Diuresis is the condition in which

Options

A. the excretory volume of urine increases
B. the excretory volume of urine decreases
C. the kidneys fail to excrete urine
D. the water balance of the body is disturbed.

Answer

**Step-by-Step Solution:**

1. **Understanding Diuresis**: Diuresis is a condition characterized by an increase in urine output. This can occur due to various physiological factors, but a key mechanism involves the hormone ADH (antidiuretic hormone).

2. **Role of ADH**: ADH is produced in the hypothalamus and released from the posterior pituitary gland. It plays a crucial role in regulating water balance in the body by increasing water reabsorption in the kidneys.

3. **Water Intake and Plasma Osmolality**: When there is an increase in water intake, the plasma osmolality (the concentration of solutes in the blood) decreases. This is because the excess water dilutes the solutes present in the plasma.

4. **Inhibition of Osmoreceptors**: The decrease in plasma osmolality inhibits the osmoreceptors located in the anterior hypothalamus. These osmoreceptors are responsible for sensing changes in blood osmolality.

5. **Decrease in ADH Secretion**: As a result of the inhibited osmoreceptors, the secretion of ADH from the posterior pituitary gland decreases. With lower levels of ADH, the kidneys are less able to reabsorb water.

6. **Decreased Water Permeability**: The decrease in ADH leads to reduced water permeability in the distal tubules and collecting ducts of the kidneys. This means that less water is reabsorbed back into the bloodstream.

7. **Increased Urine Output**: Due to the decreased reabsorption of water, there is an increase in urine volume and urine osmolality. The kidneys excrete more water, leading to a higher urinary output.

8. **Conclusion**: Therefore, diuresis is defined as the condition in which there is an increase in urinary output due to decreased ADH levels, resulting in reduced water reabsorption in the kidneys.

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