The Endocrine Pacreas Flashcards
Role of digestive enzymes in pancreas
Proteases (trypsin & chymotrypsin)- trypsin cleaves trypsinogen & chymotrysinogen. Pancreatic lipase- digests triglycerides. Pancreatic amylase- digests starch to glucose.
What are the major cell types in islets?
Beta cells- insulin, Alpha cells- glucagon, Delta cells- somatostatin
Insulin vs glucagon.
Insulin dominates the fed state and acts to lower plasma glucose. Glucagon dominates in the fasted state and acts to raise plasma glucose.
Describe the structure of insulin.
51 amino acid peptide hormone that is made of 2 chains- the A and B chains are held together by 2 disulfide bonds.
Beta cell at rest vs insulin secretion
At rest- the Katp channel is open and the cell is at its resting membrane potential. Secretion- Katp channels close, less K+ leaves cell causing the cell to depolarise. Ca2+ channel opens and Ca2+ entry triggers exocytosis and insulin in secreted.
How does insulin exert its effect on cells?
Insulin binds to the insulin receptor, receptor auto-phosphorylation, recruitment and activation of signalling complexes at cell membrane. This has effects on metabolic pathways and glucose uptake.
What are the main target tissues insulin acts on?
Liver, skeletal muscle and adipose tissue
Describe the structure of glucagon.
A 29 amino acid peptide hormone with no disulfide bonds. It is a major catabolic hormone of the body that opposes the actions of insulin.
Hat does glucagon promote in the liver?
Glycogenolysis-breakdown of glycogen to glucose, gluconeogenesis- synthesis of glucose
Control of glucagon release.
Katp channels close in response to a fall in glucose concentration, depolarisation of cell membrane opens voltage-gated Ca2+ channels allowing influx of Ca2+ triggering exocytosis of glucagon from vesicles.
How does glucagon exert its effect on cells?
Binds to the glucagon receptor, G-protein activation, effector protein activation, 2nd messenger deformation. This has effects on metabolic pathways and gene expression.
