Digestive Phys and Glucose Metabolism Flashcards
Gastrin
secreted by stomach
The presence of food in the stomach stimulates secretion of the gastrin into the circulatory system.
Gastrin in-turn stimulates the secretion of gastric juice in the stomach.
Secretin
secreted by duodenal cells.
Secretin secretion is stimulated by acid chyme (food from stomach).
Secretin stimulates the pancreas to secrete sodium bicarbonate, which neutralizes the acidic chyme.
Secretin also stimulates the liver to release bile.
CCK
secreted by the small intestine (mainly duodenum & jejunum).
CCK secretion is stimulating by the food present in the small intestine.
It stimulates the gallbladder to release bile and the pancreas to produce pancreatic enzymes.
GIP (Gastric Inhibitory Peptide)
secreted by the duodenum
GIP secretion is stimulating by the food in the duodenum.
It counteracts the effects of gastrin that is it inhibits gastric glands. Furthermore, slow down stomach emptying if there is food in the duodenum.
Motilin
Motilin is in the duodenum, increases the migrating myoelectric complex component of gastrointestinal motility, and stimulates the production of pepsin.
Ghrelin
produced in the stomach and upper part of the intestine in the absence of food stimulates appetite.
act in coordination with the brain to help regulate the intake of food for energy.
Peptide YY
synthesized in the digestive tract in response to food and inhibits appetite
act in coordination with the brain to help regulate the intake of food for energy.
Islets of Langerhans Four major cell types
Alpha (A) cells secrete glucagon
Beta (B) cells secrete insulin
Delta (D) cells secrete somatostatin
F cells (Gamma) secrete pancreatic polypeptide
Alpha Cells
Release Glucagon; main action to produce an increase in blood glucose:
Breakdown of glycogen
Stimulates gluconeogenesis
Increases transport of AA into the liver and stimulates their conversion to glucose
High levels activate adipose cell lipase making fatty acids available for use as energy
Released into portal circulation in response to low glucose levels in blood, stimulated by high concentrations of AA and by strenuous exercise
Beta Cells
Produce insulin—lowers blood glucose by:
Promoting uptake of glucose by target cells*
Provides for glucose storage as glycogen
Prevents fat & glycogen breakdown
Inhibits gluconeogenesis and increases protein synthesis
Promotes fat storage by increasing transport of glucose into fat cells
Increases triglyceride synthesis
Beta cells produce pro-insulin
Insulin
Insulin directly enters the portal venous circulation before the peripheral circulation
Major regulator of insulin is glucose
In pancreatic beta cell glucose transporters allow influx of glucose: glucokinase
Results in closure of K+ channels and opening of Ca+ channels allowing secretion of insulin by exocytosis
Delta Cells
Secrete prosomatostatin that is processed to somatostatin-14 and somatostain-28
Actions:
Inhibits secretion of growth hormone and thyro-tropin from pituitary
Inhibits insulin and glucagon in the endocrine pancreas
Inhibits gastrin release and gastric acid secretion from parietal cells
Inhibits exocrine secretion of pancreas
Signs and Symptoms of Hypoglycemia
Sweating, Palpitations, Tremor, Nervousness, Irritability, Paresthesias, Hunger, Nausea/vomiting
Headache, Tired and drowsy, Dizzy and fainting, Blurred vision, Confusion, Abnormal behavior, Seizures, Coma
Whipple’s Triad
Grouping of symptoms consistent with hypoglycemia
Low plasma glucose (< 55 mg/dL)
Relief of symptoms by raising plasma glucose
Type I DM (IDDM)
autoimmune destruction of -cells
insulinopenia
ketonemia
dependent on insulin to sustain life and prevent ketoacidosis
