Which of the following listed respiratory centres in the brain can reduce the expiratory duration upon stimulation?

Options

A. Medullary inspiratory centre
B. Pneumotaxic centre
C. Apneustic centre
D. Chemosensitive centre

Answer

To solve the question regarding which respiratory center in the brain can reduce the expiratory duration upon stimulation, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Respiratory Centers**:
- The brain has several centers that regulate breathing, including the medullary inspiratory center, pneumotaxic center, agnostic center, and chemosensitive center.

2. **Identify the Function of Each Center**:
- **Medullary Inspiratory Center**: Primarily responsible for initiating inspiration; does not specifically reduce expiratory duration.
- **Pneumotaxic Center**: Located in the pons, it plays a crucial role in regulating the rhythm of breathing. It can limit the duration of inspiration, which indirectly affects the duration of expiration.
- **Agnostic Center**: This term is not commonly used in the context of respiratory centers, so it may not be relevant.
- **Chemosensitive Center**: Responds to changes in blood chemistry (like CO2 and O2 levels) but does not directly control the duration of expiration.

3. **Focus on the Pneumotaxic Center**:
- The pneumotaxic center is known as the "switch-off" point for inspiration. When stimulated, it reduces the time spent in the inspiratory phase, thereby increasing the frequency of breathing and consequently reducing the expiratory duration.

4. **Conclusion**:
- Based on the functions of these centers, the pneumotaxic center is the one that can reduce the expiratory duration upon stimulation.

### Final Answer:
The correct answer is **B. Pneumotaxic Center**.

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