h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I'm a grad student over here at the University of Vermont, and had read one of your postings on the vaunted subject of defecation. One thing especially caught my attention - I don't know if you still have the notes or text around - but you'd mentioned that distension of the rectum reduced signalling in afferent neurons, and it was this reduction in signalling accompanying the increase in tension that signalled a certain "urgency," to quote...

"Internal Anal Sphincter

This is innervated by the sympathetic nervous system and the parasympathetic nervous system1, and is 3mm thick, and 3cm long. There are constant messages being sent back from the nerve endings to the central nervous system. The rate at which these signals are sent back, decreases when the rectum distends. Hence one can observe that the greater the mass of stool in the rectum, the more pressure it will exert on the walls of the rectum, and therefore, the more it will distend. The reduction in messages sent to the central nervous system from the anus is what gives the feeling of 'urgency' ie, the feeling that one is required to evacuate one's bowels."

I was wondering if I could look up a reference for that if you had it. It'd be really interesting as an alternative to other mechanosensory systems where they're usually silent, and only signal upon activation. And would make a lot of sense out of some confusing results!
Congratulations on finishing and thanks for the post!
Derek Strong