Enteric Nervous System
Your “gut feeling” might be right. We all have two brains, one in our heads, and one in our guts.
“The enteric nervous system is an independent nervous system embedded in the wall of the gut and is also referred to as the “little brain of the gut”. With 100 million neuronal cell bodies the gut brain containes more nerves than the spinal cord. It is in its true sense an autonomous nervous system which has the capability to control gut functions independent of inputs from the central nervous system. The gut is therefore the only organ which exhibits all vital motor functions and reflexes even when isolated. The capability for autonomous control is due to the fact that the enteric nervous system contains its own set of sensory neurones, interneurones and motorneurones and is functionally and structurally very similar to the brain. In recent years the clinical relevance of the pathophysiology of the enteric nervous system has been recognized and together with continous progress in basic research a new discipline called “Neurogastroenterology” has emerged.”
More reading here.