Our
relationships help shape our physiology.
The
nervous system of the gut contains about one hundred million nerve cells --- we
have as many in the small intestine alone as there are in our entire
spine! These nerves do more than
coordinate the digestion and absorption of food and the elimination of waste
--- they also form part of our sensory apparatus. The gut responds to emotional
stimuli by muscle contractions, blood flow changes and the secretion of a
multitude of biologically active substances. Such brain-gut integration is
essential for survival. In turn, the gut
is abundantly supplied with sensory nerves that carry information to the
brain. Quite to the contrary of what was
believed until recently, nerve fibres ascending from the intestines to the
brain greatly outnumber ones descending from brain to gut.
