Impulse of heartbeat originates from

Options

A. SA node
B. AV node
C. Vagus nerve
D. Cardiac nerve

Answer

To determine where the impulse of heartbeat originates, we can follow these steps:

### Step 1: Identify the Options
The question provides several options:
1. SA node (sinoatrial node)
2. AD node (atrioventricular node)
3. Vagus nerve
4. Cardiac nerve

### Step 2: Understand the Function of the SA Node
The SA node, or sinoatrial node, is known as the natural pacemaker of the heart. It generates electrical impulses that initiate the heartbeat. The SA node can generate 70 to 75 action potentials per minute, which sets the rhythm for the heart's contractions.

### Step 3: Evaluate Other Options
- **AD Node (Atrioventricular Node)**: This node connects the electrical systems of the atria and ventricles. While it can act as a pacemaker in the absence of the SA node, it does not initiate the heartbeat under normal circumstances.

- **Vagus Nerve**: This is the longest cranial nerve and regulates various bodily functions, including heart rate. However, it does not initiate the heartbeat.

- **Cardiac Nerve**: These are autonomic nerves that supply the heart but do not generate the heartbeat impulse.

### Step 4: Conclusion
Based on the functions of these structures, the impulse of heartbeat originates from the SA node. Therefore, the correct answer is the SA node.

### Final Answer
The impulse of heartbeat originates from the SA node (sinoatrial node).

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