Kidney Function TBL

Question 1

If a patient is dehydrated, the filtrate present in which of these areas will have highest osmolarity:
Bowman’s capsule
Tip of loop of Henle
Before DCT
Start of medullary collecting duct

Answer 1

Tip of loop of henle
Passive loss of water but salt remains in

Question 2

Why do most diuretics increase potassium excretion?:
They reduce uptake by Na/K/Cl transporter
The increase in sodium in the distal nephron is exchanged for potassium in the collecting duct because of change in membrane potential
The increase in flow rate is detected in the collecting duct and directly stimulates potassium excretion
They cause a rise in plasma pH and this stimulates potassium excretion

Answer 2

The increase in flow rate is detected in the collecting duct and directly stimulates potassium excretion

Question 3

The urine samples of different patients were analysed using the urine osmolarity test. Whose sample is likely to have the highest osmolarity?
Patient with loss-of-function V2 receptor mutation
Patient suffering from central diabetes insipidus
Patient with loss-of-function UT-B1 urea transporter mutation
Patient suffering from hepatic cirrhosis

Answer 3

Patient suffering with hepatic cirrhosis

Question 4

An athlete after finishing their London Marathon run drank 2L of distilled water. Which of the following statement is correct about their body fluids?
Decrease in Extracellular Fluid (ECF) volume.
Decrease in plasma osmolarity
Decrease in Intracellular Fluid osmolarity
Decrease in interstitial fluid volume

Answer 4

Decrease in plasma osmolarity

Question 5

The increase in plasma concentration of which solute will have no effect on ADH production?
Glucose
Urea
Salt
Ethanol

Answer 5

Urea

Question 6

Sodium excretion is very limited (less than 1% of filtered load) and several mechanisms exist to tightly regulate it. Increasing sodium excretion reduces water retention. Potassium excretion can vary over a very large range (from 1 to 80% of filtered load). Why doesn’t this variability in potassium excretion have a marked effect on water balance?
Potassium is only excreted in the distal nephron so there is no time for it to have an effect on osmolarity.

Potassium is a major intracellular ion, so the variability affects intra-cellular fluid volume not extracellular fluid volume.

The amount of potassium in the plasma and extracellular is much lower than the amount sodium so that variations in this amount are insufficient to have a marked effect on water balance.

Whilst the amount of potassium in the tubular fluid in the collecting duct varies its concentration does not so it does not affect osmolarity.

Answer 6

The amount of potassium in the plasma and extracellular is much lower than the amount sodium so that variations in this amount are insufficient to have a marked effect on water balance.

Question 7

Why do most diuretics increase potassium excretion?
They reduce the uptake of K+ by the Na/K/Cl transporter.
The increase in sodium in the distal nephron is exchanged for potassium in the collecting duct because of the change in membrane potential.
The increase in flow rate is detected in the collecting duct and directly stimulates potassium excretion.
They cause a rise in plasma pH and this stimulates potassium export.

Answer 7

The increase in flow rate is detected in the collecting duct and directly stimulates potassium excretion.