The effect of diet on small intestinal and biliary tract function.

During fasting, the motor and secretory activity of the small intestine and biliary tract is characterized by periodic oscillation between activity and quiescence. On fasting, motor and secretory activity is continuous although variable. Different phases of activity are marked by variations in plasma levels of gastrointestinal regulatory peptides, but current evidence indicates that the interdigestive periodicity is generated in the intrinsic innervation, while the response to food is mediated by vagal sensory receptors. It is now clear that the extent and complexity of neurochemical regulation of gut function by both the enteric and central nervous systems has been hitherto underestimated.