kidney

Question 1

normal Osmolarity of urine is ___?

Answer 1

200 mOsm

Question 2

how does kidney try to help us in times of dehydration?

Answer 2

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

Question 3

% cardiac output kidneys receive?

Answer 3

20%!!

Question 4

how many loops of henle do we have?

Answer 4

a million- each nephron has their own microcirculation!

Question 5

where does filtration occur?

Answer 5

glomerulus

Question 6

GFR

Answer 6

GFR = glomerular filtration rate = 120 mL/min (all nephrons working all together)

Question 7

where does reabsorption occur?

Answer 7

proximal tubule

Question 8

reabsorption takes back what % of filtrate?

Answer 8

Takes back 75-90% of filtrate

Question 9

ADH function?

Answer 9

ADH decreases urine flow, promotes water reabsorption

Question 10

how does ADH feedback loop work?

Answer 10

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

Question 11

If osmolarity gets concentrated (goes up) body does what?

Answer 11

release more ADH or vasopressin to reabsorb more water

Question 12

graph of plasma osmolarity (x axis) vs ADH?

Answer 12

straight line, increasing (more osmolarity concentration -> more ADH secretion)

Question 13

in the ascending limb, what are the 2 mechanisms by which we move salt out?

Answer 13

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

Question 14

what is the vasa recta?

Answer 14

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.

Question 15

what is lasix and what does it do?

Answer 15

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.

Question 16

what is autoregulation of kidney based on?

draw graph of renal blood flow/GFR

Answer 16

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.

Question 17

describe what happens to GFR if you constrict/dilate afferent arteriole or constrict efferent arteriole

Answer 17

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

Question 18

what intrinsic property of smooth muscle in afferent arteriole contributes to autoregulation of nephron?

Answer 18

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.

Question 19

what do macula densa cells do ?

Answer 19

special set of cells assoc. w/ distal tubule

secrete renin, an enzyme. (macula dense + JG cells secrete it)

Question 20

what does renin do?

Answer 20

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

Question 21

what does aldosterone do?

Answer 21

Increases sodium retention

Increases potassium excretion

acts on distal tubule.

Question 22

what does the afferent arteriole do?

Answer 22

afferent arteriole acts as barometer; if it sees too much pressure, it will constrict

Question 23

what does the hormone ANF do? what 3 areas does it act on?

Answer 23

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

Question 24

why was PAH useful in WW2?

Answer 24

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.

Question 25

what does the drug Lasix do?

Answer 25

inhibits sodium reabsorption

Question 26

describe all effects that occur when blood pressure drops

Answer 26

1. increase osmolarity, urine concentration, ADH, GFR!!!
2. decrease urine output
3. constrict EFFERENT arteriole to increase back pressure

(osmoreceptors sense dehydration, increase adh)