Gastrointestinal Hormones
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28 terms
Terms | Definitions |
|---|---|
 Gastrointestinal Hormones, Gland:Producing cells located from the stomach to the colon, Not grouped into | distinct glands Distributed, often individually, throughout GI epithelium |
| Gastrointestinal Hormones, Gland: Cell subtypes have specific distribution patterns, Some distributed evenly Others localized | to a specific region(s) |
| Hormones released in response to the presence of food Scattered distribution of the cells may allow better response to | stimulus |
| Gastrointestinal Hormones Producing cells are | enteroendocrine (enterochromaffin or enterochromaffin-like (ECL)) cells |
| Secretory granules are at the base of the cells - suggesting release of products into the | extracellular space below (tissue side) rather than apical into lumen of gut |
| Gastrointestinal Hormones, Gland "enteroendocrine (enterochromaffin or enterochromaffin-like (ECL)) cells" These, and related cells in other systems, sometimes referred to as the "Diffuse Neuroendocrine System" Have endocrine function | Derived from embryonic nervous system Widespread Approximately 35 cell types; includes respiratory, urinary, and G.I. systems Many of their signaling molecules have both neural and endocrine function Typically found in between non-endocrine epithelial cells |
| Altogether, the endocrine cells of the mucosal layer of the gastrointestinal tract may be considered to be the largest | endocrine gland in the body |
| Gastrointestinal Hormones, Gland: Isolated cell distribution makes the initial characterization of these cells and the hormones they produce | difficult |
| Digestive system function is controlled by the nervous system, but modulated by | locally produced hormones |
| Hormones produced by cells in the digestive tract function to promote | the various digestive processes |
| In 1905, J.S. Edkins describes effect of gastric mucosal extracts on acidification of stomach contents | a "Gastric Secretin" he called Gastrin As Edkins found, this hormone is produced by enteroendocrine G cells in the pyloric region, but not in other parts of the gastric mucosa |
| Hormones: Some grouped into two families based upon shared amino acid sequences: Gastrin family consisting of the | Gastrins and Cholecystokinin |
| Secretin family consisting of | Secretin, Glucagon, Glucagon-like Polypeptides, Vasoactive Intestinal Polypeptide, Gastric Inhibitory Peptide |
| Gastrin: | a polypeptide with several forms At least 3 forms circulate in most mammals Major form of 34 aa; also forms of 95 aa, 17 aa, and 14 aa All share 5 aa's @ the amino terminus with cholecystokinin = "pentagastrin" Sulfation near amino terminus important for activity |
| Gastrins Component | Component I = Big Big = 95 aa's, Probably a preprohormone, does not circulate Component II = Big = 34 aa's, hormonal form, probably a prohormone for the smaller forms, circulates Component III = Little = 17 aa's, circulates, hormonal form secreted by some cells Component IV = Mini = 14 aa's, circulates, may be a degradative fragment |
| Cholecystokinin: | 33 / 39 aa polypeptide is primary form Shares 5 aa pentagastrin sequence @ amino terminus + 3 more aa within the molecule with gastrin Sulfation near the amino terminus is required for activity |
| Secretin: | 27 aa polypeptide Produced in the duodenum and jejunum Released in response to the arrival of acidic material in the duodenum |
| Gastric Inhibitory Peptide | 43 aa polypeptide Found in the small intestine |
| Ghrelin | 28 aa polypeptide Produced in the stomach |
| Function General These hormones are secreted in response to food; function in promoting | the digestion and movement of food throughout the G.I. tract |
| Gastrin, Primary:Function | Stomach: Stimulates acid production a. Causes the release of histamine near the parietal cells of the stomach mucosa b. Histamine causes parietal cells to secrete Hydrochloric Acid 2. Stomach: Stimulates pepsinogen secretion by the chief cells of the stomach via HCl 3. Stomach: Stimulates growth of the gastric mucosa (stomach & intestine) via release of EGF 4. Gut: Stimulates smooth muscle contraction Gall bladder: Stimulates contraction Pancreas: Stimulates secretions: Pancreatic juice = enzymes, bicarbonate Insulin Glucagon |
| Cholecystokinin: function | 1. Primary: Gall Bladder: Stimulates contraction (Name) Additonal: 2. Stomach: Stimulates contraction of the antrum (near pyloric end) 3. Liver: Stimulates bile production 4. Pancreas: Stimulates secretions Pancreatic juice (Indirect in human) Insulin Glucagon Stimulates growth of acinar cells 5. Intestine: Contraction of smooth muscle Stimulates secretion of mucus (Brunner's glands) Gastrointestinal Hormones Secretin: Primary: Pancreas: Stimulates the release of bicarbonate Potentiates the cholecystokinin stimulated release of enzymes |
| Gastric Inhibitory peptide: function | Pancreas: Stimulates the release of insulin (via glucose) Intestine: Inhibits secretion of gastrin by the mucosa (inhibiting gastric acid secretion) Stimulates healing of the mucosa Stimulates electrolyte and fluid secretions Stimulates mucus secretions from duodenal glands of Brunner |
| Ghrelin: function | Stimulates release of Growth Hormone and other hormones from the anterior pituitary Regulates feeding behavior by modulating expression levels of orexigenic (appetite stimulating) peptides in the hypothalamus. May function in the coordination of energy balance and weight regulation, and its dysregulation may be important in obesity. Has several other physiologic actions besides potential regulation of food intake May also function in sleep Gastrointestinal Hormones Regulation General: Secretion regulated by the presence of food in the gut |
| Gastrointestinal Hormones Regulation Stimulating secretion: Protein, Amino acids, Fatty acids, Ca++, Acidic pH E.g.: | Cholecystokinin levels rise in response to a meal, and drop when food moves further on |
| Innervation (Vagus - Autonomic) Inhibiting secretion (Negative): | Acidity in the stomach |
| Other hormones: | Secretin, Vasoactive intestinal peptide, Gastric Inhibitory Peptide |
| Other GI Hormones:All are peptides; Many are found both in the GI tract and in the central nervous system | Motilin Vasoactive Intestinal Peptide Substance P Gastrin Releasing Peptide Neurotensin Peptide YY Pancreatic Polypeptide Enkephalins Somatostatin |
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