SA node is called the pacemaker of the heart because

Options

A. it conducts the impulse from AV node
B. it initiates the cardiac impulse
C. it is present in the right atrium
D. it is made up of specialised muscle fibres.

Explanation

**Step-by-Step Solution:**

1. **Understanding the SA Node**: The SA node, or sinoatrial node, is a specialized group of cells located in the right atrium of the heart. It plays a crucial role in the heart's function.

2. **Definition of Myogenic Heart**: The human heart is classified as a myogenic heart, meaning that the cardiac impulses that trigger heartbeats originate from the heart muscle itself rather than from external stimuli.

3. **Function of the SA Node**: The primary function of the SA node is to generate electrical impulses. These impulses initiate the contraction of the heart muscles, leading to the heartbeat.

4. **Role as a Pacemaker**: Because the SA node is responsible for initiating these electrical impulses, it is referred to as the "pacemaker" of the heart. It sets the rhythm and pace of the heartbeat.

5. **Evaluating Other Options**:
- The SA node does not conduct impulses from the AV node; rather, it sends impulses to the AV node.
- While it is located in the right atrium and is made up of specialized muscle fibers, these facts do not explain why it is called the pacemaker.

6. **Conclusion**: The most appropriate reason the SA node is called the pacemaker of the heart is that it initiates the cardiac impulses.

**Final Answer**: The SA node is called the pacemaker of the heart because it initiates the cardiac impulses.

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