session 10-pituitary and adrenal gland functions Flashcards
what 2 roles does phosphate have?
- role in energy metabolism
- activates/inactivates enzymes
what are hydroxyapatite crystals made from and where are they found?
- calcium and phosphate
- bone
what 3 hormones regulate calcium and phosphate levels?
- PTH (increases blood plasma levels of both)
- calcitriol (active form of vitamin D and also increases blood plasma levels)
- a bit of calcitonin (synthesised in parafollicular cells of thyroid gland and decreases blood plasma levels of Ca2+-preserve maternal skeleton during pregnancy)
what are the 5 main roles of calcium (Ca2+)?
- hormone secretion
- nerve conduction
- activate/inactivate enzymes
- muscle contraction
- exocytosis
what 3 places do the hormones PTH, calcitriol and calcitonin act on?
- kidneys
- GI tract
- bone
what happens to PTH when Ca2+ levels increase?
increases PLC (phospholipase c)—>decrease adenylate cyclase—>decrease cAMP—>decrease PTH
How does PTH affect the kidney tubule cells in terms of calcium reabsorption?
-increases calcium reabsorption in DST
how is calcium stone formation prevented in the kidney?
Pi is removed from circulation by inhibition of kidney tubule
why does hypocalcaemia cause tetany?
-low amounts bound to NMJ membrane, meaning Na+ channels stay open on motor end plate, constantly depolarising it and causing muscular contractions
what are the consequences of hypercalcaemia?
- kidney stones (too much Ca2+, therefore is excreted in urine, but forms crystals with other substances in urine)
- dehydration
- constipation
- kidney damage
- tiredness and depression
what does PTHrP do, what doesn’t it do and and where is it produced?
- produced in tumours e.g. myeloma and lung cancer
- acts like PTH=increases Ca2+ release from bone, increases Ca2+ reabsorption in kidney, decreases reabsorption of phosphate
- DOES NOT increase calcitriol concentration
- high levels of PTHrP (PTH related peptide) can uncover unexplained hypercalcaemia
Name the 3 zones in the adrenal cortex and state what each zone is responsible for.
zona glomerulosa=mineraloccorticoids
zona fasciculata=glucocorticoids
zona reticularis=androgens
the binding of ACTH to a corticotrophin receptor in the fasciculata and reticularis leads to…
activation of CHOLESTEROL ESTERASE and increases free cholesterol levels from which cortisol can then be synthesised.
Give 5 functions of cortisol
- regulate blood glucose levels
- fat,protein and carbs metabolism to maintain blood glucose
- immune response
- blood pressure
- affects cardiac muscle and bone
Aldosterone stimulates Na+ reabsorption in the kidneys which causes what and how?
- hypertension (high Na+ in blood decreases WP and so water moves out of kidney into blood=increase pressure on vessel walls)
- muscle weakness (tetany)
