Plasma Osmolality Flashcards
what detects a change in plasma osmolality
osmoreceptors
where are osmoreceptors found
in the OVLT of the hypothalamus
what responses are activated due to an increase in plasma osmolality
thirst response and ADH response
when is the thirst response stimulated
when the plasma osmolality has increased by 10%
what types of aqua porins are always found in the DCT and CD
types 3 and 4
what does ADH do
increase the expression of aqua porin 2 channels in the DCT and CD
on which membrane of the cells are aqua porin 2 channels found
apical membrane
on which membrane side of the cells are aqua porins 3 and 4 channels founds
basolateral
true or false: ADH causes diuresis
false - as water will be reabsorbed and not lost into the urine
what is central diabetes insipidus
where theres too little ADH
what causes central diabetes insipidus
hypothalamus injury, tumour, aneurysm
how is central diabetes insipidus treated
oral ADH spray
what osmolality changes in the plasma and urine will occur in central diabetes insipidus
high plasma osmolality
low urine osmolality
what is nephrogenic diabetes insipidus
where problems with the kidneys mean they don’t respond to ADH
what will the urine be like in diabetes insipidus
large volumes of dilute urine
true or false: the thirst response will be activated in diabetes insipidus
true
why do patients get polyuria in diabetes mellitus
as theres glucose not being reabsorbed and so left in the nephron tubules - this means more water stays in the tubules as the concentration gradient has decreased, so more water is lost in the urine
why do patients get polydipsia in diabetes mellitus
as they are losing more water in the urine, their plasma osmolality increases activating the thirst response, making them drink more
what does SIADH stand for
syndrome of inappropriate ADH
what is SIADH
where too much ADH is released
what happens to the plasma and urine osmolalities in SIADH
plasma - decrease
urine -increase
describe the movement of urea in the nephron
goes through the ascending loop of henle, through the DCT and CD - then diffuses into the interstitum
why is urea recycled in the nephron
to increase the concentration deep in the medulla
through what channels does urea go through in the kidney when its being recycled
aqua porin channels
true or false: urea recycling is ADH dependant
true - as the urea must travel through aqua porins
what sets up the concentration gradient from the cortex to the medulla
the ascending limb of the loop of henle
how does the loop of henle set up the concentration gradient in the cortex to medulla
the ascending limb transports salts out into the interstitum
the salts causes water to move into the interstitum from the descending limb of the loop of henle
the movement of salts and water helps to create the gradient
what are the vasa recta
the blood vessels running parallel to the loop of henle of jutxamedullary nephrons
what preserves the concentration gradient in the interstitum
vasa recta
how does the vasa recta conserve the concentration gradient
by taking up the water lost from the descending limb so that it doesn’t dilute the interstitum
what is the concentration at the bottom of the medulla in the interstitum
1200 mOsm
what is the concentration in the cortex/top of the interstitum
300 mOsm
true or false: at the top of the interstitum, the osmolality is isotonic with plasma
true
true or false: at the top of the ascending limb of the loop of henle, the osmolality is isotonic with plasma
false - it is actually hypotonic (100 mOsm)
