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Flashcards in Week 4 - Plasma Volume Deck (36):
1

Why must Na excretion be able to change in the kidney?

-In order to maintain Na balance and match ingestion to excretion

2

Why must water and salt be added/removed together?

-If you removed one or the other you would change the osmolarity of plasma so addition/removal needs to be isotonic

3

What effect does osmotic and hydrostatic pressure of the peritubular capillaries have on Na reabsorption in PCT?

-If they are reduced it promotes Na and water reabsorption
-If they are increased it inhibits Na and water reabsorption

4

What are the target cells of aldosterone?

-Principle cells of late DCT and CD

5

What is the connection between Na and Cl reabsorption?

-NaKATPase on basolat geeratea Na gradient
-Na resorption occurs down its gradient with Cl accompanying it to maintain electro-neutrality

6

Name the transporters found in the PCT?

-NHE
-Na:Glucose
-Na:a'a

7

Name the transporter of LoH?

-NKCC2

8

Name the transporter of DCT

-NCC2

9

Name the transport channel of late DCT and CD

-ENaC

10

Why is it significant that the tubular cells are polarised?

-Stop transporters from switching membranes

11

What governs uptake of solutes into peritubular capillaries?

-Concentration gradient

12

What is the difference between S1 of PCT and S2?

-Different apical Na transporters

13

What transporters are involved in S1 of pct?

-NaKATPase and NaHCO3 on basolat
-NHE, Na:glu, Na:a'a and NaPi on apical

14

What happens to the concentration of Cl and Urea in S1? What affect does this have on S2?

-Increases to compensate for loss of glucose
-Creates a conc gradient for chloride reabsorption in S2-3

15

What transporters are involved in S2 of pct?

-NaKATPase on basolat
-NHE, paracellular Cl-, Transcellular Cl-

16

What drives water reabsorption into peritubular capillaries?

-Osmotic gradient caused by solute reabsorption
-Hydrostatic force of interstitium
-Oncotic pressure in peritubular capillary

17

What is glomerulotubular balance?

-A mechanism to control Na excretion in proportion to the volume of ultrafiltrate
-ie Blunts Na excretion response to any GFR change ->67% of Na in PCT always resorbed regardless of volume of ultrafiltrate

18

How is the medulla specialised for H2O reabsorption? What does this achieve?

-Has an increasing osmolarity into the medulla so water is drawn out of descending limb of loop of henle creating a hyperosmotic filtrate at the bottom of the loop

19

Why is it significant that the filtrate is hyperosmotic at the bottom of the loop of henle?

-Creates a concentration gradient for solutes so they can be pumped out of the ascending limb

20

Which limb in the loop of henle is impermeable to water?

-Ascending

21

Describe Na reabsorption in the ascending limb of loop of henle

-Na reabsorption is passive in the thin ascending limb through paracellular means
-Na reabsorption is active in the thick ascending limb by NaKATPase generating a gradient for NKCC2

22

How does K diffuse back into the interstitium from the thick ascending limb? Why is this vital?

-Leaky RomK channels allow K to diffuse out of tubule cells back into the filtrate
-Vital because NKCC2 uses K from the filtrate to function and pump Na into the tubule cell

23

Which part of the nephron is most sensitive to hypoxia and why?

-Thick ascending limb
-Uses alot of energy to function NKCC2 and NaKATPase

24

What is significant about solute and water reabsorption in the loop of henle?

-Solute and water reabsorption is separated in the loop

25

Describe the filtrate at the top of the ascending limb of loop of henle

-Hypo-osmotic

26

What is the function of the DCT?

-Fine-tune the filtrate to allow extra absorption of solutes and water

27

What determines that water permeability of late DCT and CD?

-ADH

28

What diuretics target NCCT?

-Thiazide

29

How much Na is reabsorbed in DCT?

-5-8%

30

Besides from Na, what other main solute is absorbed in DCT? What controls this?

-Calcium
-PTH

31

What are the two distinct cell types in the late DCT and CD?

-Principle cells
-Intercalated cells

32

What are the function of principle cells and intercalated cells?

-Principle cells -> Reabsorption of Na via ENaC
-Intercalated cells-> Active Reabsorption of Cl, Secretion of H or HCO3

33

Describe Na Reabsorption by Principle cells
What effect does this have on Cl reabsorption

-NaKATPase on basolat membrane creates Na gradient
-Concentration gradient for active uptake of ENaC
-No accompanying anion through ENaC so there is a negative charge created in lumen
-Driving force for paracellular Cl uptake

34

How does ADH influence water permeability in Late DCT and CD?

-ADH increases the expression of AQP2 channels on apical membrane of tubule cells
-AQP channels always present on basolat
-Water moves into interstitium down osmotic gradient

35

What is pressure natiuresis and diuresis?

-Increased renal artery bp
-Reduced number of NHE and NaKATPase in PCT
-Reduced Na and H2O reabsorption in PCT
-Thus increased Na (natriuesis) and H2O excretion
-ECF volume decreased
-BP decreases

36

What is the major osmotically effective molecule in ECF?

-Na