Question

Which of the following statements regarding antidiuretic hormone is false?

A. It is also called vasopressin

B. It increases water reabsorption by the kidney

C. An increase in plasma osmolarity can stimulate its release

D. A decrease in blood volume or blood pressure can stimulate its release

E. Its target cells are found in the proximal convoluted tubule of a nephron

Answer 1

Answer) option E - Its target cells are found in the proximal convoluted tubule of nephron

Explanation - As the main targets cells of antidiuretic hormone are present in the distal convoluted tubule and collecting duct of nephron.

Antidiuretic harmone increases permeability of distal convoluted tubule and collecting duct to water by increasing the pore size through aquaporin-2 channels, then it increases water reabsorption. So that plasma osmolarity decreases and urine osmolarity increases.

Explanation for other options -

- option A-yes, antidiuretic hormone is also called vasopressin. As high doses of antidiuretic hormone via vasopressin receptors, it produces peripheral vasoconstriction due to vasoconstricting effect and finally it increases blood pressure, because of this reason antidiuretic hormone is also called vasopressin.

-option B- yes, antidiuretic increases water reabsorption by the kidneys as it increases the water permeability of distal convoluted tubule and collecting duct to water by increasing the pore size via aquaporin-2 channels and causes increased water reabsorption by the kidneys and decreased water excretion from the kidneys.

-option C-yes, an increase in plasma osmolarity can stimulates its release. As increase in plasma osmolarity directly stimulate osmoreceptors in the hypothalamus,the impulses from the hypothalamus travel via hypothalamo-hypophysial tract to reach posterior pituitary gland and increases the antidiuretic hormone secretion.

-option D- yes, a decrease in blood volume and blood pressure stimulates its release. As decrease in effective circulating blood volume and blood pressure causes decreased baroreceptor activity, which stimulates osmoreceptors and releases the antidiuretic hormone from the posterior pituitary gland.