Vasopressin released from the neurohypophysis is mainly responsible for

Options

A. facultative reabsorption of water through Henle’s loop
B. obligatory reabsorption of water through Bowman’s capsule
C. Facultative reabsorption to water through DCT
D. obligatory reabsorption of water through PCT

Answer

### Step-by-Step Solution

1. **Understanding Vasopressin (ADH)**:
- Vasopressin, also known as Antidiuretic Hormone (ADH), is a hormone produced in the hypothalamus and released from the neurohypophysis (posterior pituitary).
- Its primary function is to regulate water balance in the body by promoting water reabsorption in the kidneys.

2. **Identifying the Function of Vasopressin**:
- Vasopressin acts on the kidneys to reduce water loss by increasing water reabsorption.
- It specifically targets the nephrons, which are the functional units of the kidney.

3. **Locating the Sites of Action in the Nephron**:
- The nephron consists of several parts:
- Bowman's capsule
- Proximal Convoluted Tubule (PCT)
- Loop of Henle
- Distal Convoluted Tubule (DCT)
- Collecting Duct
- Vasopressin primarily acts on the DCT and the collecting duct.

4. **Understanding Reabsorption Types**:
- **Obligatory Reabsorption**: This occurs in the PCT and is independent of ADH; it happens regardless of the body's hydration status.
- **Facultative Reabsorption**: This occurs in the DCT and collecting duct and is dependent on the presence of ADH. This means that water reabsorption can be adjusted based on the body's needs.

5. **Conclusion**:
- Since vasopressin (ADH) promotes facultative reabsorption of water in the DCT and collecting duct, the correct answer to the question is that vasopressin is mainly responsible for **facultative reabsorption of water through the DCT**.

### Final Answer:
Vasopressin released from the neurohypophysis is mainly responsible for **facultative reabsorption of water through the DCT**.

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