Mechanism to Adjust Urine Concentration

Question 1

How does a loop diuretic work?

Answer 1

It books the Na/K, Cl cotransporter in the TAL and thus it’s disturbing the multiplier system and thus cannot concentrate the urine. Therefore, pts loose a huge amount of Na and thus water.

Question 2

What are some problems that can arise due to the body’s inability to control Salt and Water Balance?

Answer 2

1. Edema
2. Disorders of plasma K concentration: hypo or hyperkalemia
3. Undesirable changes in blood pressure
4. Acid/base disorders
5. Neurological problems: shrinking or swelling of the brain

Question 3

In the PCT name ways Na is reabsorbed.

Answer 3

1. Cotransport with glu, AA, phosphate
2. Na/H exchange (countertransport)
3. Straight Na channels (minor)
   4.

Question 4

What transports are taking place in the Thin descending limb?

Answer 4

No active transport occurs here. Reabsorption of water is the main thing that happens here, and is impermeable to most solutes. Epithelium is permeable to water and small ions.

Question 5

What transporters are found on the thick ascending limb?

Answer 5

main one is Na/K/2Cl symporter. It’s impermeable to water. thus called the diluter.

Question 6

What are some example of loop diuretics?

Answer 6

Furosemide, bumetanide

Question 7

What is the permeability of DCT?

Answer 7

1 Permeability for water depends on ADH.
2. Permeability to electrolytes is very low = low conductance thus requires a HIGH electrochemical gradient to drive ion transport

Question 8

What kind of transport (low/high conductance; high or low gradient) are you likely to find in the DCT?

Answer 8

Low conductance, high gradient. It uses a lot of energy (has more Na/K-ATPase than PCT) maintain a strong enough gradient to drive even more Na out of the tubular fluid.

Question 9

What’s the main transporter at the DCT?

Answer 9

Na/Cl symporter

Question 10

What does thiazide inhibit and where does it act?

Answer 10

Inhibits Na/Cl symporter and acts on the DCT.

Question 11

In the TAL, what creates the gradient for Ca and Phosphate to get reabsorbed?

Answer 11

K being pushed out of the cell down it’s concentration gradient via the leaky K channels.

Question 12

Where does final regulation of Na and water occur?

Answer 12

Late DCT.

Question 13

Aldosterone works to increase Na reabsorption in principal cells by inserting what types of channels on the apical and basolateral sides?

Answer 13

Apical side: Na channels

Basolateral: Na/K ATPase

Question 14

What parts of the nephron are principal cells found?

Answer 14

late DCT and CD

Question 15

What are the functions of principal cells?

Answer 15

Na reabsorption, K secretion, water reabsorption

Question 16

What are the functions of a-intercalated cells?

Answer 16

K reabsorption and H secretion

Question 17

The permeability of water in both the DCT and Collecting tubules are dependent on _?

Answer 17

ADH

Question 18

What are the three components of the countercurrent multiplier mechanism?

Answer 18

1. Descending ascending limb
2. Casa recta
3. Collecting ducts

Question 19

What happens to your ability to concentrate your urine with a high protein diet?

Answer 19

You are able to concnetrate your urine even further due to the breakdown products of protein being urine.

Question 20

In the countercurrent multiplier mechnaism, what is the function of vasa recta?

Answer 20

Maintains solute gradient

Question 21

WHat would happen to your urine concentration ability if you were given a drug that increase blood flow through the peritubular capillary?

Answer 21

The concentration ability of the kidney would decrease as the increased blood flow increase pressure.

Question 22

What is obligatory urine volume?

Answer 22

The minimum amount of urine you have to excrete in order to eliminate the waste generated in the body during a day.

Question 23

How do you calculate how much water is needed to eliminate the amount of waste produced?

Answer 23

About of waste produced divided by the total concentration. e.g 600 (daily waste) / 1200 (what the total concentration of urine/ intersitum is)

Question 24

What is a major drawback for diuretics?

Answer 24

Diuretics decreases the body’s ability to concentrate urine to the max as dilute urine is excreted. Therefore the body has to excrete out larger volume of water to eliminiate all the waste produced.

Question 25

What is Osmolar clearance?

Answer 25

The plasma volume cleared of osmoles (solutes) each minute. Its the difference between the urine flow and the free water clearance.

Question 26

By calculating osmolar clearance, we are estimating the renal capacity to do what?

Answer 26

Excrete solutes.

Question 27

What is the equation for osmolar clearance ?

Answer 27

C(osm) = Usom x (V/Poms)

essentially it’s the same equation as clearance

Question 28

What is free water clearance?

Answer 28

The difference between urine flow and osmolar clearance.

Question 29

Free water clearance is positive when _?

Answer 29

Excess water is excreted compared to solutes. Pure water was excreted.

Question 30

Free water clearance is negative when _?

Answer 30

Excess solutes are excreted compared to water. Pure water is retained

Question 31

Free water clearance measures the renal capacity to do what?

Answer 31

Excrete solute-free water

Question 32

What is the equation for Free water clearance?

Answer 32

C(h20) = V - Cosm

Question 33

How does ADH affect CH20?

Answer 33

Decrease since ADH causes water to be retained.

Question 34

What is the fractional excretion?

Answer 34

The fraction (percentage) of filtered load of a substance that is excreted in urine.

Question 35

What is the equation for fractional excretion?

Answer 35

Amount excreted / Amount filtered (filtered load).

[Ux] V / P x GFR

Question 36

What does fractional excretion below 1% indicate?

Answer 36

prerenal problems.

Question 37

What does fractional excretion greater 2% indicate?

Answer 37

Renal problem