neuropeptides are there along with the major cells of the immune system. Enkephalins (a member of the endorphins family) are also in the gut. The gut also is a rich source of benzodiazepines – the family of psychoactive chemicals that includes such ever-popular drugs as Valium and Xanax.

SSRIs (Selective Serotonin Reuptake Inhibitors) are believed to ease depression by enhancing levels of Serotonin to the brain. But 95% of the Serotonin in the body lies in the digestive system, and diverting the supplies of Serotonin from their natural receptors can increase anxiety, alter sleep patterns, cause sexual dysfunction and adversely affect the cardiovascular region. Balancing the hotbed of Serotonin production in the gut is critical to restoring the balance. Some scientists believe that SSRIs block Serotonin in the gut and change the signals to the brain, since antidepressants prevent the uptake of Serotonin by cells that should be using it. But Serotonin is necessary to stimulate the digestive tract for bowel movements. This may explain why some SSRI users experience nausea, stomach upset, constipation, diarrhea, and fluctuations in appetite.

GABA receptors for Benzodiazepines and Sleeping Pills are also located in the gut and depress gastrointestinal movement, which can cause constipation. But the continued use of medications that target GABA also increase the level of stress on the body. And in many ways, the connection between stress and the gut may be the most visible brain-gut connection.  Chronic stress can result in indigestion, ulcers and a host of uncomfortable symptoms, including colon spasms. This may explain why the gut naturally produces benzodiazepines, to keep the natural state of calm that is necessary for proper functioning.

Nearly every chemical that controls the brain is also located in the stomach region, including hormones and neurotransmitters such as Serotonin, Dopamine, Glutamate, GABA and Norepinephrine. The gut contains 100 million neurons – more than the spinal cord. But there are also two-dozen small brain proteins; major cells of the immune system; one class of the body’s natural opiates; and native benzodiazepines. The gut, known as the enteric nervous system, is located in sheaths of tissue lining the esophagus, stomach, small intestine and colon, and plays a key role in human emotions. But few know the enteric nervous system exists, and therefore gut health is often overlooked.

Symptoms from the two brains can get confused, and just as the brain can upset the gut, the gut can also upset the brain. The brain signals the gut region by talking to a small number of command neurons, which in turn signal relay neurons that carry messages and control the pattern of activity in the gut. The term Solar Plexus simply refers to the nerves in the abdomen. But these plexuses also contain cells that nourish neurons and are involved in immune response and the protection of the “blood brain barrier” to keep harmful substances away from the important neurons. There are also sensors for sugar, protein, acid and other factors that monitor the progress of digestion, determining how the gut mixes and handles it’s contents.

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5 thoughts on “The Enteric Nervous System: The Brain in the Gut

  1. After reading this and the gasotransmitters articles, I have a feeling that the usual probiotics aren’t necessarily the solution here!!!!

    • Do not mistake what I’m about to say. I am not anti-probiotic. I am pro proper use of probiotics with the appropriate probiotics. The thing to understand about probiotics is that by the time they get to the store most are dead and/or other strains have taken over. They are not shipped in a refrigerated truck nor held in the stock room in a refrigerator. Most are probiotics are dead and you are supplementing with the carcasses (dead bodies) of bacteria. The dead bodies of bacteria stimulate the immune system to clear them out of your body. Thus probiotics are an “immune stimulant.” In an unhealthy gut, these dead bodies can cross the gut barrier provoking a further immune response. For a healthy person, immune stimulation is not a bad thing. For an autoimmune person, with an already overstimulated, un-regulated immune system any provocation of the immune system is a bad thing. If probiotics cured all they claim to there would be no disease. For more info on probiotics:

      • This is probably why I felt that the probiotics has failed me. It is always a pleasure to read your articles. Many thanks!!

  2. As I understand it, probiotics bred in the lab have lost the ability to adhere to the gut wall so they provide benefit only as long as you keep taking them. Not very satisfactory. Poo transplants end up looking like the best probiotic there is but then the diet has to be changed in order to feed the new biota.

    • I agree that most probiotics have lost the ability to adhere to the gut wall because most are “dead.” Taking the dead probiotics provokes the immune system to clean up their carcasses. So they are an immune stimulant.
      As to the latest craze. As you so aptly put it “Poo” transplant. Whether Fecal transplants are done in a hospital or at home. Yes, I have heard of people doing home Poo transplants. This is the equivalent of bussing kids from the suburbs to ghetto schools expecting them to change the ghetto environment. While good intentioned the suburban kids only get ghettoized. The ghetto just like the gut is a primal environment, where the environment controls the behavior of those who live there.
      Hepatitis and HIV is a major problem with Poo transplants. The medical community recognizes this and has decided to screen possible donors for past history of Hepatitis or HIV. Considering the gut environment of the donors, some say 80% of the population have digestive issues. Simply transplanting Poo from a person with lesser digestive issues to a person with greater digestive problems will not change the gut environment. We must be aware of and look at the behavior of the individual microbial species.
      Yes, the gut environment controls the microbial “behavior.” The gut environment is controlled by the digestive sequencing and chemistry (terrain). The digestive sequencing and chemistry controls how the food is broken down and processed or not! If the digestive terrain is not restored the microbes will change and adapt their behavior to the gut environment. I think Poo transplants are opening up a whole new can of worms. A little parasite humor there. By the way they are also doing worm probiotics now. And finally, I’ll let Jeff Goldblum say it:

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