tailieunhanh - Ebook Usmle road map physiology: Part 2

(BQ) Part 2 book "Usmle road map physiology" presents the following contents: Gastrointestinal physiology, endocrine physiology, neurophysiology. Invite you to consult. | GASTROINTESTINAL PHYSIOLOGY I. Regulation Muscle Nerves and Hormones of the Gut A. Muscles of the gut deal with movement and mechanical processing of luminal contents moving mixing and storing ingested food. B. Voluntary muscle is located at the upper mouth pharynx and first third of the esophagus and lower external anal sphincter gastrointestinal GI tract. C. Smooth muscle structures have a nervous system of their own that can function without any extrinsic innervation Figure 5-1 . D. This enteric nervous system coordinates all activities and consists of the myenteric plexus between the longitudinal and circular muscle layers and the submucosal plexus between the circular muscle and muscularis mucosa. 1. Receptors in the wall of the gut may be chemoreceptors that respond to chemicals such as hydrogen ions or mechanoreceptors that respond to stretch or tension. 2. Efferent fibers connect with muscles to cause contraction with endocrine cells to release peptides and with secretory cells to release secretions. a. The mucosa of the gastric antrum and the small intestine contains primarily endocrine cells. b. There are four major regulatory peptides in the gut 1 Gastrin is released from the gastric antrum G cells by stomach distention vagal innervation and protein digestive products. It stimulates gastric secretion motility and mucosal growth. 2 Cholecystokinin CCK is released by duodenal I cells stimulated by fat and amino acids. CCK stimulates pancreatic enzyme secretion and contraction of the gallbladder primarily. 3 Secretin is released by acid from the S cells of the duodenum. It stimulates HCOj- secretion from the pancreas and liver and inhibits gastric motility and secretion. 4 Gastric inhibitory peptide or glucose insulinotropic peptide GIP is released by dietary fat carbohydrate and amino acids from duodenal cells . It stimulates insulin release and inhibits gastric motility and secretion. E. Although the whole system can function without extrinsic innervation