S7 Pancreas Flashcards
(38 cards)
Where is the pancreas located?
Behind the stomach, on the left side of abdomen, with the duodenum on the right
What part of the gut does the pancreas develop from? And what is it’s blood supply?
The foregut
Coeliac trunk artery
What are the two main functions of the pancreas? Which is the major function?
- exocrine - produces digestive enzymes that are secreted into the duodenum
- endocrine - hormone production
Exocrine
What 7 polypeptide hormones are secreted by the pancreas?
- insulin
- glucagon
- somatostatin
- pancreatic polypeptide (PP)
- ghrelin
- gastrin
- vasoactive intestinal peptide (VIP)
What cells secrete insulin and glucagon?
Beta cells and alpha cells
Which cells secrete somatostatin, PP, ghrelin and gastrin?
Delta cells, PP cells, e cells, G cells
What are the target tissues of insulin?
Liver, adipose and skeletal muscle
What are the target tissues of glucagon?
Liver and adipose
Which metabolic reactions do insulin and glucagon effect?
Insulin - carbs, lipids, proteins
Glucagon - carbs and lipids
Insulin and glucagon are either anabolic or catabolic, which is which?
Insulin - anabolic
Glucagon - catabolic
What is the normal plasma glucose range?
3.3-6mmol/L (UHL reference range)
What is the renal threshold for plasma glucose level? What occurs if this is reached?
10mmol/L then glycosuria occurs (glucose in urine)
Are insulin and glucagon water or lipid soluble? How does this mean it’s transported in the blood?
Water soluble
It dissolves in the plasma (no need for transport proteins)
What is the half life of insulin ad glucagon?
5 minutes
What is margination?
Movement of storage vesicles to the cell surface
What is exocytosis?
Fusion of vesicle with plasma membrane, releasing vesicle products out of cell
How is insulin synthesised in beta cells?
- Pre-proinsulin is translated, signal cleavage occurs, proinuslin is folded (at rough ER)
- Proinsulin is transported to the Golgi
- Proinsulin is cleaved to produce insulin and C-peptide
What is the structure of insulin?
A peptide with an alpha helix structure
- two unbranched peptide chains, c-peptide between them
- 3 disulphide bonds (increase stability of insulin)
What are K(ATP) channels?
Channels in pancreatic beta cells that are sensitive to ATP - a high ATP concentration closes these channels, higher AMP opens them
How does glucose stimulate insulin secretion?
- High plasma glucose levels. Glucose enters beta cells through GLUT2 transporters
- Glucose is then phosphorylated to glucose-6-phosphate by glucokinase and this enters the Krebs cycle and oxidative phosphorylation leading to a rise in the ATP/AMP ratio
- High ATP inhibits K(ATP) channels and reduces K+ effluent
- So the membrane depolarises causing Ca2+ channels to open, intracellular Ca2+ levels increase
- Ca2+ triggers exocytosis of insulin-containing granules
- Membrane is repolarised
What does insulin do?
- increase glucose uptake into target cells and glycogen synthesis via insertion of GLUT4 channels
- inhibits breakdown of fatty acids
What are the effects of insulin in the liver?
- increases glycogen synthesis by stimulating glycogen formation and inhibit breakdown
- inhibits breakdown of amino acids
What are the effects of insulin in the muscles?
Increases uptake of amino acids which promotes protein synthesis
What are the effects of insulin in adipose tissue?
Increases the storage of TAGs
