He’s so gorgeous; you want to ask him out on a date, but you’re having trouble saying the right words. Your stomach is churning and fluttering. You feel a little sick, and you might have had a little diarrhea (of course he doesn’t need to know that).  What is happening to you is perfectly normal: you’re nervous, and you’ve got butterflies in your stomach. But that’s hardly a scientific explanation for what is going on. After all, you don’t really have insects fluttering around your belly. Do you?

Stomaching the brain

Of course not! But what you do have is a second brain hiding in the human stomach. This brain houses around 100 billion nerve cells in our digestive tract (which is more than those found in the spinal cord).

While the Central Nervous System is made of your brain and spinal cord, the gut’s brain is called the Enteric Nervous System (ENS). It is found in the tissue that lines the oesophagus, stomach, small intestine and colon.  It’s called a system because it is a complex network of neurons, chemicals that help neurons communicate with each other (neurotransmitters) and support cells. All of these ingredients are also found in the brain in our heads.  In fact, nearly every substance that helps run and control the brain (in your head) is also found in the gut, including serotonin, dopamine and adrenaline. Plus, like the brain in our heads, the complex circuitry in the ENS allows it to act independently, learn and even remember.

Brainy development

Here is some food for thought (ahem): in foetal development the two nervous systems originally came from the same clump of tissue called the neural crest. When a foetus is developing inside the womb this crest forms very early, and then it splits. One section goes to the head and spine, and becomes the Central Nervous System, and the other section becomes the Enteric Nervous System.  These two systems then become connected when a large nerve, called the vagus nerve, develops between them.

Stress head

When the brain (in our heads) is in a stressful situation it releases stress hormones, such as adrenaline, throughout the body. The lining of the stomach (like our brains) has many adrenaline receptors. When adrenaline surges through our body, it is picked up by the receptors in the stomach. This leads to butterflies and cramps. (This also explains why some  women get period pain… the hormones are going out of control, and the stomach picks up on it.)

Fear also incites the vagus nerve to ramp up its production of serotonin in the gut. This over-stimulation can cause the gut to digest food faster than usual, leading to diarrhea.

The second brain also explains a lot of common phenomena that happen to us when we are stressed or emotional. When people get “all choked up” with emotion it’s often due to nerves in the oesophagus being highly stimulated, leaving people with difficulty swallowing.

Plus, we now know why drugs such as antidepressants can give people a physical reaction like gaining weight, nausea and cramping. Since similar chemicals and receptors for those chemicals are found in the head and gut, when you make a drug to have an effect on the brain, it’s very likely to affect the gut too.

And finally, ever had a gut reaction that you followed for no rational reason at the time, and only afterward realized it made sense? Well, the Enteric Nervous System has a memory, and can learn, so this bunch of nerves in your stomach is probably the answer for this marvel too.

Of course it might be a little hard to swallow, a brain in your stomach, but why not? We tend to plan our lives around our next meal, and our next coffee break. Perhaps it is time that we gave our stomach’s a little more credit.