IV: Urine-Concentrating Mechanism in the Inner Medulla

Question 1

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

Answer 1

Increased plasma osmolarity
Increase ADH
Concentrated urine = less volume

Question 2

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

Answer 2

Decreased plasma osmolarity
Decreased ADH
More diluted urine

Question 3

ADH stimulates

Answer 3

Water reabsorption

Question 4

Why is it dangerous to drink high V of water

Answer 4

Because of decreased plasma osmolarity

Question 5

How do you prevent peeing overnight

Answer 5

There is ADH increase (increase in water reabsorption)

Question 6

What occurs to ADH during dehydration, vomiting, diahrrea

Answer 6

Increase in plasma osmolarity

Increase in ADH

Question 7

Function of Loop of Henle in concentrating/diluting urine

Answer 7

It generates + maintains an intersticial osmotic gradient

Question 8

Osmotic gradient at renal cortex

Answer 8

290mOsm/Kg

Question 9

Osmotic gradient at tip of medulla

Answer 9

1200 mOsm/kg

Question 10

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

Answer 10

It pulls the remaining H2O from descending structures

At loop of Henle 20% of H2O is reabsorbed

Question 11

Descending limb is permeable/impermeable to H2O

Answer 11

Permeable

Question 12

Ascending limb is permeable/impermeable to H2O

Answer 12

Impermeable

Question 13

Concentration of tubular fluid as it descends limb

Answer 13

It becomes more concentrated as it loses H2O

Question 14

Concentration of tubular fluid as it ascends the limb

Answer 14

It gets more diluted as it loses solutes

Question 15

Where is the maximum osmotic gradient in loop of henle

Answer 15

At tip of medulla

Question 16

Low osmotic gradient on ascending limb because

Answer 16

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

Question 17

Countercurrent multiplication used to

Answer 17

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

Question 18

Single effect in generating osmotic gradient

Answer 18

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

Question 19

Countercurrent multiplication, reabsorption of H2O is all

Answer 19

ADH DEPENDENT

Question 20

Urea is produced by the

Answer 20

Liver

Question 21

From what is urea formed

Answer 21

NH4+

Question 22

How is urea filtrated in glomerulus

Answer 22

Freely filtrates

Question 23

Where is part of urine reabsorbed

Answer 23

In proximal tubule

Question 24

In thin limb of loop of henle, urea is

Answer 24

Secreted from interstitium to renal tubule

Question 25

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

Answer 25

UT-A2

Question 26

What part is impermeable to urea

Answer 26

Thick ascending loop of henle

Question 27

UT-A1 and UT-A3 location and function

Answer 27

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

Question 28

Urea reabsoprtion is ADH dependent?

Answer 28

Yes

Question 29

% of urea contribution to osmolarity of medullary interstitium

Answer 29

40-50%

Question 30

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

Answer 30

No

Question 31

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

Answer 31

Due to urea recycling

Question 32

Blood flow of vasa recta

Answer 32

Opposite to tubular flow

Question 33

Function of vasa recta

Answer 33

Prevent absorbed H2O from diluting the interstitium | H2O passes directly to vasa recta

Question 34

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

Answer 34

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

Question 35

Where is ADH synthesized

Answer 35

In hypothalamo

Question 36

When is ADH synthetised

Answer 36

Increase plasma osmolarity (decreased H2O concentration) | Decreased blood pressure (Dehydration, hemorrhage)

Question 37

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

Answer 37

V1 and V2 receptors in vascular smooth muscle | And kidney

Question 38

Where are V2 receptors located

Answer 38

In kidney in basolateral membrane of principal cells

Question 39

What allows reabsorption of H2O

Answer 39

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

Question 40

What does ADH stimulate in thick ascending limb

Answer 40

``` Urea reabsorption (UT-A2) Na+ transport ```

Question 41

``` W/ ADH Urea: Volume: H2O: Osmolarity: ```

Answer 41

Less urea Decreased volume Decreased H2O Higher osmolarity

Question 42

``` W/O ADH Urea: Volume: H2O: Osmolarity: ```

Answer 42

Increased urea Increased volume Increased H2O Decreased osmolarity

Question 43

ADH Control: increase in osmolarity (sensor receptor)

Answer 43

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

Question 44

ADH Control: Decreased blood pressure

Answer 44

We need more ADH | Baroceptors in atrium and carotid arch

Question 45

Water loss tightly regulated by

Answer 45

ADH

Question 46

How much do adults eliminate from catabolism

Answer 46

600mOsm/d

Question 47

Maximum concentration of urine

Answer 47

1200mOsm/d | 0.5L/d

Question 48

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

Answer 48

Thirst mechanism

Question 49

Main mechanism to control [Na+] and osmolarity

Answer 49

ADH and thirst