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Urinary > Week 4 - Plasma Volume > Flashcards

Week 4 - Plasma Volume Flashcards

1
Q

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

A

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

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2
Q

Why must water and salt be added/removed together?

A

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

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3
Q

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

A
  • If they are reduced it promotes Na and water reabsorption

- If they are increased it inhibits Na and water reabsorption

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4
Q

What are the target cells of aldosterone?

A

-Principle cells of late DCT and CD

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5
Q

What is the connection between Na and Cl reabsorption?

A
  • NaKATPase on basolat geeratea Na gradient

- Na resorption occurs down its gradient with Cl accompanying it to maintain electro-neutrality

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6
Q

Name the transporters found in the PCT?

A
  • NHE
  • Na:Glucose
  • Na:a’a
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7
Q

Name the transporter of LoH?

A

-NKCC2

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8
Q

Name the transporter of DCT

A

-NCC2

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9
Q

Name the transport channel of late DCT and CD

A

-ENaC

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10
Q

Why is it significant that the tubular cells are polarised?

A

-Stop transporters from switching membranes

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11
Q

What governs uptake of solutes into peritubular capillaries?

A

-Concentration gradient

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12
Q

What is the difference between S1 of PCT and S2?

A

-Different apical Na transporters

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13
Q

What transporters are involved in S1 of pct?

A
  • NaKATPase and NaHCO3 on basolat

- NHE, Na:glu, Na:a’a and NaPi on apical

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14
Q

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

A
  • Increases to compensate for loss of glucose

- Creates a conc gradient for chloride reabsorption in S2-3

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15
Q

What transporters are involved in S2 of pct?

A
  • NaKATPase on basolat

- NHE, paracellular Cl-, Transcellular Cl-

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16
Q

What drives water reabsorption into peritubular capillaries?

A
  • Osmotic gradient caused by solute reabsorption
  • Hydrostatic force of interstitium
  • Oncotic pressure in peritubular capillary
17
Q

What is glomerulotubular balance?

A
  • 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
Q

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

A

-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
Q

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

A

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

20
Q

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

A

-Ascending

21
Q

Describe Na reabsorption in the ascending limb of loop of henle

A
  • 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
Q

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

A
  • 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
Q

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

A
  • Thick ascending limb

- Uses alot of energy to function NKCC2 and NaKATPase

24
Q

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

A

-Solute and water reabsorption is separated in the loop

25
Q

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

A

-Hypo-osmotic

26
Q

What is the function of the DCT?

A

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

27
Q

What determines that water permeability of late DCT and CD?

A

-ADH

28
Q

What diuretics target NCCT?

A

-Thiazide

29
Q

How much Na is reabsorbed in DCT?

A

-5-8%

30
Q

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

A
  • Calcium

- PTH

31
Q

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

A
  • Principle cells

- Intercalated cells

32
Q

What are the function of principle cells and intercalated cells?

A
  • Principle cells -> Reabsorption of Na via ENaC

- Intercalated cells-> Active Reabsorption of Cl, Secretion of H or HCO3

33
Q

Describe Na Reabsorption by Principle cells

What effect does this have on Cl reabsorption

A
  • 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
Q

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

A
  • 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
Q

What is pressure natiuresis and diuresis?

A
  • 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
Q

What is the major osmotically effective molecule in ECF?

A

-Na

Urinary (21 decks)

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