14 Flashcards
How does the kidney make urine that is more concentrated than plasma?
kidney can concentrate the urine up to 4 times of the plasma osmolarity of ~300 mosmol/l.
Concentrated urine can only be formed if there is concentrated fluid in the extracellular space in the renal medulla
In the normal kidney, the osmolarity of the extracellular fluid in the renal medulla is much higher than that of plasma
whats the vasa recta
capillary network surrounding the loops of Henle of juxtamedullary neurones
where are NA pumps
distal convoluted tubule
which tubule is the thin? thick?
thin is descending
thick is ascending
thick bc impermeable to water
what side of the epithelial cells is sodium pumped out of
basal
name of Chanel that takes 2cl k and na from urine to capillaries
NKCC2
what mechanisms regulate blood volume?
- neuronal sensors in the right atrium which have stretch receptors
Send afferents nerve fibres to medullary cardiovascular centres. - hormones. triggered by nerve impulse. stretch cells in RA release ANP. which increases water loss so lower blood volume.
Muscle cells in ventricles can release BNP. same mechanism.
- osmoreceptors in hypothalamus (supraoptic and paraventricular nuclei) take to posterior pituitary capillaries. secrete ADH.
which hormone decreases water loss
renin and aldosterone
which receptors sense osmolarity changes and release ADH as a result
osmoreceptors in hypothalamus (supraoptic and para ventricular receptors)
what senses blood sodium levels
sodium detectors in kidneys
what senses blood volume
hormonal and neuronal receptors in atria
If blood volume is too high but osmolarity and sodium levels are normal, what mechanism fixes the problems
the hormonal and neuronal receptors in the right atrium which release ANP and BNP to increase water loss
If blood volume is too high and osmolarity & sodium levels are low, what mechanism fixes the problems
- osmoreceptors in the hypothalamus which sends axons down to posterior part of pituitary capillaries to release ADH
After haemorrhage blood volume will be low; osmolarity and sodium will also be low due to water moving into blood from tissues. what mechanism fixes the problems
you want tp increase blood volume and osmolarity
so
hypothalamus surpaoptic and paraventral axons send to the posterior pituitary in capalaries to release ADH.
you can also reduce ANP and BNP recreation from the right atrium.
increase renin and aldosterone action.
what behaviour do osmoreceptors so supraoptic and paraventral nuclei of hypothalamus also trigger
thirst
which has a greater osmolarity, ECF in medulla or plasma
ECF in medulla
osmolarity of medulla )you know this=
1200 mmosml/L
where are aquaporins found
in descending limb of LoH.
what happens in ascending part of LoH
MEMBRANE PUMPS MOVE SODIUM AND CHLORIDE IONS FROM PLASMA TO EXTRACELLULAR SPACE BY ACTIVE TRANSPORT.
what vasculature supplies the loop of hence
vasa recta
whats the osmolarity of the fluid entering the DCT
100 mols/L
in the ascending loop of H what mechanism transports na out
theres a ROMK receptor that transports K out fo the cell into capillaries. this makes capillary side more positive w a voltage difference of 80 mV.
so Na
K
2Cl move other way, toward blood.
in the ascending loop of H where does Na go to and from
from the urine (basal side) to the ISF (blood)
how do Cl and Na and K make it to ISF
NAKCC from urine to cells
NAK pump
CL and K via passive diffusion
what is the mode of action of loop diuretics
act on loop of henle
block the action of NAKCC (furosemide)
what kind of drug is furosemide and on what Chanel does it act on
loop diuretic
ascending loop of h
what can high doses of furosemide cause
hearing loss bc NAKCC transporter exists in ear too
where does fine tuning of active transport of material takes place
distal CT
what is the site of ADH action
CD
what is the role of urea and where does it act
on CD
it gets pumped into the ISF to concentrate the medulla
concentrated medulla makes more concentrated urine.
does all urea get reabsorbed in ISF and medulla
no some of it gets reabsorbed in ascending loh to contribute to urea cycle
and some is lost in urine.
where does most urea go
medulla via ISF
what type of transport transports urea from CD to AL of LOH
active
explain the countercurrent multiplier mechanism of urine concentration
pumping out salt into ECF around LOH to concentrate urine (urea cycle)
what provides countercurrent exchange
vasa recta to preserve concentration gradient despite a blood flow through the vasa recta.
how is the pumping of salts in ECF compensated
via countercurrentexchange action of vasa recta.
what are the different types of diuretics that exist
1) thiazide diuretics,
2) ‘loop’ diuretics such as furosemide,
3) aldosterone antagonists spironolactone
whats the effect of ethanol on ADH action
inhibits ADH release so more urine. like water!
how do animals live in very cold weathers
countercurrent exchange
whats water diuresis
you drink too much water
ADH release is inhibited
highly diluted urine
you get DIABETER INSIPIDUS
whats osmotic diuresis
if too much glucose in blood. doesn't get absorbed like it should so it stays in urine that drives salts to urine. drives water to urine so you get DIABETES MELLITUS
what causes diabetes insipidus
water diuresis
what causes DIABETES MELLITUS
osmotic dirusis
think of Miel
