The brain in your head is not your only brain. There is a 'second brain' in your intestines that contains 100 million neurons.
Ever wonder why you get cramps when you're stressed? Or why you get "butterflies" in your stomach before a job interview? And why your gut tells you not to trust a certain person?
Scientists say it's because the body has two brains -- the familiar one encased in our skull and another more obscure one in our gut. This "second brain," known as the enteric nervous system, is located in our digestive tract and holds about 100-million nerve cells- more than in our spinal cord.
Less complex and smaller than our cranial brain, this "second brain," which contains between 70 to 85 percent of the body's immune cells, is an independent data-processing center handling a complicated circuitry of neurons, neuromodulators, and neurotransmitters.
"Every neurotransmitter that exists in our brain also exists in the gut without exception. The brain in the gut is simply the brain gone south," says Dr. Michael Gershon, author of The Second Brain, and chairman of the department of anatomy and cell biology at Columbia University College of Physicians and Surgeons.
In 1899, anatomists and physiologists studying dogs found that, unlike any other reflex, the continuous push of material through the digestive system continued after nerves linking the brain to the intestines were severed. In other words, they discovered the gut had a mind of its own.
Operating like our brain and looking uncannily similar to it, the gut-brain responds to stimulus and is continuously active whether we're aware of it or not. But it doesn't think or feel. The feeling is held in the cerebral cortex of the brain. This "second brain" performs a different role.
"The brain in the head deals with the finer things in life: religion, philosophy, appreciation of art and music, creativity, etc.," says Dr. Gershon. "Whereas the brain in the gut deals with this dirty, messy and disgusting business of digestion. The brain in the head doesn't have to get its hands dirty with that kind of thing since it has delegated the job."
They may have different roles but our two brains are interconnected. One thousand to 2,000 nerve fibers connect them and enable the two to talk. When one gets upset, the other one does too.