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 nervous 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 regulation of the stomach and intertines, is considered by some researchers to be a third branch of the autonomic nervous system. This may explain why people feel their emotions in their gut.