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)
over secretion of androgens in females causes what? Give 3 things
- hirsuitism=hair growth
- deep voice
- increase muscle bulk
Oestrogen hormones are found in large amounts in which gender?
female
what is the difference between the action of adrenaline and cortisol on target cells?
adrenaline doesn’t cross CSM-binds outside to cause secondary messengers inside to activate e.g. adenyl cyclase
cortisol binds inside cell then enters nucleus to interact with specific regions of DNA
give the pathway of adrenaline synthesis starting from tyrosine
tyrosine->dopa->dopamine->noradrenaline->adrenaline
Give 3 clinical consequences of an over secretion of adrenaline and what is the medical name for this?
- sweating
- hypertension
- pallor
- anxiety
-phaemochromocytoma
