Endocrine System 1&2 Flashcards
What are examples of local signalling?
Paracrine - bind to neighbour cell
Autocrine - bind to self
In the pancreas. there are 2 lobes. What is the structure of the exocrine pancreas?
Cells arranged into acini and ducts, produce digestive enzymes
Across acini are islets of Langerhans
What are the 4 types of islets of Langerhans? WHat do they produce?
A - glucagon
B - insulin
Delta - somatostatin
F - pancreatic polypeptides
What is the prohormone for insulin? What needs to happen to it before it is active?
Proinsulin
Inactive c protein removed
Is insulin water soluble or fat soluble? Which receptor does it bind to?
Water soluble
Tyrosine kinase
How do B cells directly detect an increase in blood glucose?
Glucose enters cell via GLUT2 Fuels ATP formation ATP sensitive K+ channels are blocked K+ accumulation leads to depolarisation Opens voltage gated calcium channels Calcium causes exocytosis of insulin
Insulin is controlled by which GI hormones?
GIP & GLP - released before absorption
Cellular uptake of glucose is independent of insulin in which parts of the body?
Brain
Mammary tissue
GI
Kidney tubules
How does insulin enter a cell?
Second messenger model
Alters proteins, modifies membrane transport
Glucose leaves cell by which transporter? (Insulin increase number of these)
GLUT4
When fasted, hepatocytes make glucose-and transport it. When fed they also enter cells using which transporter?
GLUT2
Insulin stimulates the conversion of glucose to glucose-6-phosphate inside cells. Which enzyme does this? Why is this important?
Hexokinase
Maintains conc gradient - allows more glucose to enter cell
What is different about cells in the CNS?
They are not sensitive to insulin
But rely on glucose metabolism - they can’t metabolise fats etc
Why can hyperglycaemia be fatal?
XS glucose in CSF
Draws water out of cells
Causes dehyrdation
What is glucagon?
Hormone stored in active form
