The endorphins are so new that they do not yet have a physiologic classification. The endorphin system may represent a new division of the autonomic nervour system. Endorphins have been discovered throughout the body in the brain, spinal cord, and the enteric system (gastrointestinal tract). The enteric tract, which is responsible for the internal regulartion of the stomach and intestines, is considered by some researchers to be s third branch of the autonomic nervour system. This may expain why people feel their emotion in their gut.