A Tryst with your Second Brain

This image shows the enteric nervous system of a four-day-old mouse, with blood and lymphatic vessels (blue), neurons (pink), and support cells called Schwann cells (green).
Immunofluorescence of the alimentary canal. Uesaka et. al., J. Neuroscience., 2015.

Most people are commonly accustomed to the fact that the brain is the seat of all logical reasoning and action that is made by us as an individual. But more often than not, when our mind and brain fails to give us a fair judgement of the situation, we are told to go with our gut. But have you ever thought about whether this gut feeling is truly something induced by our sixth sense, or is it merely the presence of a second brain, an equally responsive and powerful set of neurotransmitters which may remotely be more powerful than the boss of decision making?

The enteric nervous system as we know it, is precisely multiple sheaths of neurons embedded in our alimentary canal which measures about nine metres end to end from the oesophagus to the anus and contains more than 10 million neurons! Now a layman, who is not particularly familiar with the concepts of how the body functions, often feels a certain turmoil inside the stomach during times of stress. It may very well be concluded that this is not a random feeling arising from the situation but merely the signal sent by the neurotransmitters in the alimentary canal which makes us feel the way that we do. The second brain is a very powerful set of neurons which determine a wide range of activities from whether our food intake is suitable for the body, when we are hungry, whether or not we have over eaten and so on. Thus the feeling of uneasiness when we suffer from an acid reflux or a gastrointestinal problem is nothing but a series of signals transmitted by the vagus nerve which innervates this tract.

Layers of the Enteric Nervous System. Nature News, Mucosal Immunology.

Since researchers have found a very direct link between the stomach and the brain, it is increasingly being used in experiments to try to cure depression and find a possible treatment for autism. Given that the brain is so dependent on the neurotransmitters in the alimentary canal, some researchers have shown that an electrical stimulation of the vagus nerve and modifying the signals can in a way lead the brain to achieve a possibly happier state. But on the flip-side, medications for depression can in a similar way have a negative effect on the gastro-intestinal system of an individual. The serotonin seeping from the second brain might possibly play some part in autism. In fact, nearly 90% of serotonin (“the happy chemical”) in our body has been shown to be secreted from the gut. The genes that help in forming a synapse (an electro-chemical junction) in the brain also help in forming a synapse in the gut muscles. Now, since this gene is not functional in patients identified with autism, gut related problems such as peristalsis and churning of food is a widely noticed symptom in such patients along with problems in motor development. In a new Nature Medicine study, a drug that hindered the release of serotonin from the alimentary canal in a way prevented the bone-deteriorating disease osteoporosis in postmenopausal rodents.

Gut Flora. Zimmerman et.al., Yale University.

The presence of microbiota in the gut significantly impacts certain diseases in the brain and various disorders. Since the gut is responsible for controlling the body’s immune responses, it can in a way be said to protect the body. The composition of microbiota in the gut largely determines a diverse range of physiological consequences. For example people who have been exposed to greater micro organisms automatically have a better immune system as opposed to those who are not. This is the simplest explanation to why people in third world countries automatically have a greater immunity to diseases as opposed to those who’ve grown up in protected urbanised and sophisticated households. The microbes in the gut also determine how well people are able to digest their foods thereby alluding to the basic reason behind the various gastro-intestinal problems. The cross-talk between the gut microbiota and the brain, mediated by various chemical signals, is certainly crucial in the normal functioning of our body. Thus the various problems of obesity and acid refluxes stem from the basic fact of the presence or absence of these excessively essential microbes in our gut.

Source : googleimages.com

All in all, our second brain is as important as our brain. The brain does not normally expend too much energy on the tasks of digestion and excretion, which is why the responsibility has so carefully been handed down to the second brain. This doesn’t disprove the importance of our brain, however! It still remains the master planner of our minds. But, like any company or organization where the major hard and tedious tasks are done by those lower on the hierarchy, the second brain in a similar way carries out those tasks for the body. The importance of both our brain and second brain is equal in making our bodies receptive and functional at all points. But the next time someone asks you to trust your gut while making a decision, make sure to consider the fact that it is an equally well thought out and considered decision.

Go with your gut!


[1] Haridy R. 2018. ‘Unique Neuronal Firing Patterns in our “Second Brain” observed for the first time.’ Science.

[2] Underwood E. 2018. ‘Your Gut is directly connected to your brain, by a newly discovered neuron circuit.’ Science.

[3] Hadhazy A. 2010. ‘Think Twice : How the Gut’s “Second Brain” Influences Mood and Well-Being’. Scientific American.

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