Suprachiasmatic nucleus is influenced by

Options

A. increased light intensity
B. decreased light intensity
C. Both of the above
D. None of the Above

Answer

**Step-by-Step Solution:**

1. **Understand the Suprachiasmatic Nucleus (SCN)**: The SCN is a small region in the brain located in the hypothalamus. It is known as the body's primary circadian clock, regulating the sleep-wake cycle and other circadian rhythms.

2. **Identify the Location**: The SCN is situated near the optic chiasm, where the optic nerves from the eyes cross. This location is crucial because it allows the SCN to receive direct input from the eyes.

3. **Light Influence on SCN**: The SCN is highly sensitive to light. It receives signals about light intensity from the retina through the retinohypothalamic tract. Increased light intensity signals the SCN to promote wakefulness and alertness.

4. **Evaluate the Options**:
- **Option 1: Increased light intensity** - This is correct as the SCN is directly influenced by light, particularly increased light.
- **Option 2: Decreased light intensity** - While the SCN can respond to decreased light, it is primarily influenced by increased light for regulating circadian rhythms.
- **Option 3: Both of the above** - This option is misleading as the primary influence is increased light.
- **Option 4: None of the above** - This is incorrect since the SCN is indeed influenced by light.

5. **Conclusion**: Based on the understanding of how the SCN functions and its relationship with light, the correct answer is **Option 1: Increased light intensity**.

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