The Nervous System and the Gut Brain a/k/a the Enteric Nervous System

I want to start today by being clear as to who deserves the credit for the knowledge and function of the gut brain that I am sharing with you in this blog. His name is Michael D. Gershon, M.D., Professor and Chairman of the Department of Anatomy and Cell Biology at Columbia University. His is the recognized father of the field of neurogastroenterology, the study of the gut brain, also known as the enteric nervous system. He is also the author of The Second Brain: Your Gut Has a Mind of Its Own, which was published in 1998 by HarperCollins.

I have found his work and book to be extremely inspirational in opening the doors of possibility in identifying potential root causes of neurological issues like migraine and digestive issues like IBS. I cannot encourage you enough to read his book. I must also warn you that the book is a difficult read, even some of my doctor friends have considered it challenging. Consequently, I have written an electronic “cliff notes” version of the book that I am happy to share with you. Simply send an email request to tom@foreverwell.com and I will send you a copy. By the way I met Dr. Gershon at Columbia and gave him a copy of my effort. He seemed pleased that someone was trying to get the word out.

Today we are going to discuss the body’s nervous system, as identifying its structures will provide the understanding of how the gut brain fits into the system and allow you to see some possibilities as we later discuss that IBS and migraine may very well have common root causes.

However, first I want to make a few comments on the study reported yesterday in the national news regarding the link between attention deficit hyperactivity disorder (ADHD) and residual pesticides in those who suffer. If you spend any time on our ForeverWell website (www.foreverwell.com) you understand that we believe that most all chronic illness is caused by the breakdown of normal function of the body. More specifically we argue that the breakdown is caused by two major, yet simplistic factors, either the body is not getting something that it needs, a combination of dietary choices and how well the digestive system is functioning, or the body is not eliminating something it cannot use, that is, the body to some degree or another is toxic.

I find this study interesting because it shows a direct link between a chronic illness/disorder and poor detoxification. Clearly it supports our arguments about the root causes of disease. Many in the ADHD community believe there is a genetic component or cause. We would argue that that genetic predisposition may very well be triggered by an unmanageable toxic load. This study, and if you did not see the report just put ADHD and pesticide into any search engine and you will find that all major news agencies filed stories on the subject yesterday, shows that our neurological systems are susceptible to the effects of toxicity.

It is important to realize that while it is easy to see pesticides as toxins; our bodies are bombarded by toxicity from a variety of sources. In addition to pesticide and herbicide residue in our foods there are also toxins in the air we breathe and the water we drink. Our bodies create toxins in the process of life. Our metabolism, the burning of our energy at a cellular level creates waste products that must be removed from the body. If our organs of detoxification are not functioning at an optimum level we can be toxic without the effects of external sources like pesticides.

Is it possible that a level of toxicity that seems to create ADHD in children could affect another person’s nervous system in a way that results in IBS or migraine?

Now on to our conversation about the structure and function of the body’s nervous system and how the gut brain fits into this system. Our nervous system is very complex and yet there is simplicity to the basic plan.

We can look at the entire system as being composed of a central nervous system (CNS) and a peripheral nervous system (PNS). In this view the head brain and the spinal cord make up the CNS and the PNS includes everything else. While there is a great deal of synergistic operation between the systems, the central nervous system is clearly in charge. Direction flows from the CNS to the peripheral system and information detected by the body’s sensory receptors travels back to the central nervous system for analysis.

The PNS can be further divided into the voluntary nervous system and the autonomic nervous system. The voluntary system allows for our conscious movement of our skeletal and muscular systems while the autonomic regulates bodily function outside our consciousness such as breathing, heartbeat, digestion and internal reaction to stimulus. The autonomic system is further divided into the sympathetic and parasympathetic systems. The sympathetic system responds to danger or stress. It raises the heart rate and blood pressure, stimulates the release of cortisol and adrenaline, the stress hormones, and essentially is that part of the nervous system that prepares us for fight or flight. The parasympathetic system on the other hand, is playing its role when someone is relaxed, lowering heart rate and blood pressure and in general down regulating our internal systems. Additionally, the parasympathetic system stimulates the process of digestion.

For most of the 20th century the gut brain, also known as the enteric nervous system was considered part of the parasympathetic nervous system. And that made a lot of sense because it was pretty obvious that when you are in a stressful situation, when the fight and flight mechanisms are in charge you are not thinking of digestive function. In the most severe cases of impending danger, your digestive system literally shuts down. This is because the sympathetic system is fully activated and in charge and directing internal mechanism that divert the body’s energy to large muscle groups…legs for escaping the danger and arms for defending oneself. In contrast when the body’s mechanisms are down regulated by the parasympathetic system the body has the energy available to operate the digestive processes.

It was Dr. Gershon and his colleagues whose discoveries began to force the scientific community to rethink their classification of the enteric nervous system as simply part of the parasympathetic system. The first and most obvious bit of information in their path to discovery was that compared to the number of nerve cells in the nerve complexes of the gut brain, the number of motor nerve fibers connecting the brain or spinal cord to the gut is incredibly small. It appears that there are some two thousand nerve fibers heading from the vagus nerve to the gut and yet there are over one hundred million nerve cells in the human small intestine. This aspect of the enteric nervous system was completely out of sync with the conditions that allowed for the classifications sympathetic and parasympathetic.

As Gershon states “The enteric nervous system differs from the sympathetic and parasympathetic in its anatomical and functional independence from the brain and spinal cord. It is this separate-but-equal classification of the enteric nervous system that still surprises audiences of doctors and even neuroscientists”.

Further research has revealed, as I mentioned in an earlier post, that the nerve structures of the gut brain have been shown to have decision making capacity. This requires the presence of interneurons.

Again to quote Gershon, “Interneurons are the cells that add the layers of complexity and sophistication that distinguish the central and enteric nervous systems from the banal peripheral ganglia found outside the bowel. The nerves of the gut do not just slavishly pass signals from sensory receptors to muscles, glands, or blood vessels. Because of its interneurons, the enteric nervous system can modulate and process the information it receives. Serotonin, I speculated, as the neurotransmitter of an interneuron, might be one of the molecules that enable the bowel to function as an independent information-processing center, i.e. a second brain.”

The research is absolutely definitive that our gut brain operates most of the digestive processes without any direction from the central nervous system. The gut brain is orchestrating the various aspects of digestion because it has the ability to make decisions and direct the organs of digestion on its own.

With this information in hand you might find it interesting, as I did, to do a search on IBS and the gut brain. While it might seem less obvious that there is a connection between the gut brain and migraine (we will get to that later) it would seem entirely obvious that the gut brain could be having a causative role in IBS. However when you read the various sites that come up when you do an IBS gut brain search they are still focused on the brain gut connection, trying to make the claim that the head brain is still in charge of the digestive processes. There seems to be an effort to downplay the research and insights that Dr. Gershon and others in the field of neurogastroenterology have provided.

Enough for now, more to come, I would appreciate your thoughts and comments.

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