To which substance chemosensitive area is highly sensitive ?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which substance the chemosensitive area is highly sensitive to. This requires knowledge of the chemosensitive area and its function in the respiratory system.

2. **Identifying the Chemosensitive Area**: The chemosensitive area is located near the respiratory center in the medulla oblongata of the brain. This area plays a crucial role in regulating the respiratory rhythm.

3. **Function of the Chemosensitive Area**: The primary function of the chemosensitive area is to detect changes in the levels of certain substances in the blood, specifically carbon dioxide (CO2) and hydrogen ions (H+).

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