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
How does insulin decrease glucose concentration?
Causes insertion fo GLUT4 into membranes
Is glucagon water or lipid soluble? Which protein does it bind to?
Water soluble
Specific G protein receptor
WHen is glucagon released?
After meal due to AA increased
What is somatostatin? Is it paracrine or autocrine?
Growth inhibiting hormone
Inhibits insulin and glucagon
What is type 1 and type 2 diabetes melltius?
Inadequate secretion of insulin
Inadequate response to insulin
Why does hyperglycaemia cause weight loss?
Decreased protein synthesis
Muscles are broken down
What causes polydypsia? How?
Glucosuria
Causes water to be draw into nephron
Dehydration stimulates osmoreceptors in hypothalamus
Where is calcium found in the body? Give %
99% bone
1% ECF/ICF
Is calcium mainly intracellular or extracellular? Why?
Extracellular - used in cell excitation
What activates vitamin D3? What does this vitamin do?
UV and kidneys
Increase calcium int he blood
What does calcitriol do? Which hormone stimulates its production? What solubility is it?
Increases calcium absorption in kidneys
Metabolises bone
Stimulated by parathyroid hormone
Lipid soluble.
Why is lots of calcium used in late pregnancy?
Mammary glands - milk production
Mineralisation of foetal skeleton
What affect does kidney failure have on calcium and phosphorus?
Retained phosphorus
Decreased vitamin D - decreased calcium
What does calcitonin do? Where is it produced? Is it essential?
Decreases calcium - targets osteoclasts/GI secretion
Thyroid (parafollicular cells)
Not in vertebrates
How many glands are there in the parathyroid? Where are they found?
2
Lobes of thyroid
Which cells make parathyroid hormone?
Parathyroid Chief cells
How does parathyroid hormone cause calcium increase?
Causes release of calcitriol
Parathyroid hormone is produced by some cancers. What does this lead to?
Hypocalcaemia
Most phosphorus is found in the bone. What is it bound as?
Hydroxyapatite
How is inorganic and organic phosphorus found?
Inorganic - ions
Organic - ATP, phospholipids, nucleotides
WHat is milk fever? What are the symptoms and whY?
Parturition hypocalcaemia
Recumbency, rumen stasis, bloat, pupil dilation, neck kink
Due to poor smooth muscle contractio
Why are older cows more prone to milk fever than younger ones?
Younger cows - bone remodelling provides calcium
Older cows - skeleton non mobile
What is hypocalcaemia tetany? Which species is it found in?
Lack of calcium causing repeated firing of skeletal muscle - shaking
Lactating pigs/bitches
