Plan
► Regulatory mechanisms of gastrointestinal tract. Classification.
► System of hormones of gastrointestinal tract. Classification of gastrointestinal hormones.
► Regulation of secretory activity of stomach as example of regulatory mechanisms of gastrointestinal tract.
► Modern concepts of mechanisms of hunger and satiety.
General Principles of Control of Digestive Process
Functions of the digestive system, coordination of motility, secretion and absorption are regulated by a complex system of neural and humoral mechanisms.
There are three basic mechanisms of regulation of the digestive apparatus: reflex, humoral and local. These mechanisms have different significance in different parts of the gastrointestinal tract. Central reflex mechanisms (both conditioned and unconditioned) are most evident in the upper parts of the gastrointestinal tract. Further down the digestive tract their participation in regulation of digestion progressively decreases, while the role of humoral mechanisms increases and reaches maximum in the stomach, duodenum, pancreas, in regulation of production and excretion of bile. In the small intestine and especially in the large intestine, most significant are the local regulatory mechanisms (mechanical and chemical stimulations).
Food activates secretion and motility of the gastrointestinal tract directly at the site of its action and downstream and inhibits the activity upstream. Afferent impulses from mechano-, chemo-, osmoand thermoreceptors located in the wall of the digestive tract travel to the neurons of intraand extramural ganglia, of the spinal cord and the brain. From there impulses go via the efferent autonomic fibers to the effector cells of digestive organs: glandulo-cytes, myocytes, enterocytes.