Physio Gi Hormones13.


Published on

Medical college lectures: physiology 2nd year.

  • Be the first to comment

No Downloads
Total Views
On Slideshare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Physio Gi Hormones13.

  1. 1. Endocrine Control of Gastrointestinal Function Dr.Mohammad Shaikhani
  2. 2. GI Hormones Glucose, AA Fatty acids Duodenum Jejunum Insulin secretion Gastric acid secretion GIP Acid fat Duodenum Pepsin secretion Pancreatic juice secretion enzymes bicarbonate Pancreatic exocirne growth Secretin Peptides, AA Fatty acids>8C Acid Duodenum Jejunum Gall Bladder contraction Pancreatic juice secretion enzyme bicarbonate Pancreatic exocirne growth CCK Peptides, AA Distention Vagal activity Antrum duodenum Gastric acid secretion Growth of oxyntic gland mucosa Gastrin Secretion stimulus Release site Action Hormone
  3. 3. GI Hormones Glucose Fat Ileum unknown Enteroglucagon Protein Fat Glucose Pancreas Pancreatic juice secretion enzyme bicarbonate Pancreatic polypeptide Unknown Duodenum Jejunum Gastric and duodenal motility Motilin Secretion stimulus Release site Action Peptide
  4. 4. Neurocrines Gastric mucosa Muscosa and smooth muscle of GI tract Stimulates gastrin secretion Stimulates smooth muscle contraction Inhibits intestinal secretion Bombesin or GRP Enkephalins Duodenum Jejunum Relaxes sphincters Relaxes gut circular muscle Stimulates intestinal secretion Simulates pancreatic secretion VIP Release site Action Peptide
  5. 6. Activation of pancreatic proteases in small intestine <ul><li>CCK stimulates duodenal mucosal cells to produce enteropeptidase </li></ul>
  6. 7. Hormone secretions of small intestine: CCK <ul><li>Inhibits gastric emptying </li></ul><ul><li>↑ secretion of pancreatic enzymes &HCO 3 - </li></ul><ul><li>Stimulates release of enteropeptidase </li></ul><ul><li>Stimulates gall bladder contractions </li></ul><ul><li>Chyme with a: </li></ul><ul><li>High amino acid </li></ul><ul><li>High fatty acid </li></ul><ul><li>Low pH </li></ul>Primarily duodenal mucosa Actions Stimuli for secretion Site of secretion
  7. 8. CCK: most important stimulus for gall bladder contraction & release of bile into small intestine
  8. 9. Hormone secretions of the small intestine: secretin <ul><li>Inhibits gastric emptying </li></ul><ul><li>↑ secretion of pancreatic enzymes & HCO 3 - </li></ul><ul><li>Stimulates release of enteropeptidase </li></ul><ul><li>Stimulates gall bladder contractions </li></ul><ul><li>↓ HCl production in stomach </li></ul><ul><li>↑ biliary HCO 3 - secretion </li></ul><ul><li>Chyme with a: </li></ul><ul><li>High amino acid concentration </li></ul><ul><li>High fatty acid concentration </li></ul><ul><li>Low pH </li></ul>Primarily duodenal mucosa Actions Stimuli for secretion Site of secretion
  9. 10. Hormone secretions of the small intestine: CCK <ul><li>Cholecystokinin:&quot;move the gallbladder“. </li></ul><ul><li>Cholecystokinin plays a key role in facilitating digestion within the small intestine . </li></ul><ul><li>It is secreted from mucosal epithelial cells in the first segment of the small intestine (duodenum). </li></ul><ul><li>It is also produced by neurons in the enteric nervous system & widely distributed in the brain. </li></ul><ul><li>It stimulates delivery into the small intestine of digestive enzymes from the pancreas & bile from the gallbladder . </li></ul><ul><li>The most potent stimuli for secretion of cholecystokinin are the presence of partially-digested fats & proteins in the lumen of the duodenum. </li></ul><ul><li>Disease States </li></ul><ul><li>Cholecystokinin deficiency causes malabsorption similar to pancreatic exocrine insufficiency. </li></ul><ul><li>In the human brain causes certain types of anxiety & schizophrenia. </li></ul>
  10. 11. Hormone secretions of the small intestine: Gastrin <ul><li>It is a major physiological regulator of gastric acid secretion </li></ul><ul><li>An important growth-promoting influence on the gastric mucosa. </li></ul><ul><li>Gastrin is synthesized in G cells, in the antrum of the stomach , binds receptors found predominantly on parietal & enterochromaffin -like cells . </li></ul><ul><li>Control and Physiologic Effects of Gastrin </li></ul><ul><li>The primary stimulus for secretion of gastrin is the presence of certain foods, especially peptides, certain amino acids &calcium, in the gastric lumen&unidentified compounds in coffee, wine, beer. </li></ul><ul><li>Secretion of this hormone is inhibited when the lumenal pH of the stomach becomes very low (< 3). </li></ul><ul><li>Disease States </li></ul><ul><li>Excessive secretion of gastrin, or hypergastrinemia, Occur in Zollinger-Ellison syndrome, result of gastrin-secreting tumors (gastrinomas), which develop in the pancreas or duodenum with excessive &unregulated secretion of gastric acid causing intractable peptic ulceration. </li></ul>
  11. 12. Hormone secretions of the small intestine: secretin <ul><li>Secretin functions as a type of fireman: </li></ul><ul><li>it is released in response to acid in the small intestine& stimulates the pancreas to release of bicarbonate, which neutralizes the acid. </li></ul><ul><li>A similar, but less important response to secretin is bile duct cells , resulting in additional bicarbonate releases& pumped into the SI. </li></ul>
  12. 13. Hormone secretions of the small intestine: VIP <ul><li>VIP is very widely distributed in the peripheral & central nervous systems, & GI. </li></ul><ul><li>VIP induce smooth muscle relaxation (lower esophageal sphincter, stomach, gallbladder). </li></ul><ul><li>Stimulate secretion of water into pancreatic juice & bile& cause inhibition of gastric acid secretion & absorption from the intestinal lumen. </li></ul><ul><li>Certain tumors from the pancreatic islets or nervous tissue (called VIPomas) secrete excessive quantities of VIP& are associated with chronic, watery diarrhea. </li></ul>
  13. 14. Hormone secretions of the small intestine: Motilin <ul><li>Motilin secreted by endocrinocytes in the mucosa of the proximal small intestine. </li></ul><ul><li>Motilin controls smooth muscle contractions in the upper GIT. </li></ul><ul><li>Motilin is secreted into the circulation during the fasted state & sweep the stomach &small intestine clear of undigested material ( migrating motor complex ). </li></ul><ul><li>An alkaline pH in the duodenum stimulates its release. </li></ul><ul><li>Erythromycin & related antibiotics act as nonpeptide motilin agonists& used for their ability to stimulate GIT motility. </li></ul>
  14. 15. Hormone secretions of the small intestine: GIP <ul><li>Gastric inhibitory peptide (GIP) </li></ul><ul><li>or Glucagon-Like peptide(GLP) </li></ul><ul><li>Or glucose-dependant insulinotropic peptide </li></ul><ul><li>Is a member of the secretin family of hormones. </li></ul><ul><li>Inhibited gastric motility &secretion of acid, initially called enterogastrone . </li></ul><ul><li>Like secretin, it is secreted from mucosal epithelial cells in the first part of the small intestine. </li></ul><ul><li>Enhance the release of insulin in response to infusions of glucose ( glucose-dependent insulinotropic peptide ) </li></ul><ul><li>Used as a base for treating diabetes melitus. </li></ul>
  15. 16. GLP-1: effects in humans GLP-1 is secreted from L-cells of the jejunum and ileum That in turn… <ul><li>Stimulates glucose- dependent insulin secretion </li></ul><ul><li>Suppresses glucagon secretion </li></ul><ul><li>Slows gastric emptying </li></ul>Long-term effects in animal models: <ul><li>Increase of β -cell mass and improved β -cell function </li></ul><ul><li>Improves insulin sensitivity </li></ul><ul><li>Leads to a reduction of food intake </li></ul>Drucker. Curr Pharm Des. 2001 Drucker. Mol Endocrinol . 2003 After food ingestion…
  16. 17. Hormone secretions of the SI : Ghrelin <ul><li>Ghrelin peptide hormone stimulates release of growth hormone from the anterior pituitary. </li></ul><ul><li>Along with several other hormones, has significant effects on appetite and energy balance. </li></ul><ul><li>The predominant source of ghrelin is epithelial cells in the stomach. </li></ul><ul><li>Also present on the cells in the pituitary that secrete growth hormone & in the hypothalamus, heart& adipose tissue . </li></ul>