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DESCRIPTIONPANCREATIC HORMONES. Dr.Mohammed Sharique Ahmed Quadri Assistant professor Almaarefa College. Objectives. Describe the functional anatomy of the pancreas List all pancreatic hormones Describe the regulation of pancreatic hormone secretions - PowerPoint PPT Presentation
Endocrine Control of Fuel Metabolism
1PANCREATIC HORMONES Dr.Mohammed Sharique Ahmed QuadriAssistant professorAlmaarefa College 2ObjectivesDescribe the functional anatomy of the pancreas
List all pancreatic hormones
Describe the regulation of pancreatic hormone secretions
Illustrate the mechanisms of action of insulin and glucagon
Discuss the physiological effects of insulin and glucagon3Interconversions Among Organic MoleculesFood intake is intermittent nutrients must be stored for use between mealsExcess circulating glucoseStored in liver and muscle as glycogenOnce liver and muscle stores are filled up, additional glucose is transformed into fatty acids and glycerol and stored in adipose tissueExcess circulating fatty acidsBecome incorporated into triglyceridesExcess circulating amino acidsConverted to glucose and fatty acids
4Stored Metabolic Fuel in the Body
5Comparison of Absorptive and Postabsorptive StatesAbsorptive stateFed stateGlucose is plentiful and serves as major energy sourcePostabsorptive stateFasting stateEndogenous energy stores are mobilized to provide energy
6Roles of Key Tissues in Metabolic StatesLiverPrimary role in maintaining normal blood glucose levelsPrincipal site for metabolic interconversions such as gluconeogenesisAdipose tissuePrimary energy storage siteImportant in regulating fatty acid levels in the bloodMuscle Primary site of amino acid storageMajor energy userBrainNormally can only use glucose as an energy source Does not store glycogenMandatory blood glucose levels be maintained 7Pacreas
8Endocrine Pancreas 1-2 million islets are present.
Each is richly supplied by blood that finally drains in to the Portal Vein.
9The Endocrine Pancreas (Islets of Langerhans)
Beta (B cells)60-70% of islet cellsInsulinAlpha (A cells)20 -25% of islet cellsGlucagon
Delta (D cells)10% of islet cellsSomatostatin
F (PP) cellsApprox 1% of islet cellsPancreatic polypeptideInsulin and glucagon areMost important in regulating fuel metabolism
10Pancreatic HormonesInsulinAnabolic hormonePromotes cellular uptake of glucose, fatty acids, and amino acids and enhances their conversion into glycogen, triglycerides, and proteins, respectivelyLowers blood concentration of these small organic moleculesSecretion is increased during absorptive statePrimary stimulus for secretion is increase in blood glucose concentration
11Glucose Levels and Insulin Release from the Beta Cells
Short half life (3-6 min)12The Insulin Receptor
Membrane glycoproteins composed of 2 subunits
sub unit has Tyrosine kinase activity
Sequence of events:Binding of insulin to site unit trigger the autophosphorylation of tyrosine kinase of sub unit. Thus insulin exerts its biological action.
Factors affecting blood glucose
14ACTIONS OF INSULIN1.CARBOHYDRATE METABOLISM
: Promotes glucose uptake & storage:Promote glycogenesis( synthesis of glycogen from glucose) Increases activity of Glycogen Synthetase Inhibits Glycogenolysis( breakdown of glycogen into glucose) Inactivates liver Phosphorylase thus in liver. Inhibits Gluconeogenesis by( Conversion of AA into glucose)decreasing the activity of liver enzymes necessary for gluconeogenesis.Increases activity of Glucokinase. This causes initial phosphorylation of glucose after it diffuses into the cells.Therefore net effect isTo increase glycogen synthesis in liver.To decrease glucose in blood
1.CARBOHYDRATE METABOLISM Muscle It increases glucose entry by increasing GLUT4. Increases storage of glycogen Adipose tissue Promotes glucose entry [GLUT4.] which is then used to form glycerol phosphate.
This provides the glycerol which combines with fatty acids to form triglycerides thus promoting deposition of fat.
Glucose Transporters RecruitmentInsulin increases glucose uptake in most of the cells by GLUT4 ( glucose transporters)
GLUT4 operates only after binding with insuline.
In insuline dependent cells GLUT4 are retrieved from plasma membrane when insulin secretion decreases
17Tissue that do not depend on insuline for glucose uptake BRAIN
LIVER 18Action of insulin on PROTEIN METABOLISM insulin decreases blood amino acid level & stimulate protein synthesis.
Promotes active transport of A.A in muscles and other tissue s
Stimulates protein synthesis in cell
Inhibits protein breakdown
Action of insuline on FAT METABOLISM Decrease blood fatty acid level & promotes Triglyceride storage Promotes entry of FA into adipose tissue cells Promotes entry of glucose into adipose tissue cells- precursors for FA & glycerol, raw material for synthesis of Triglycerides Promotes synthesis of TG from FA and glycerolInhibits lipolysis hence release of FA from adipose tissue 20Other Effects of insuline Helps in general growth along with other hormones.
2. On electrolytes causes increased entry of K+ into cells thereby decreasing plasma K+ levels.
Factors controlling insuline secretion
23Pancreatic HormonesGlucagonMobilizes energy-rich molecules from storage sites during postabsorptive stateSecreted in response to a direct effect of a fall in blood glucose on pancreatic cellsGenerally opposes actions of insulinGlucagon is the hormone of "starvation." - It produces hyperglycemia24Blood Glucose and the Pancreatic Hormones
25Actions of Glucagon ON CARBOHYDRATE:Stimulates hepatic glycogenolysis.Increases gluconeogenesis.ON FAT: Promotes fat breakdown and inhibits triglyceride syntheis - FFA and glycerol in blood -used for gluconeogenesis - Oxidation for energy (Ketogenesis) ON PROTEIN:Inhibits protein synthesis - Proteolytic Effects
Glycogenolytic, Gluconeogenic, Lipolytic, Ketogenic Hormone.
COMPLEMENTARY INTERACTION OF GLUCOSE AND INSULINE
Counteracting action of insulin & gluccagon during absorption of high protein 28SomatostatinReleased from pancreatic D cells in direct response to increase in blood sugar and blood amino acids during absorption of a mealInhibitory effect on both insulin and glucagonDecreases motility of stomach, duodenum and gallbladderDecreases secretion and absorption in the gastrointestinal tract
End resultInhibits digetion and absorption of nutrientsDecreased utilization of absorbed nutrients by tissuesExtends the availability of nutrients for longer periods of time
ReferencesHuman physiology by Lauralee Sherwood, seventh editionText book physiology by Guyton &Hall,11th editionText book of physiology by Linda .s contanzo,third edition