The respiratory centre in the brain is stimulate by

Options

A. `CO_(2) ` concentration in venous blood
B. `O_(2)` concentration in arterial blood
C. `CO_(2)` concentration in arterial blood
D. `O_(2)` concentration in venous blood

Answer

**Step-by-Step Solution:**

1. **Identify the Location of the Respiratory Center:**
- The respiratory center is primarily located in the brain, specifically in the medulla oblongata and the pons.

2. **Understand the Function of the Respiratory Center:**
- The medulla oblongata and pons are responsible for regulating the rate of breathing in the body.

3. **Recognize the Stimuli for the Respiratory Center:**
- The respiratory center is stimulated by chemoreceptors, which are specialized cells that detect changes in the chemical composition of the blood.

4. **Identify the Location of Chemoreceptors:**
- These chemoreceptors are located in the carotid bodies (found in the neck) and aortic bodies (located in the aorta).

5. **Determine What the Chemoreceptors Detect:**
- The chemoreceptors are sensitive to the concentration of carbon dioxide (CO2) in the arterial blood.

6. **Explain the Response to Increased CO2 Levels:**
- When there is an increase in CO2 concentration in the arterial blood, the chemoreceptors send signals to the medulla oblongata, which then stimulates an increase in the rate of breathing.

7. **Conclude with the Answer:**
- Therefore, the respiratory center in the brain is stimulated by the concentration of CO2 in the arterial blood.

**Final Answer:**
The respiratory center in the brain is stimulated by the concentration of carbon dioxide (CO2) in the arterial blood.

---