Pancreas Flashcards
What happens in the islets of Langerhan’s?
This is where the endocrine function of the pancreas takes place, and where hormones are secreted from.
List the five hormones secreted by the pancreas.
Insulin, glucagon, somatostatin, pancreatic peptide, ghrelin.
What is the action of high blood glucose on the pancreas?
This stimulates the release of insulin, which causes fat cells to take up glucose.
What is the action of low blood glucose on the pancreas?
This causes the liver to release glucagon and this promotes the breakdown of glycogen in the liver.
Why does polyuria occur in diabetes?
When blood glucose is raised, it can go above the renal threshold leading it to be excreted by the kidneys. This affects the ability of the kidneys to reabsorb water and so leads to polyuria which then leads to Polydipsia.
What is C peptide?
This is the part of the peptide which is cleaved during the production of the insulin molecules. For patients who are receiving synthetic insulin the level of this indicates their B cell function.
What is the zymogen for insulin?
Preproinsulin. This folds in the Golgi forming 2 disulphide bond before the peptide chain in the middle (C peptide) is cleaved.
How is insulin secreted?
When insulin is synthesised it is packaged into granules. These granules move to the cell surface before exocytosis occurs and contents are released.
In insulin secretion, what is margination?
This is movement of the insulin containing vesicles to the cell surface.
How is insulin secretion controlled?
High glucose acts as a stimulus and is transported into cells and leads to depolarisation of the membrane. This leads to an increase in Extracellular calcium. Intracellular calcium increases and stimulates exocytosis.
What happens when insulin binds to a cell receptor?
There are 2 identical subunits which span the membrane. The A units on the outside of the cell move together and so do the B subunits on the inside. This leads to activation of tyrosine kinase which phosphorylates. This cascade leads to opening of GLUT4
When is glucagon released?
Glucagon is secreted when glucose is low. It mobilises energy release.
State the two functions of the pancreas
Endocrine and exocrine.
