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  • Writer's pictureJoan Rothchild Hardin

Our Second Brain – The Gut Mind

During vertebrate embryonic development, a single clump of fetal tissue divides to grow into the gut and the brain. One section becomes the central nervous system (the brain and spinal nerves) while another migrates lower in the body to create the enteric nervous system embedded in the sheaths of tissue lining the esophagus, stomach, small intestine and colon.

The two separate nervous systems connect via the vagus nerve running from the brain stem into the abdomen. This major trunk line is one of the longest nerves in the body. The gut and the brain are constantly signaling each other, back and forth, along the vagus nerve and also via chemicals released by the gut and transported to the brain. When one brain gets upset, the other becomes upset too. They work in conjunction with each other along the Gut-Brain Axis, each heavily influencing the other. (Champeau, 2013); (Gershon, 1998); (Foster, 2013)

At birth there are about one million brain cells in our guts. We now know that the neurotransmitter serotonin enables growth of new neurons in this second brain – even in adulthood. This knowledge suggests we’ll learn how to repair a damaged or congenitally defective enteric nervous system one day without resorting to invasive procedures. (Paddock, 2009)

Gastro-intestinal Tract

Take a look at next page on The Gut Microbiome – Our Second Genome for some truly mind boggling information on this second brain of ours.

In 1683 in Delft, when the Dutch haberdasher turned lens maker, Anton van Leeuwenhoek, peered through one of his primitive microscopes at scrapings he’d taken from his own teeth and became the first person to observe what he termed “animalcules” living in the tartar, he unknowingly launched the fascinating field of microbiology. But he surely had no idea what would be discovered with high power equipment in our own age.


Champeau, R. (2013) Changing gut bacteria through diet affects brain function, UCLA study shows. See

Foster, J. (2013). Gut Feelings: Bacteria and the Brain. The Dana Foundation. See

Gershon, M.D. (1998). The Second Brain: A groundbreaking new understanding of nervous disorders of the stomach and intestine.

Paddock, C. (2009, August 5). “Not Only Does Our Gut Have Brain Cells It Can Also Grow New Ones, Study.” Medical News Today. See

A version of this page content will appear in my forthcoming 2014 Oriental Medicine Journal article THE MICROBIOTA-GUT-BRAIN AXIS: The constant two-way communication between our guts and our brains.

© Copyright 2013-2014 Joan Rothchild Hardin. All Rights Reserved.

DISCLAIMER:  Nothing on this site or blog is intended to provide medical advice, diagnosis or treatment.


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