elements into the body, and taking waste product out of it. Proper functioning of this system depends on an unobstructed and regulated flow of these elements. In addition to the structure of this tube, there are accessory organs (liver, gall bladder, salivary glands, and pancreas)that aid the digestive tract through the production or secretion of enzymes that help in the digestion of food products.
Flow of material along the gastrointestinal tract occurs by peristalsis, a wavelike contraction of longitudinal and circular muscle fiber that moves food through the gut. Another process occurring in the gastrointestinal tract is segmentation: periodic,repeating intestinal constrictions that cause churning of the GI content (figure 11-2).Regulations of these action is controlled by many mechanisms. One control mechanism of the GI tract is the autonomic nervous system (ANS),which consists of the sympathetic branch fight-or-flight response )and the parasympathetic branch (homeostatic response ).Parasympathetic stimulation increase intestinal motility, increase GI secretion, and relaxes sphincter. Cholinergic drugs simulate these action. Anticholinergic drugs inhibit these action. Sympathetic stimulation decrease intestinal motility, decrease intestinal secretion, and inhibit the action of sphincter. Sympathetic drugs simulate these action. Stretch receptor in the GI tract also increase peristalsis. Chemical secretion also control the GI tract. Hormone release from the intestinal cell help control action such as gall bladder emptying. Chemical substance such as histamine can attach to the H2 receptor of the gastric cell, causing increased HCl production