Which of the following statement is correct?

Options

A. ANF and renin-angiotensin mechanism are similar in their function
B. ADH and ANF are vasodilators
C. Vasopressin prevents more loss of water through urine
D. JGA releases renin when gromerular blood pressure increases

Answer

To determine which statement is correct among the given options regarding the human excretory system, we can analyze each statement step by step.

### Step-by-Step Solution:

1. **Understanding ANF and Renin-Angiotensin Mechanism:**
- **ANF (Atrial Natriuretic Factor)** is a hormone released from the atria of the heart that helps to lower blood pressure by promoting vasodilation and increasing sodium and water excretion.
- **Renin** is secreted by the juxtaglomerular apparatus (JGA) of the kidneys when blood pressure is low. It initiates the renin-angiotensin-aldosterone system (RAAS), which ultimately increases blood pressure.

**Analysis of Statement A:**
- The statement claims that ANF and the renin-angiotensin mechanism are similar in their functions. This is incorrect because ANF decreases blood pressure while the renin-angiotensin mechanism increases blood pressure.

**Conclusion:** Statement A is incorrect.

2. **Analyzing ADH and ANF:**
- **ADH (Antidiuretic Hormone)**, also known as vasopressin, is produced in the hypothalamus and released from the posterior pituitary. Its primary function is to promote water reabsorption in the kidneys, thus reducing urine output and increasing blood volume.
- ANF, as mentioned, is a vasodilator that decreases blood pressure.

**Analysis of Statement B:**
- The statement claims that ADH and ANF are both vasodilators. This is incorrect because ADH primarily acts as a vasoconstrictor (though its main role is water retention), while ANF is a vasodilator.

**Conclusion:** Statement B is incorrect.

3. **Evaluating the Role of Vasopressin:**
- As stated, vasopressin (ADH) prevents excessive water loss through urine by acting on the distal convoluted tubule (DCT) and collecting ducts of the nephron, promoting water reabsorption.

**Analysis of Statement C:**
- The statement claims that vasopressin prevents more loss of water through urine. This is correct, as the main function of ADH is to conserve water.

**Conclusion:** Statement C is correct.

4. **Understanding JGA and Renin Release:**
- The JGA releases renin in response to low blood pressure, not when it increases. Renin catalyzes the conversion of angiotensinogen to angiotensin I, which is then converted to angiotensin II, leading to increased blood pressure.

**Analysis of Statement D:**
- The statement claims that JGA releases renin when glomerular blood pressure increases. This is incorrect because renin is released when blood pressure decreases.

**Conclusion:** Statement D is incorrect.

### Final Answer:
The correct statement is **C: Vasopressin prevents more loss of water through urine.**

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