You and your study partner want of draw the pathway that controls the controls the reabsorption of sodium ion when blood pressure falls. Which of the following is the correct sequence of events ?
(a) Aldosterone is released
(b) Kidney tubules reabsorb `Na^(+)`
(c ) Renin is released
(d) Juxtaglomerular apparatus (JOA) recognizes a drop in blood pressure.
(e ) Angiotensin II is produced

Options

A. a,c,e,b,d
B. b,d,c,a,e
C. d,c,e,a,b
D. b,d,c,a,e

Answer

To determine the correct sequence of events that control the reabsorption of sodium ions when blood pressure falls, we can break down the process into the following steps:

1. **Juxtaglomerular Apparatus (JGA) Recognizes a Drop in Blood Pressure**: The process begins when the juxtaglomerular apparatus in the kidneys detects a decrease in blood pressure or blood volume. This recognition is critical as it triggers the subsequent events.

2. **Renin is Released**: In response to the drop in blood pressure, the juxtaglomerular cells secrete an enzyme called renin into the bloodstream. Renin plays a crucial role in the conversion of angiotensinogen to angiotensin I.

3. **Angiotensin II is Produced**: Renin acts on angiotensinogen (a protein produced by the liver) and converts it into angiotensin I. Angiotensin I is then converted into angiotensin II by the action of the angiotensin-converting enzyme (ACE), primarily in the lungs. Angiotensin II is a potent vasoconstrictor and also stimulates the adrenal cortex.

4. **Aldosterone is Released**: Angiotensin II stimulates the adrenal cortex to release aldosterone, a hormone that plays a key role in regulating sodium and water balance in the body.

5. **Kidney Tubules Reabsorb Na⁺**: Finally, aldosterone acts on the kidney tubules, specifically the distal convoluted tubule (DCT) and collecting ducts, promoting the reabsorption of sodium ions (Na⁺) back into the bloodstream. This reabsorption helps to increase blood volume and, consequently, blood pressure.

Thus, the correct sequence of events is:
(d) Juxtaglomerular apparatus recognizes a drop in blood pressure → (c) Renin is released → (e) Angiotensin II is produced → (a) Aldosterone is released → (b) Kidney tubules reabsorb Na⁺.

### Final Sequence:
1. (d) Juxtaglomerular apparatus recognizes a drop in blood pressure.
2. (c) Renin is released.
3. (e) Angiotensin II is produced.
4. (a) Aldosterone is released.
5. (b) Kidney tubules reabsorb Na⁺.