P is a small, round, reddish structure located on the dorsal side of forebrain. It contains a stalk-and releases a hormone Q which controls diurnal rhythm of the body. P and Q are

Options

A. Hypothalamus, MSH respectively
B. Pineal gland, melanin respectively
C. Pineal gland, melatonin respectively
D. Pituitary gland, MSH respectively

Answer

**Step-by-Step Solution:**

1. **Identify Structure P**: The question describes a small, round, reddish structure located on the dorsal side of the forebrain. This structure is known as the pineal gland.

2. **Location of the Pineal Gland**: The pineal gland is situated on the dorsal side of the forebrain, which is an important anatomical detail.

3. **Function of the Pineal Gland**: The pineal gland is responsible for the secretion of a hormone that regulates various bodily rhythms, particularly the diurnal rhythm.

4. **Identify Hormone Q**: The hormone released by the pineal gland that controls the diurnal rhythm is melatonin.

5. **Role of Melatonin**: Melatonin plays a crucial role in regulating the sleep-wake cycle, body temperature, and overall circadian rhythms. It also influences metabolism, pigmentation, and immune defense.

6. **Conclusion**: Therefore, P is the pineal gland and Q is melatonin.

**Final Answer**: P is the pineal gland and Q is melatonin.

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