Which of the following can alter respiratory mechanism?

Options

A. Pneumotaxic centre
B. Chemosensitive centre
C. Respiratory rhythm centre
D. Both (1) & (2)

Answer

To answer the question "Which of the following can alter respiratory mechanism?" we need to analyze the options provided: pneumotaxic center, chemosensitive center, respiratory rhythm center, and both one and two.

### 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 send inhibitory impulses during inspiration, which helps prevent over-distension of the lungs.
- It plays a crucial role in maintaining a balance between inspiration and expiration by regulating the respiratory rhythm.

**Hint**: Remember that the pneumotaxic center helps control the timing of breaths.

2. **Understanding the Chemosensitive Center**:
- The chemosensitive center is located adjacent to the respiratory rhythm center.
- It is highly sensitive to the levels of carbon dioxide (CO2) and hydrogen ions in the blood.
- When there is an increase in CO2 and hydrogen ions, the chemosensitive center activates and signals the respiratory rhythm center to adjust the breathing rate accordingly.

**Hint**: Focus on how changes in blood chemistry can influence breathing patterns.

3. **Understanding the Respiratory Rhythm Center**:
- The respiratory rhythm center consists of groups of neurons located in the medulla and pons.
- It is responsible for generating and maintaining the rhythm of respiration.
- While it is the center that ultimately controls respiration, it is influenced by both the pneumotaxic center and the chemosensitive center.

**Hint**: The rhythm center is the "control center" for breathing, but it relies on inputs from other centers.

4. **Conclusion**:
- Both the pneumotaxic center and the chemosensitive center play significant roles in regulating the respiratory rhythm center.
- Therefore, they both can alter the respiratory mechanism.
- The correct answer to the question is "both one and two".

**Final Answer**: The correct option is "both one and two".