Which of the following is not possible when pneumotaxic center is sending a strong signal ?

Options

A. Rate of breathing increases
B. Complete filling of lungs
C. Decreased duration of inspiration
D. Decreased duration of expiration

Answer

### Step-by-Step Solution:

1. **Understanding the Pneumotaxic Center**:
- The pneumotaxic center is located in the upper part of the pons in the brain. Its primary function is to regulate the rate and duration of breathing, particularly the inspiratory phase.

2. **Function of the Pneumotaxic Center**:
- When the pneumotaxic center sends signals, it can either increase or decrease the duration of inspiration. A strong signal from this center typically results in a shorter inspiratory phase.

3. **Effects of a Strong Signal**:
- A strong signal from the pneumotaxic center reduces the duration of inspiration to about 0.5 seconds.
- It also increases the respiratory rate significantly, potentially up to 30 to 40 breaths per minute.

4. **Analyzing the Options**:
- Given the effects of a strong signal, we need to determine which option is not possible:
- **Option 1**: Increase in respiratory rate – This is possible.
- **Option 2**: Complete filling of lungs – This is not possible due to the reduced duration of inspiration.
- **Option 3**: Decrease in duration of inspiration – This is possible.
- **Option 4**: Decrease in duration of expiration – This is also possible.

5. **Conclusion**:
- The option that is not possible when the pneumotaxic center is sending a strong signal is **Option 2: Complete filling of lungs**. This is because the short duration of inspiration does not allow for complete lung filling.