Session 4 - Control Of Plasma Volume

Question 1

In what ways in sodium excreted from the body?

Answer 1

Urine
Faeces
Sweat

Question 2

In which part of the nephron does no sodium reabsorption occur?

Answer 2

Descending thin limb of the loop of Henle

Question 3

In which parts of the nephron does no water reabsorption occur?

Answer 3

Ascending limb of the loop of Henle

Distal convoluted tubule

Question 4

Where in the nephron does sodium reabsorption occur?

Answer 4

Proximal tubule (67%)
Ascending limb of the loop of Henle (25%)
Distal convoluted tubule (~5%)
Collecting duct (3%)

Question 5

Where in the nephron does water reabsorption occur?

Answer 5

Proximal tubule (65%)
Thin descending limb of the loop of Henle (10-15%)
Collecting duct (5% during water loading, 25% during dehydration)

Question 6

Explain how an increase in renal artery blood pressure leads to natriuresis and diuresis.

Answer 6

When renal artery blood pressure increases, there is reduced number of Na-H antiporters in the proximal tubule and reduced activity of Na-K ATPase in the proximal tubule. This causes a reduction in sodium reabsorption in the proximal tubule and therefore a reduction in water reabsorption. Therefore there is increased sodium and water excretion, creating pressure natriuresis and diuresis.

Question 7

Sodium reabsorption is mainly an active processs, what drives its reuptake?

Answer 7

Na-K-ATPase pumps on the basolateral membrane

Question 8

Name the different sodium transporters present on the apical membrane of the proximal tubule.

Answer 8

Na-H antiporter
Na-Glucose symporter
Na-Amino Acid symporter
Na-Urea symporter
Na-Pi symporter

Question 9

Name the sodium transporter present in the apical membrane of the thick ascending limb of the loop of Henle.

Answer 9

Na-K-Cl cotransporter (NaKCC2)

Question 10

Name the sodium transporter present in early distal tubule.

Answer 10

NaCl symporter

Question 11

Name the sodium channel present in the late distal tubule and the collecting duct.

Answer 11

Epithelial sodium channel (ENaC)