Arrange the following events occuring in Renin-Angiotensin mechanism in the correct order:

A. Increase in blood pressure and Glomerular filtration rate

B. Reabsorption of $\mathrm{Na}^+$ and water from distal parts of tubule due to Aldosterone

C. Fall in Glomerular filtration rate

D. Vasoconstriction by Angiotensin II and release of Aldosterone.

E. Renin converts Angiotensinogen into Angiotensin I, followed by Angiotensin II.

Choose the correct answer from the options given below:

Question

Arrange the following events occuring in Renin-Angiotensin mechanism in the correct order:

A. Increase in blood pressure and Glomerular filtration rate

B. Reabsorption of $\mathrm{Na}^+$ and water from distal parts of tubule due to Aldosterone

C. Fall in Glomerular filtration rate

D. Vasoconstriction by Angiotensin II and release of Aldosterone.

E. Renin converts Angiotensinogen into Angiotensin I, followed by Angiotensin II.

Choose the correct answer from the options given below:

Accepted Answer

D. 1. **Understand the trigger for this pathway:** The renin-angiotensin mechanism is activated when blood flow to the kidney drops.

Given a drop in blood volume or pressure, the glomerular filtration rate falls, which corresponds to event **C**.

2. **Identify the kidney's response to low GFR:** The juxtaglomerular (JG) cells sense this fall and release the enzyme renin, which converts angiotensinogen (from blood) into angiotensin I, and this is further converted into angiotensin II.

So, this step corresponds to event **E**.

3. **Determine the action of angiotensin II:** Angiotensin II is a powerful vasoconstrictor and also stimulates the adrenal cortex to release aldosterone.

Hence, this matches event **D**.

4. **Follow the effect of aldosterone:** Aldosterone acts on the distal parts of the nephron tubule, causing reabsorption of $\mathrm{Na}^+$ and water back into the blood.

Therefore, this corresponds to event **B**.

5. **Conclude the final outcome:** This reabsorption of sodium and water restores blood volume, raising both blood pressure and the glomerular filtration rate.

So, the final event is **A**.

6. **Final sequence:** Putting these steps together gives the order **C, E, D, B, A**.

Hence, the correct answer is **Option D**.