Physiology: pancreas Flashcards
ANATOMY
The pancreas has two types of tissues
- What is the exocrine tissue?
- What is the endocrine tissue?
Exocrine tissue: acinar cells (and duct cells)
Endocrine tissue: Islets of Langerhans
ANATOMY
What are the 4 cell types in the Islets of Langerhans?
–> How to remember?
Beta cells (60%): secrete insulin and amylin
Alpha cells (25%): secrete glucagon
Delta cells (10%): secrete somatostatin
PP cells (smaller numbers): secrete pancreatic polypeptide, which has an unknown role
–> In diabetes, you get a bad PP
ANATOMY
The Islets of Langerhans are well vascularised.
Describe their venous drainage; implications for hormone concentrations
Hormones enter the pancreatic vein and then travel to the hepatic portal vein
Pancreatic enzymes have higher concentrations in the liver versus peripheral tissues
INSULIN
- Two stimuli for insulin secretion
Increased BGLs
Amino acids
INSULIN
Role of beta cells in regulating insulin secretion?
ATP binds to K+ channels, closing them –> depolarisation
This depolarisation leads to opening of voltage gated Ca2+ channels –> Ca2+ influx –> exocytosis of insulin granules
INSULIN
Describe how insulin binds to receptors on target cells
Insulin binds to the alpha subunit of insulin receptor
This triggers the autophosphorylation of the beta subunit, which induces tyrosine kinase activity
Phosphorylation events mediate the cellular impacts of insulin
INSULIN
Effects
- What impact does it have on BGLs?
- What 3 tissues does it act on?
Increased glucose uptake and utilisation; and storage.
Acts to decreased BGLs overall –> restoring them to normal levels
Liver, skeletal muscle, adipose tissue
INSULIN
Effects
- Fill in this table
GLUCAGON
- What are its two stimuli?
Decreased BGLs
Amino acids (eg. protein rich meal)
GLUCAGON
Describe its effects
Stimulates glycogenolysis and GNG in the liver —> increased BGLs (restored to normal levels)
Amino acids stimulate the release of both insulin and glucagon.
Impact on BGL?
Minimal impact on BGLs - as it doesn’t change the insulin : glucagon ration much
DIABETES MELLITUS
Glucose tolerance testing in heatlhy person vs person with type I diabetes?
DIABETES
What are the three cardinal symptoms of diabetes?
Polyuria - impaired glucose reabsorption –> glucose builds up in kidney tubules –> creates osmotic pressure which drives water into the tubules
Polydipsia - from water loss due to polyuria
Polyphagia - cells cannot take up glucose and are “starving”
DIABETES
What are the microvascular and macrovascular complications of diabetes?
Microvascular complications: neuropathy, retinopathy, nephropathy
Macrovascular complications: CVD
DIABETES
What occurs when insulin isn’t produced