Heart beat is controlled by which cranical nerve `:-`

Options

A. `X^(th)`
B. `IX^(th)`
C. `III^(rd)`
D. `V^(th)`

Answer

### Step-by-Step Solution:

1. **Identify the Question**: The question asks which cranial nerve controls the heartbeat.

2. **Recall Cranial Nerves**: There are 12 pairs of cranial nerves in the human body. Each has specific functions and areas of control.

3. **Identify the Relevant Cranial Nerve**: The cranial nerve that is primarily responsible for controlling the heart rate is the 10th cranial nerve.

4. **Name the 10th Cranial Nerve**: The 10th cranial nerve is known as the **vagus nerve**.

5. **Understand the Function of the Vagus Nerve**: The vagus nerve is involved in various functions, including:
- Regulation of heart rate
- Control of muscles in the larynx
- Influence on the lungs, stomach, and intestines

6. **Origin of the Vagus Nerve**: The vagus nerve originates from the **medulla oblongata** in the brain.

7. **Distribution of the Vagus Nerve**: The vagus nerve has a wide distribution, affecting the heart, lungs, stomach, and intestines.

8. **Conclusion**: Therefore, the cranial nerve that controls the heartbeat is the **10th cranial nerve, also known as the vagus nerve**.