The Endocrine Pancreas Flashcards
How many islet cells are in the human pancreas?
1 million
Which islet cells secrete insulin?
Beta cells
Which islet cells secrete glucagon?
Alpha cells
Which islet cells secrete somatostatin?
Delta cells
Which islet cells secrete pancreatic polypeptide?
PP cells
Which islet cell secretes ghrelin?
Epsilon cell
What is the value for basal blood glucose level?
< 5.5mM
How many secretory granules are present on the beta cell?
10000
How many secretory granules are released per beta cell per day?
<1000
How much insulin is in each secretory granule?
8fg
What do the beta cells respond to in order to determine the correct amount of glucose for secretion?
Nutrients - amino acids, free fatty acids, glucose
Hormones - IL6, Leptin, Adiponectin, IGF1, Glucagon, GLP1, GIP
Neurotransmitters - Acetylcholine
What is the relationship between insulin sensitivity and insulin release in type 2 diabetes?
As insulin sensitivity decreases, insulin release does not increase to match.
What is meant by plasticity in beta cell function?
This is the ability of beta cells to adjust to the body’s demand for insulin
What is meant by biphasic insulin secretion?
In non-diabetics, there are two phases of insulin secretion - 1st phase when the insulin comes for RRP and the 2nd phase when it comes form stores.
In T2DM, the separation of these two phases is lost
How do alpha cells sense glucose?
- When glucose levels are low, the KATP channels will be partially open.
- The voltage gated sodium channels then partially open to contribute to the action potentials.
- There is then opening of calcium channels to cause calcium influx.
- This triggers glucagon exocytosis.
What is the role of glucagon in glucose homeostasis?
Glucagon is secreted from alpha cells in the pancreas and acts on the liver to stimulate hepatic glucose production. In turn the blood glucose acts on beta cells to secrete insulin which then reduces hepatic glucose secretion. Thus maintaining glucose homeostasis.
What happens to glucagon secretion in type 2 diabetes?
Glucagon secretion is dysregulated because of a lack of suppression at high glucose levels. Glucagon will still be secreted in the fed state.
What is somatostatin 14 secreted in response to?
Nutrient or hormonal stimulation
What is the action of somatostatin 14?
It suppresses beta cell and alpha cell function in a paracrine manner.
What does endocrine mean?
Glands that secrete hormones and other products directly into the blood
What does exocrine mean?
Glands which secrete their products into ducts through the epithelium
What does paracrine mean?
This relates to a hormone that has an affect on adjacent cells
What does autocrine mean?
A cell-produced substance that has an effect on the cell by which it is secreted
What does juxtacrine mean?
This is signalling that requires the close contact of cells.
What is the incretin effect?
Insulin secretion is greater from oral glucose relative to an isoglycaemic IV infusion
What type of pancreatic cells secrete GLP-1?
L-cells
What is the principle incretin hormone?
Glucagon Like Peptide 1 - it potentiates insulin secretion from pancreatic beta cells
What are the anorexigenic (satiety) signal?
Peptide YY
Oxyntomodulin
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