Question

Angiotensin–II increases blood volume by –

• A. By stimulating release of ADH
• B. Signaling $\text{PCT}$ to reabsorb more $\text{NaCl}$ and ${\text{H}}_2\text{O}$
• C. Stimulating kidney to release renin
• D. Both $\text{(1)}$ and $\left(2\right)$

Answer 1

The correct option is D Both $\text{(1)}$ and $\left(2\right)$

A fall in glomerular blood flow/glomerular blood pressure/$\text{GFR}$ can activate the $\text{JG}$ cells to release renin which converts angiotensinogen in blood to angiotensin $\text{I}$ and further to angiotensin $\text{II}$. Angiotensin $\text{II}$, being a powerful vasoconstrictor, increases the glomerular blood pressure and thereby $\text{GFR}$. Angiotensin $\text{II}$ also stimulates the reabsorption of salts and water from the PCT. Angiotensin $\text{II}$ activates the adrenal cortex to release Aldosterone. Aldosterone causes reabsorption of and water from the distal parts of the tubule. This also leads to an increase in blood pressure and $\text{GFR}$. This complex mechanism is generally known as the Renin-Angiotensin mechanism.
So, the correct answer is option 'd'.