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MSS Renal Exam 2 > Mechanisms to Adjust Urine Concentration > Flashcards

Mechanisms to Adjust Urine Concentration Flashcards

1
Q

proximal tubule Na?

A

50-55% of reabsorption

  • cotransport with glucose, amino acids, phosphate
  • countertransport with H+

+2 mV

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2
Q

thick ascending limb Na?

A

Na/H/2Cl contransport

+10mV

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3
Q

early distal tubule Na?

A

5-8%
Cl cotransport

-70 mV
because Cl left over at greater rate because it can’t passive flow with the Na

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4
Q

late distal tubule Na and collecting duct Na?

A

2-3%
luminal Na channels

-70mV

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5
Q

water reabsorption

A

always passive
paracellular or transcellular

follows sodium

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6
Q

chloride reabsorption

A

always linked to Na reabsorption
-further down tubule, chloride can’t get across membrane

so thats why we have a negative luminal potential

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7
Q

descending limb of loop

A

permeable to water

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8
Q

ascending limb of loop

A

always impermeable to water

thin - NaCl reabsorption mechanisms unknown

thick - active Na/K/2Cl cotransport

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9
Q

thick ascending limb potential?

A

around +6
because of K+ leak channels

pushes Na, K, Ca, Mg, NH2 transcellularly

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10
Q

distal convoluted tubule first half?

A

Na/K ATPase
K leak channels

Na/Cl cotransporter (reabsorption)
-action of thiazide diuretics

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11
Q

aldosterone

A

stimulates Na reabsorption, K and H secretion

-in late DCT and collecting duct

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12
Q

ANP

A

inhibits Na reabsorption in medullary collecting duct

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13
Q

ADH

A

stimulates water reabsorption

-aquaporins in collecting duct

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14
Q

late distal tubule cation transport

A

large negative luminal potential

-driving force for H and K secretion by principal cells

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15
Q

aldosterone mechanism

A

in principal cells

  • increased sodium channels
  • increased Na/K ATPase in basolateral membrane
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16
Q

well-hydrated individuals

A

collecting duct impermeable to water

-low level aquaporins

17
Q

dehydrated individuals

A

collecting duct permeable to water

-high level of aquaporins

18
Q

ADH mechanism?

A

increase water permeability of late distal tubule and collecting duct

-via V2 receptors - leads to aquaporin

19
Q

too high of a blood flow in kidney?

A

will wash out concentration gradient

20
Q

countercurrent multiplier mechanism?

A

3 component:
descending and ascending limb of henle
vasa recta capillaries
collecting ducts

21
Q

vasa recta?

A

flows at slow rate, so it equilibrates with interstitium

too fast, washes out medullary interstitial gradient

  • pulls out solutes
  • due to increases renal blood flow
22
Q

what establishes medulla concentration gradient?

A

loop of henle
urea recycling

ADH causes urea reabsorption increase (dehydrated patient)

  • from inner medullary collecting duct**
  • recycled to vasa recta and loop of henle
23
Q

vasa recta importance?

A

maintain solute gradient

  • water and NaCl exchanged between descending and ascending limb
  • solute gradient maintained while small amounts of NaCl and water are returned to systemic circulation
24
Q

antidiuresis?

A

high ADH

makes collecting duct highly permeable to water and urea
-increase urea reabsorption allows even stronger gradient to pull out more water

low volume, concentrated urine

25
Q

ascending limb of henle?

A

diluting segment

26
Q

with ADH present

A

stronger medullary interstitial gradient

27
Q

early distal tubule?

A

very low osmolarity

as you go down collecting duct

  • pull out water and urea
  • concentrated urine
28
Q

diuresis?

A

low ADH
-no urea recycling (half gradient washed out)

as you go down collecting duct, not permeable to water

also have increased flow through collecting duct

have high volume of dilute urine

lower concentration in medullary interstitium**

29
Q

obligatory urine volume

A

have to put this much urine out to get rid of bodies waste

30
Q

clearance

A

U x V / P

can calculate osmolar clearance
C-osm = U-osm x V / P-osm

31
Q

free water clearance?

A

C-H2O = V - C-osm

total volume - osmolar clearance

negative - pure water retained
positive - pure water cleared from body

32
Q

U-osm vs. P-osm?

A

U < P pure water cleared (dilute urine)

U > P pure water retained (concentrated urine)

33
Q

fractional excretion

A

fraction of filtered load excreted in urine

34
Q

Fex = ? ***

A

U:x x P:cr / P:x x U:cr ***

of sodium - below 1% prerenal and AGN (glom)
above 2% ATN (tub), renal

35
Q

creatinine clearance

A

approximation of GFR

MSS Renal Exam 2 (7 decks)

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