ion and water balance part 3 Flashcards
what is urea
metabolic waste byproduct
produced in the liver and transported in the blood
impermeable to the nephron–> secreted
why does the body control movement of potassium
too much potassium in the body will depolarize cell membranes
- catastrophic in heart and brain
how does vasopressin increase water reabsorption
- vasopressin binds G protein linked receptor
- receptor activates adenylate cyclase–> cAMP–> pKA
- pKA phosphorylates cytoskeletal and vesicle proteins
- translocation of aqaporin to the membrane
vasopressinn characteristics
- also called antidiuretic hormone (ADH)
- produced in hypothalamus–> released by posterior pituitary
- increase water reabsorption from collecting ducts and distal tubules
how is vasopressin stimulated/inhibited
stimulated- increasing plasma osmolarity detected by osmoreceptors in the hypothalamus
inhibited- increasing blood pressure detected by stretch receptors in atria and baroreceptors
how does aldosterone stimulate Na reabsorption
- aldosterone diffuses into cell
- binds to transcription factor
- activated transcription factor stimulates transcription of genes for transporters
- new transporters made in ER and exported
- vesicles containing proteins sent to plasma membrane
(Na/K ATP ase)
aldosterone characteristics
mineralocorticoid controls ion excretion
produced by adrenal cortex
steroid hormone
stimulates Na reabsorption and K secretion
produces Na/K ATP ase and K and Na channels
what inhibits/stimulates aldosterone
stimulated- angiotensin 2, high K, ACTH, decreased blood pressure
what is the Renin-Angiotensin-Aldosterone pathway (RAA)
juxtaglomerular cells secrete renin (enzyme) controlled by: baroreceptors sympathetic neurons of medulla oblongota macula densa cells in distal tubule
when is renin secreted
in response to low blood pressure
in response to low glomerular filtration rate
what does renin do
converts angiotensinogen to angiotensin 1
ACE converts angiotensin 1 to angiotensin 2
what does angiotensin 2 do
causes synthesis and release of aldosterone from adrenal cortex
release of vasopressin
potent vasoconstrictor
