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RENAL > IV: Urine-Concentrating Mechanism in the Inner Medulla > Flashcards

IV: Urine-Concentrating Mechanism in the Inner Medulla Flashcards

1
Q

Lack of water effects on plasma osmolarity, ADH and concentration of urine

A

Increased plasma osmolarity
Increase ADH
Concentrated urine = less volume

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2
Q

Excess water effect on plasma osmolarity, ADH, and urine concentration

A

Decreased plasma osmolarity
Decreased ADH
More diluted urine

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3
Q

ADH stimulates

A

Water reabsorption

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4
Q

Why is it dangerous to drink high V of water

A

Because of decreased plasma osmolarity

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5
Q

How do you prevent peeing overnight

A

There is ADH increase (increase in water reabsorption)

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6
Q

What occurs to ADH during dehydration, vomiting, diahrrea

A

Increase in plasma osmolarity

Increase in ADH

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7
Q

Function of Loop of Henle in concentrating/diluting urine

A

It generates + maintains an intersticial osmotic gradient

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8
Q

Osmotic gradient at renal cortex

A

290mOsm/Kg

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9
Q

Osmotic gradient at tip of medulla

A

1200 mOsm/kg

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10
Q

What does an increase in interstitial osmolarity do to the movement of H2O

A

It pulls the remaining H2O from descending structures

At loop of Henle 20% of H2O is reabsorbed

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11
Q

Descending limb is permeable/impermeable to H2O

A

Permeable

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12
Q

Ascending limb is permeable/impermeable to H2O

A

Impermeable

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13
Q

Concentration of tubular fluid as it descends limb

A

It becomes more concentrated as it loses H2O

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14
Q

Concentration of tubular fluid as it ascends the limb

A

It gets more diluted as it loses solutes

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15
Q

Where is the maximum osmotic gradient in loop of henle

A

At tip of medulla

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16
Q

Low osmotic gradient on ascending limb because

A

Na+ is diffusing out and due to impermeability no H2O can get in

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17
Q

Countercurrent multiplication used to

A

Generate an osmotic gradient to reabsorb H2O from descending tube and concentrate urine

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18
Q

Single effect in generating osmotic gradient

A

NaCl- are reabsorbed in descending loop = hyperosmolarized interstitium
This causes H2O in descending limb to passively diffuse into interstitium

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19
Q

Countercurrent multiplication, reabsorption of H2O is all

A

ADH DEPENDENT

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20
Q

Urea is produced by the

A

Liver

21
Q

From what is urea formed

A

NH4+

22
Q

How is urea filtrated in glomerulus

A

Freely filtrates

23
Q

Where is part of urine reabsorbed

A

In proximal tubule

24
Q

In thin limb of loop of henle, urea is

A

Secreted from interstitium to renal tubule

25
Q

What transporter is used for urea to get to loop of henle

A

UT-A2

26
Q

What part is impermeable to urea

A

Thick ascending loop of henle

27
Q

UT-A1 and UT-A3 location and function

A

At medullary collecting duct and allow PASSIVE reabsorption of urea into interstitium

28
Q

Urea reabsoprtion is ADH dependent?

A

Yes

29
Q

% of urea contribution to osmolarity of medullary interstitium

A

40-50%

30
Q

Is urea reabsorbed along with H2O in distal tubule and cortical collecting duct?

A

No

31
Q

How does interstitial osmolarity reach 1200mOsm/KL at tip of medulla?

A

Due to urea recycling

32
Q

Blood flow of vasa recta

A

Opposite to tubular flow

33
Q

Function of vasa recta

A

Prevent absorbed H2O from diluting the interstitium

H2O passes directly to vasa recta

34
Q

Another reason, H2O related, of why medullary osmolarity reaches 1200mOsm/KL

A

Because H2O directly crosses to vasa recta so it does not dilute the interstitium

35
Q

Where is ADH synthesized

A

In hypothalamo

36
Q

When is ADH synthetised

A

Increase plasma osmolarity (decreased H2O concentration)

Decreased blood pressure (Dehydration, hemorrhage)

37
Q

Which receptors and organs sense changes in plasma osmolarity and blood pressure

A

V1 and V2 receptors in vascular smooth muscle

And kidney

38
Q

Where are V2 receptors located

A

In kidney in basolateral membrane of principal cells

39
Q

What allows reabsorption of H2O

A

AQP2 which are driven by increase in interstitial osmolarity (decrease of water)

40
Q

What does ADH stimulate in thick ascending limb

A 
Urea reabsorption (UT-A2)
Na+ transport
41
Q 
W/ ADH 
Urea:
Volume:
H2O:
Osmolarity:
A

Less urea
Decreased volume
Decreased H2O
Higher osmolarity

42
Q 
W/O ADH
Urea:
Volume:
H2O:
Osmolarity:
A

Increased urea
Increased volume
Increased H2O
Decreased osmolarity

43
Q

ADH Control: increase in osmolarity (sensor receptor)

A

Increase in osmolarity = decreased H2O (we need more ADH)

OSMORECEPTORS in hypothalamus

44
Q

ADH Control: Decreased blood pressure

A

We need more ADH

Baroceptors in atrium and carotid arch

45
Q

Water loss tightly regulated by

A

ADH

46
Q

How much do adults eliminate from catabolism

A

600mOsm/d

47
Q

Maximum concentration of urine

A

1200mOsm/d

0.5L/d

48
Q

Mechanism to ensure that we lose a min. amount of liquid a day

A

Thirst mechanism

49
Q

Main mechanism to control [Na+] and osmolarity

A

ADH and thirst

RENAL (9 decks)

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