kidney Flashcards
normal Osmolarity of urine is ___?
200 mOsm
how does kidney try to help us in times of dehydration?
Kidney can make a concentrated urine to help with dehydration (1200 mOsm) thus conserving water ADH is a hormone that helps the body to retain water by increasing water reabsorption by the kidneys
% cardiac output kidneys receive?
20%!!
how many loops of henle do we have?
a million- each nephron has their own microcirculation!
where does filtration occur?
glomerulus
GFR
GFR = glomerular filtration rate = 120 mL/min (all nephrons working all together)
where does reabsorption occur?
proximal tubule
reabsorption takes back what % of filtrate?
Takes back 75-90% of filtrate
ADH function?
ADH decreases urine flow, promotes water reabsorption
how does ADH feedback loop work?
In hypothalamus, there are special cells called osmoreceptors. Monitor osmolarity. If osmoreceptors see increase in osmolarity of plasma – means you are dehydrated- Response is to increase ADH secretion. send water out of collecting duct, into blood. this decreases urine volume (concentrates it) to preserve body water in short: ADH acts on collecting duct–will act on receptor that uses cAMP as second messenger -> will stimulate aquaporins to move water across cells
If osmolarity gets concentrated (goes up) body does what?
release more ADH or vasopressin to reabsorb more water
graph of plasma osmolarity (x axis) vs ADH?
straight line, increasing (more osmolarity concentration -> more ADH secretion)
in the ascending limb, what are the 2 mechanisms by which we move salt out?
1) diffusion, 2) ion pumps
We have concentrated salt so much that as filtrate comes up thru thin part, Na+ and Cl- reabsorbed down concentration gradient via passive diffusion
In thick part, have series of ion pumps –pump salt out of filtrate - Na+ and Cl- reabsorbed
what is the vasa recta?
vasa recta (extension of peritubular bed) is absorbing water from loop of henle. Any water we’re pulling out of collecting duct if ADH is around is going to get taken away by vasa recta. So flow thru vasa recta is very impt.
what is lasix and what does it do?
Lasix is loop diuretic; way you get rid of excess body fluid in fairly fast way is give loop diuretic, which inhibits ion pumps. If inhibit salt from leaving ascending loop of henle, salt stays in; remember that water goes to most concentrated areas, meaning water goes into the urine too, and you pee a LOT! sucks the fluid right out of you.
helps individual with (edema) to get rid of fluid.
what is autoregulation of kidney based on?
draw graph of renal blood flow/GFR
regulation of kidney is based on keeping GFR stable. So over wide range of arterial pressure, we keep renal plasma flow constant; by keeping renal plasma flow constant, we keep GFR constant.
describe what happens to GFR if you constrict/dilate afferent arteriole or constrict efferent arteriole
If take afferent arteriole and dilate it, more blood goes in -> GFR increases
If constrict afferent arteriole -> GFR decreases
Constrict efferent arteriole -> GFR increases (b/c get a bit of back pressure), at least temporarily
what intrinsic property of smooth muscle in afferent arteriole contributes to autoregulation of nephron?
if there’s an increased arterial pressure, smooth muscle responds by increasing smooth muscle contraction. If smooth muscle surrounding that vessel contracts, radius decreases -> flow into glomerulus decreases -> GFR decreases.
what do macula densa cells do ?
special set of cells assoc. w/ distal tubule
secrete renin, an enzyme. (macula dense + JG cells secrete it)
what does renin do?
secrete angiotensin 1- Renin’s primary function is therefore to eventually cause an increase in blood pressure, leading to restoration of perfusion pressure in the kidneys
what does aldosterone do?
Increases sodium retention
Increases potassium excretion
acts on distal tubule.
what does the afferent arteriole do?
afferent arteriole acts as barometer; if it sees too much pressure, it will constrict
what does the hormone ANF do? what 3 areas does it act on?
ANF, secreted from right atrium of heart, causes naturiesis - an increase in urine flow via increase in sodium excretion
senses if blood pressure is too high, and increases urine flow to try and decrease it
1) kidney: inhibits renin secretion, temp increase GFR, decrease Na reabsorption
2) Acts on adrenal gland: decrease aldosterone
Decrease Na+ reabsorption (increase H2O loss)
3) Acts on hypothalamus - decreases ADH secretion
So if don’t have antiduretic hormone, get diuresis! Increases urine flow
why was PAH useful in WW2?
At beginning of WWII, penicillin was first available; low supply in field. So gave penicillin and PAH- at same time; both were competing for organic ion transporter, so extended life of penicillin significantly.
