Chemosensitive area of respiratory centre in medulla is affected by

Options

A. less `CO_(2)` and `H^(+)` ions
B. less `O_(2)` and `H^(+)` ions
C. excess `CO_(2)` and `H^(+)` ions
D. excess `O_(2)` and `H^(+)` ions

Explanation

### Step-by-Step Solution:

1. **Understanding the Chemosensitive Area**: The chemosensitive area is a part of the respiratory center located in the medulla oblongata of the brain. It plays a crucial role in regulating breathing by responding to changes in the chemical composition of the blood.

2. **Role of CO2 and Hydrogen Ions**: The primary factors that affect the chemosensitive area are the concentrations of carbon dioxide (CO2) and hydrogen ions (H+). When CO2 levels in the blood increase, it leads to an increase in hydrogen ion concentration due to the formation of carbonic acid.

3. **Stimulation of the Chemosensitive Area**: High levels of CO2 and H+ stimulate the chemosensitive area. This stimulation is essential for the respiratory center to respond appropriately to changes in the body's metabolic needs.

4. **Effect on the Respiratory Center**: When the chemosensitive area is stimulated by excess CO2 and H+, it affects the respiratory center, leading to changes in the respiratory processes. Specifically, it can trigger an increase in the rate and depth of breathing.

5. **Activation of Expiration**: The stimulation of the respiratory center primarily influences the process of expiration. During expiration, the body eliminates excess CO2, helping to restore normal levels of carbon dioxide and maintain acid-base balance.

6. **Conclusion**: Therefore, the chemosensitive area of the respiratory center in the medulla is primarily affected by excess CO2 and hydrogen ions (H+).

### Final Answer:
The chemosensitive area of the respiratory center in the medulla is affected by excess CO2 and hydrogen ions (H+).

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