What will happen when excessive loss of fluid from the body then? -

Options

A. (1) activates receptors which stimulates the hypothalamus to release ADH from the neuro hypophysis
B. (2) osmoreceptors switch off and secretion of vasopressin reduces
C. (3) release of aldosterone from adrenal medulla
D. (4) angiotensinogen is converted into angiotensin-I

Answer

### Step-by-Step Solution:

1. **Understanding Fluid Loss**: Excessive loss of fluid from the body can occur due to various reasons such as dehydration, excessive urination, sweating, or diarrhea. This loss can lead to a decrease in blood volume and changes in the concentration of body fluids.

2. **Role of Osmoreceptors**: The body has specialized receptors known as osmoreceptors that detect changes in blood volume and ionic concentration. When fluid loss occurs, these receptors are activated due to the increase in osmolarity (concentration of solutes in the blood).

3. **Activation of the Hypothalamus**: Once the osmoreceptors detect the changes, they send signals to the hypothalamus. The hypothalamus is a crucial part of the brain that helps regulate various bodily functions, including fluid balance.

4. **Release of ADH (Vasopressin)**: In response to the signals from the osmoreceptors, the hypothalamus stimulates the release of Antidiuretic Hormone (ADH), also known as vasopressin. This hormone is released from the posterior pituitary gland (neurohypophysis).

5. **Action of ADH**: ADH acts primarily on the kidneys, specifically on the distal convoluted tubules and collecting ducts. It increases the permeability of these tubules to water, allowing more water to be reabsorbed back into the bloodstream.

6. **Maintaining Fluid Balance**: The reabsorption of water helps to conserve body fluids, restore blood volume, and dilute the concentration of solutes in the blood, thereby maintaining homeostasis.

7. **Conclusion**: Therefore, the excessive loss of fluid from the body activates osmoreceptors, which in turn stimulates the hypothalamus to release ADH. This process is crucial for regulating water balance in the body.