Brain and Neural
The phrases "gut feeling" or "going with your gut" have some practical science behind them. It's because of the Enteric Nervous System in each of us, and its control over our bodies and brains. So powerful is this neural control center, it's been nicknamed "the second brain."
The Second Brain
Most of us think of our nervous system as just the brain, spinal cord and our nerves. Which is right, but not the complete story. Connected to the brain, but operating independently, the enteric nervous system or ENS is comprised of about 100 million neurons. While substantial, that's still only about same number of neurons in the spinal cord and 1/1000 the neurons in the brain.
The ENS controls the gastronintestinal system and is part of the autonomic nervous system responsible for digestive contractions called peristalsis, secretion of enzymes and communication via neurotransmitters. The science of this region is called neurogastroenterology. Your gut is where about 90% of your serotonin and 50% of your dopamine reside, so the ENS plays an important part not just in digestive control, but in your general health, sleep, mood, aggression and emotions.