the pancreas Flashcards
What is proinsulin?
precursor of insulin synthesised in pancreas that’s cleaved into insulin
How is insulin derived from proinsulin?
c-peptides are cleaved to leave an A and B chain joined by disulphide bridges
How do insulin and proinsulin relate in terms of biological activity?
proinsulin is inactive
insulin is active
Where does the conversion of proinsulin to insulin occur?
in the Golgi of pancreatic B cells
What is the primary stimulus for insulin secretion?
increased blood glucose
what is the islet of langerhan
bundle of endocrine cells in the pancreas
pancreatic alpha cells secrete ?
glucagon
pancreatic delta cells secrete
somatostatin
pancreatic F cells secrete
pancreatic polypeptide
functional cells are present at ___ months at gestation in utero
6
The final cleavage of insulin produces ___________ amounts of C peptide
equimolar
Fasting blood glucose =
4-5mmol l-1
postpandrial blood glucose=
up to 10mmol l-1
name stimulants insulin release
blood glucose concentration
incretins (GLP-1, GIP)
glucagon
hyperkalaemia
vagal nerve stimulation
name inhibitor of insulin release
somatostatin
epi and norepi
what is more substantial ingested glucose or injected?
ingested
How do fatty acids influence insulin secretion?
elevated free fatty acids stimulate insulin secretion but can cause insulin resistance
Where does insulin synthesis begin in the cell?
in ribosomes of rough ER of pancreatic B cells
What is the initial form of insulin called?
preproinsulin
How does glucose entry into β-cells lead to insulin secretion?
glucose enters pancreatic B cells via GLUT2 leading to increase in intracellular ATP this closes ATP sensitive K channels
What happens when ATP-sensitive K⁺ channels close in β-cells?
cell becomes depolarised and Ca channels open
How does calcium affect insulin release?
Ca influx causes insulin vesicles to fuse with cell membrane and therefore insulin secretion
glucose is converted to ______ by glucose kinase
glucose-6-phosphate
why is glucose-6-phosphate inportant in insulin secretion
it undergoes TCA cycle to increase intracellular ATP needed to drive Ca influx
What is the precursor molecule to glucagon?
preproglucagon
How is preproglucagon processed to form glucagon?
cleaved in rough ER to form proglucagon then further processed to active glucagon
What is the primary stimulus for glucagon secretion?
hypoglycaemia
Name an amino acid that stimulates glucagon secretion.
alanine and arginine
How does exercise affect glucagon secretion?
stimulates glucagon secretion
name stimulates of glucagon secretion
GIP
epi
hypoglycaemia
name inhibitors of glucagon
GLP-1
hyperglycaemia
somatostatin
insulin and amylin
What is the primary role of insulin in glucose homeostasis?
lowers blood glucose by promoting glucose uptake in cells and storing glucose as glycogen
How does glucagon affect blood glucose levels?
raises blood glucose levels by stimulating processes like glycolysis and gluconeogenesis in liver
When is insulin secreted to regulate glucose?
after meals when blood glucose is high
When is glucagon secreted to regulate glucose?
during fasting or when blood glucose levels are high
What is the effect of insulin on glycogen synthesis?
promotes glycogen synthesis in muscles and liver to store excess glucose
How do insulin and glucagon work together to maintain glucose balance?
insulin decreases blood glucose when levels are high and glucagon increases blood glucose when levels are low
What happens to insulin and glucagon secretion during hypoglycemia?
insulin secretion decreases
glucagon secretion increases
What happens to insulin and glucagon secretion during hyperglycemia?
insulin secretion increases
glucagon secretion decreases
What is Type 1 Diabetes Mellitus?
autoimmune disease where body attacks pancreatic B cells leading to insulin deficiency
What causes Type 2 Diabetes Mellitus?
insulin resistance due to pancreatic B cell dysfunction
What are insulinomas?
rare pancreatic tumours that produce excessive insulin
What is pancreatitis and how does it affect endocrine function?
inflammation of pancreas
What is gestational diabetes?
diabetes that occurs usually in the 2nd or 3rd trimester of pregnancy
What is a closed-loop system in Type 1 Diabetes management?
insulin pumps and continuous blood glucose monitors
How does a closed-loop system differ from traditional insulin therapy?
manual insulin dosing
