If you want to bone up on the enteric nervous system, the system controlling all the goings on in your gut, then this is the place.

The nervous system in your gut is almost as complex as your brain. Amazingly the gut can (if necessary) work on its own, without any connections to your brain. Because is so similar in terms of structure, we are sometimes offered anti-depressants to deal with the symptoms of IBS. That also may be why hypnotherapy is so useful.