Pancreatic hormones Flashcards
3 pancreatic hormones
Insulin
Glucagon
Somatostatin
Insulin
Secreted by B-cells in the islets of langerhans
Main controller of blood glucose level
Increases uptake of glucose in cells via GLUT4, not in liver or pancreatic B-cells as they have GLUT2.
Increases synthesis of glycogen, decreases gluconeogenesis and ketogenesis. Overall effect to lower blood glucose.
Controlled by glucose.
Insulin and glucose transporters
Insulin binds to insulin receptor, causing signalling to glucose transporters which then translocate and dock to the cell membrane. Once they fuse with the cell membrane they are activated creating glucose uptake channels.
Control of insulin release
Glucose enters B-cells via GLUT2, this increases ATP to ADP ratio which in turn closes the ATP sensitive potassium channel (depolarisation). This opens voltage gated calcium channels which activates excytosis of insulin granules.
Effects of Glucagon
Mainly on liver
Stimulatees glycogen breakdown to glucose
Activates glycogen phosphorylase whilst inhibiting glycogen synthase.
Acts via glucagon receptor to activate adenylate cyclase, giving negative feedback by phosphorylation of above enzymes by PKA.
Diabetes mellitus type 1
Failure of secretion of insulin
Thought to be genetic or autoimmune destruction of B-cells.
Increased blood glucose, increased blood lipids, thirst and excessive urination, loss of weight and ketosis.
Treated with HRT insulin injection/pump.
Diabetes mellitus type 2
Due to failure of insulin action.
Diverse disease with multiple factor (insulin aantibodies, failure of receptor, failure of signal transduction).
Little point giving insulin unless it develops into type 1.
Oral hypoglycemics are used instead
Sulphonylureas - stimulate insulin release from B-cells, blocks ATP-K channel.
Biguanides - inhibit hepatic gluconeogenesis and increases tissue sensitivity to insulin
Thiazolidinediones - enhances insulin action in liver, muscle and adipose tissue.
