Question

Which of the following statement/statements is/are incorrect?
I) ADH is released if blood has low osmolarity.
II) ADH is released if blood has high osmolarity.
III) Aldosterone facilitates water reabsorption.
IV) ANF causes vasoconstriction.
V) ADH increases water reabsorption.

• A. I, IV, and V only
• B. I and IV only
• C. I and III only
• D. IV only

Answer 1

The correct option is B I and IV only

Antidiuretic hormone (vasopressin) is released by the posterior pituitary lobe when the blood has high osmolarity (number of solute particles per litre of solution). It plays a role in reducing blood osmolarity by increasing reabsorption of water in distal convoluted tubule (DCT) and collecting duct of the nephron.

When the blood volume and blood pressure decrease, juxtaglomerular cells in the kidneys secrete the enzyme renin. Renin catalyzes the conversion of angiotensinogen to angiotensin II. Angiotensin II stimulates the adrenal cortex to release aldosterone. Aldosterone promotes the absorption of NaCl and water from DCT.

An increase in blood volume and blood flow to the atria of the heart causes the release of a hormone called atrial natriuretic factor (ANF). This hormone stimulates vasodilation i.e. dilation of blood vessels and not vasoconstriction i.e. narrowing of blood vessels. This in turn decreases the blood pressure and helps in maintaining GFR.