Which of the following acts as a check on RAAS?

Options

A. ANF
B. Aldosterone
C. ACE
D. Renin

Answer

To solve the question "Which of the following acts as a check on RAAS?", we need to understand the components of the Renin-Angiotensin-Aldosterone System (RAAS) and identify which factor regulates or inhibits this system.

### Step-by-Step Solution:

1. **Understand RAAS**:
- RAAS stands for Renin-Angiotensin-Aldosterone System. It is a hormone system that regulates blood pressure and fluid balance in the body.

2. **Components of RAAS**:
- **Renin**: An enzyme secreted by the kidneys when blood pressure drops.
- **Angiotensinogen**: A protein produced by the liver that is converted to angiotensin I by renin.
- **Angiotensin I**: Converted to angiotensin II by the Angiotensin Converting Enzyme (ACE) found in the lungs.
- **Angiotensin II**: A potent vasoconstrictor that increases blood pressure and stimulates the secretion of aldosterone from the adrenal glands.

3. **Role of Aldosterone**:
- Aldosterone promotes the reabsorption of sodium and water in the kidneys, which increases blood volume and blood pressure.

4. **Check on RAAS**:
- The system is primarily checked by the **Atrial Natriuretic Factor (ANF)**, which is released from the heart. ANF counteracts the effects of RAAS by promoting the excretion of sodium and water, thus lowering blood pressure.

5. **Conclusion**:
- The factor that acts as a check on RAAS is **Atrial Natriuretic Factor (ANF)**.

### Final Answer:
The correct option is **Atrial Natriuretic Factor (ANF)**.

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