So Who is Really In Charge? The Relationship Between the Stomach and Brain Explained
We have all heard the saying “two brains are better than one,” but what we picture is two heads thinking. What if you were told that your body actually possesses two brains instead of one? Emotional transference occurs with both the brain and the digestive system. These intricate and multifaceted systems communicate feelings back and forth to one another. Ever felt that “gut-wrenching pain” experience? How about the nervous “butterflies” before a big event or the feeling like your throat is closing up on you, even though there is nothing physically responsible for the sensation; that you are quite literally “choking up with emotion?” That’s because there is a direct, responding relationship between emotional stress and physical distress or their positive equivalents. Is it any wonder that we digest optimally when we are happy?
Every complex cell, structure, organ, and encoding starts off as two cells join together. From there, division and specialization occur and continue until a new, functioning human is created. Our brain (central nervous system) and digestive system (enteric nervous system) are fashioned from the same basic tissue and are connected via the Vagus nerve. Also known as the pneumogastric nerve or the Wanderer, the Vagus nerve is tenth of the twelve paired cranial nerves and supplies parasympathetic motor fibers to all organs except the adrenal gland, from the neck to the transverse part of the colon, although 80 – 90% are sensory nerves that convey information to the brain and vice versa.
From an evolutionary standpoint, it makes sense for the body to have two brains. The Enteric nervous system most likely antedates the Central nervous system and is ancient in evolutionary terms. Newborn animals did not have the experience of living that provides for higher brain function. However, they do require the need to eat and digest food from birth on. As life changed and evolved, animals needed a more complex brain for finding food and ensuring reproduction, and this is where the central nervous system came into effect. The gut brain was too important, or so nature deemed, to have been housed in the cranial capacity with long cords relaying down so the Enteric nervous system preserved its independent status.
The Enteric nervous system is a network of over 100 billion neurons in the gut that not only can signal our bodies to stress but can also cause illness. Many of its structures parallel those of the mainframe brain. The gut is like a little chemical lab. Nearly every chemical found in the brain also exist in the gut. There are sensory and motor neurons (information processing circuits), and the glial cells. There are even classes of chemicals that are in the same family as psychoactive drugs – drugs that include Valium and Xanex – called benzodiazepines. Dopamine, serotonin, acetylcholine, nitric oxide and norepinephrine are major transmitters that are used by the gut as well. The gut monitors pressure, detects nutrients, measures acids and salts, and controls the process of digestion; all of this independent of the “higher” brain. In fact, should the communication wire between the two, the Vagus nerve, be severed, the gut will still continue to operate on its own.
Essentially what brains do is control behavior. For all situations – environmental responses – that present themselves, the brain or gut must assess conditions and decide upon a course of action then initiate an appropriate (most of the time) reflex. It is not just in digestion that these two systems are linked. During sleep, the brain has a 90 minute cycle, as does the gut. In fact, the gut goes through a REM cycle approximately the same time as the brain does. In a stressful situation, the brain releases chemicals that prompt the body to prepare for flight or fight action. This process basically “shuts off” the function of the gut and prepares it for potential trauma by sending signals to immunological mast cells in the intestines. These specialized cells secrete histamine, prostaglandins, and other agents that produce inflammation which is a protective function in case injury occurs. The rest of the body is just a few cells away from the dirty contents of the digestive system.
The main transmitter used by the GI tract is serotonin – the chemical that, when released properly, gives you that happy, contented feeling after an especially tasty meal. 95 % of the body’s serotonin resides in the gut. This chemical is responsible for the mostly one way informative communication to the brain, acting as a go-between, giving constant updates on the stasis of the gut. Normally, after serotonin is released into the gut and initiates an intestinal response, it is then whisked out of the bowel by serotonin transporters (SERTs), which are found in the cells that line the wall of the intestinal tract. Those that suffer from IBS have issues with their SERTs not reuptaking the serotonin correctly, leaving too much floating around and causing diarrhea. Parkinson’s and Alzheimer’s lesions and plaques that are found in the brain are also found in the gut. The nerves in the gut are as sick as the nerves in the brain. Doctor’s attribute some gastrointestinal issues to being psychosomatic, as they been unsuccessful in determining a physical cause for the discomfort. Children that have been diagnosed as autistic are often afflicted with abdominal pain. The majority of patients that suffer from anxiety or depression will also have altercations in their GI systems. It’s drugs like Prozac that interfere with the serotonin reuptake, leaving a more abundant supply to roam around in the intestines. These correlations are starting to prove the mind over matter theory. It makes sense that drugs that have an effect on the brain would also have an effect the gut.
The human gut has long been a repository for good and bad feelings, detectable to those who pay attention to them. When you take care of one, you are taking care of the other. The relationship between the brain and the gut is an unfolding story- it sheds light onto the evolutionary process of nature and offers us a glimpse into our nervous system and our minds.