Intestinal Hormones Inhibit
1QUIZ/TEST REVIEW NOTESSECTION 3 INTESTINAL PHASE OF DIGESTIONDIGESTIVE SYSTEM CHAPTER 21I.INTESTINAL PHASE AND FEEDBACK SIGNALSa. Intro Net result of gastric phase isoooDigestion of proteins in the stomach by pepsinFormation of chime by action of pepsin, acid andperistaltic contractionsControlled entry of chyme into the small intestineLearning Objectives: Describe processes of digestion,absoprotion, motility andsecretion in intestine/colon Neuroendocrine controls ofintestinal phase of digestion Digestive processes ofcarbohydrates, fats, and proteins Role of bicarbonate throughoutdigestion Summarize function of pancreaticenzymes and specific functions ofthe brush boarder disaccaridases Explain significance of waterabsorption and motility in colonb. Slowing of feedforward and positive feedback escalation of gastric function1.2.Positive Feedback of gastric phase to regulate delivery rate of chyme from thestomachFeedforward to promote digestion, motility and utilization of nutrientsc. Intestinal HormonesIntestinal Hormones Inhibit: Gastric Secretion and MotilityIntestinal Hormones Promote: Intestinal Digestion and Glucose AssimilationSecretin HormoneChyme/Stimulus For Release:Secreted By:(-) Negative Effect (Inhibitory):( ) Positive Effect (Excitatory):Targets:Inhibitor:AcidDuodenumGastric secretion and motilityPancreatic BicarbonatePancreas and StomachSomatostatinGIP Hormone (Gastric InhibitoryPeptide)Chyme/Stimulus For Release:Secreted By:(-) Negative Effect (Inhibitory):( ) Positive Effect Gastric SecretionPancreatic Insulinβ-cells of pancreasCCK Hormone (Cholecystokinin)Chyme/Stimulus For Release:Secreted By:(-) Negative Effect (Inhibitory):( ) Positive Effect (Excitatory):Targets:Fats and ProteinsDuodenum (also brain)Gastric Secretion and MotilityPancreatic EnzymesGall bladder, pancreas, gastric smoothmuscleInsulin release is afeedforwardmechanism/response inanticipation of high levels ofsugarCCK enhances Satiety, thefeeling that hunger has beensatisfied
2d. Intestinal Osmoreceptors Mixture of acid, enzymes, and digested chyme forms a hyperosmotic solution Osmoreceptors in intestine walls of lumen are sensitive to osmolarity of entering chyme When stimulated by high osmolarity the receptors inhibit gastric emptying in a reflex mediatedby unknown blood-borne substanceII.SMALL INTESTINAL DIGESTIONa. Pancreatic duct cells release bicarbonate to neutralize the acidic chymeoooBicarbonate secretion into the small intestine neutralizes highly acidic chymeentering the stomachMost bicarbonate comes from the pancreas and is released in response to neuralstimuli and secretinSignals for pancreatic enzyme release: Food in the intestine Neural signals Hormone CCKb. Bicarbonate SecretionooSmall amount of bicarbonate comes from duodenal cells and the rest comes from thepancreas which secretes NaHCO3Exocrine Function Duct Cells (Secrete Bicarbonate; NaHCO3) Acinar Cells (Secrete Digestive Enzymes)Enzyme Optimal pH:Gastric Enzymes: AcidophilesIntestinal Enzymes: Alkalophiles
3ooooBicarbonate production requires high levels of carbonic anhydraseBicarbonate produced by CO2 and H2O is secreted by Cl--HCO3- anti-port proteinsChloride (Cl-) influx by NKCC cotransporter and efflux by CFTR channelHydrogen ions produced along with bicarbonate leave cell by Na -H anti-portCystic Fibrosis: Inherited defect causesthe CFTR channel to be defective orabsent. Result: Secretion of chloride andfluid ceases, but goblet cells continue tosecrete mucus, resulting in thickenedmucus- In the G.I. the mucus clogs smallpancreatic ducts and preventsdigestive enzyme secretion intointestine- In Respiratory system, the CFTRchannel failure to secrete fluidclogs the mucociliary escalator,leading to lung infectionsc. NaCl SecretionoooIn addition to ion secretion bypancreas, crypt cells in smallintestine/colon secrete NaClsolutionActive step is Cl- secretionwhich is followed by Na andH2O secretionSecreted saline solution withmucus secreted by goblet cellshelps to lubricate contents ofgut
4d. Pancreatic Acinar-cell Digestive Enzymes that have neutral pH OptimumPANCREATIC AMYLASEPANCREATIC LIPASE AND COLIPASETRYPSIN AND CHYMOTRYPSINPHOSPHOLIPASEBreakdown Glycogen and Starch to Maltose;(All intestinal carbohydrate transport is restricted tomonosaccharide’s)Breakdown Fats to Monoglycerides and Free FattyAcidsBreakdown proteins (Endopeptidases: Attack peptidebonds and activated by GI tract lumen; when firstreleased from Pancreas they inactive proenzymes)Breakdown Phospholipidse. Brush Boarder EnzymesoCreated by epithelia cells on apical surface of a Intestinal Villus; consists ofMicrovillus
5f. Addition of bile from the liver and gall bladdera. Bile compositiono Is a nonenzymatic solution secreted from hepatocytes/liver cells and isstored in the gallbladder of the livero Key componentsBilirubin A bile pigment that isthe waste product ofhemoglobindegradationBile salts Act as detergents tosolubilize fats duringdigestion Made from steroid bileacids combinged withamino acidsCholesterol Excreted in the fecesBILE SALTS CONTINUED BILE SALTS FACILITATE FAT DIGESTION Bile salts interact with lipids to break down coarse emulsion into smaller, more stableparticles Bile salts are amphipathic (polar/non-polar) containing hydrophobic and hydrophilic regionso Hydrophobic: associates with surface of lipid dropletso Hydrophilic: associates with water, creating stable emulsion of small water-solublefat droplets Bile salt coating of emulsion fat prevents pancreatic lipase penetration, so colipase is neededo Colipase Secreted from pancreas Displaces some bile salts allowing some lipase to access fat inside bilecoating Creation of micelles where final stages of fat catabolism occur
6III.ABSORPTIONa. StomachooLipid-soluble substancesAlcohol and Drugsb. Small Intestineo90% of all nutrients Peptides Amino Acids Glucose Fructose Fats Water Ions Minerals VitaminsoWater Absorption (primary) ALSO Ions Minerals Vitamins Small organic molecules produced by bacteriac. Colon
o Controlled entry of chyme into the small intestine b. Slowing of feedforward and positive feedback escalation of gastric function 1. Positive Feedback of gastric phase to regulate delivery rate of chyme from the stomach 2. Feedforward to promote digestion, motility and utiliza
order to maintain a state of stability or homeostasis. Some endocrine glands secrete hormones in response to other hormones. The hormones that cause secretion of other hormones are called tropic hormones. A hormone from gland A causes gland B to secrete its hormone. A third meth-od of regulating hormone secretion is by direct nervous stimulation.
hormones on the body. The release of hormones is necessary both for day-to-day body functions and for the growth and development of the human body. In this unit, students will consider the endocrine system, the hormones released, and the hormones' role in human growth and development. Depending on the phase of life, the endocrine system will
tinal microbiota. Changes in the dietary structure lead to the occurrence and development of metabolic diseases by affect-ing the composition and function of intestinal microbiota. For example, alterations in intestinal microbiota inhibit the transformation of bile acid in the lipid and glucose metabo-lism disturbance induced by a high-fat .
Other protozoal intestinal diseases (007) Balantidiasis (007.0) Giardiasis (007.1) Coccidiosis (007.2) Intestinal trichomoniasis (007.3) Other protozoal intestinal diseases (007.8) Unspecified (007.9) Intestinal infections due to other organisms (008) Escherichia coli (008.0) Arizona (008.1) Aerobacter aerogenes (008.2)
Other protozoal intestinal diseases (007) Balantidiasis (007.0) Giardiasis (007.1) Coccidiosis (007.2) Intestinal trichomoniasis (007.3) Other protozoal intestinal diseases (007.8) Unspecified (007.9) Intestinal infections due to other organisms (008) Escherichia coli (008.0) Arizona (008.1) Aerobacter aerogenes (008.2)
disrupt intestinal microbiota community, alter inflam-matory cytokines, decrease luminal SCFAs, and disrupt intestinal epithelial barrier. Thus, it is suggested that intestinal microbiota dysbiosis may contribute to the barrier dysfunction following a severe burn. Methods Animals Healthy adult female C57BL/6 mice weighing 18-22g were used in .
Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2). Slide 1 Hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary. In resp
2. Glands and hormones make a great team. Describe how they work in the body. How do they work with other body systems? 3. Hormones are extremely specific. What does this mean? Describe the process by which hormones reach their intended targets. 4. The endocrine system produces hormones, and it also senses when to shut them off.
