Pancreatic Endocrinology Flashcards
What proportion of pancreatic cells are acini?
98-99%
What do acini release?
EXOCRINE function.
Secrete digestive enzymes through pancreatic ducts and the ampulla of vata into the small intestine
What proportion of pancreatic cells are islets of Langerhans?
1-2%
What do the islets of Langerhans release?
ENDOCRINE function.
Secrete peptide hormones into the portal vein
Give the cell types of the islets of Langerhans and each hormone that they release.
Delta cells: Somatostatin
Alpha cells: Glucagon
Beta cells: Insulin
What are the effects of insulin?
- Increases glucose uptake into cells in response to high blood glucose levels
- Decreases glycogenolysis
- Increases glycogenesis
- Increases conversion of glucose to fatty acids
What is the target cell for insulin?
Hepatocytes and muscle cells
What are the effects of glucagon?
- Increases Glycogenolysis
- Increases Gluconeogenesis
- Stimulates lipolysis for respiration
What is the target cell for glucagon?
Hepatocytes
What is the precursor to insulin?
Proinsulin.
Which molecule is not present in synthetic insulin but is in natural insulin?
C peptide
Which glucose transporter is present in beta cells?
GLUT2
What is the affinity of GLUT2 to glucose?
Low affinity. Only binds when there is a high concentration of glucose.
Once inside the beta cell, which enzyme breaks down glucose into glucose-6-phosphate?
Hexokinase
Outline the steps of insulin release from beta cells.
- ATP binds to a K+ ATP channel and closes the channel
- K+ ions are unable to leave the cell, resulting in depolarisation of the beta cell membrane
- Voltage gated Ca2+ channels open and Ca2+ ions diffuse into the cell
- Ca2+ ions bind to insulin secretory granules
- Granules fuse with the cell membrane and release the insulin via exocytosis
Give the steps that follow when insulin binds to insulin receptors on cell membranes of muscles.
- Signalling cascade is triggered
- GLUT4 vesicles fuse with the cell membrane
- Results with a greater rate of glucose diffusion into the cell
- This decreases blood glucose levels
Where are glucose level sensors located in the body?
Islets of Langerhans
Medulla
Hypothalamus
Carotid bodies
Which peptides are secreted from endothelial cells in the GI tract in response to eating?
Incretins
In a fasting state, where is glucose produced?
Liver via glycogenolysis
How much ingested glucose goes to the liver?
40%. 60% goes to muscle.