The pacesetter in the heart is called

Options

A. Sino-atrial node (SAN)
B. Atrio-ventricular node (AVN)
C. Purkinje fibres
D. Papillary muscle

Answer

To answer the question "The pacesetter in the heart is called," we need to identify the correct term that refers to the structure responsible for initiating the heartbeat.

### Step-by-Step Solution:

1. **Understanding the Heart's Electrical System**: The heart has a specialized electrical conduction system that controls the rhythm of the heartbeat. This system includes several key components: the sinoatrial node (SAN), atrioventricular node (AVN), Purkinje fibers, and papillary muscles.

2. **Identifying the Pacesetter**: Among these components, the sinoatrial node (SAN) is known as the primary pacemaker of the heart. It generates electrical impulses that initiate each heartbeat, setting the pace for the entire heart.

3. **Role of the Atrioventricular Node**: The atrioventricular node (AVN) is also important as it regulates the rhythm by delaying the conduction of impulses from the atria to the ventricles. However, it does not initiate the heartbeat; it only coordinates it.

4. **Understanding Other Components**:
- **Purkinje Fibers**: These fibers are responsible for conducting impulses throughout the ventricular musculature, ensuring the ventricles contract in a coordinated manner.
- **Papillary Muscles**: These muscles are connected to the atrioventricular valves and help in their function but do not play a role in pacing the heart.

5. **Conclusion**: Based on the information, the correct answer to the question is that the pacesetter in the heart is called the **Sinoatrial Node (SAN)**.

### Final Answer:
The pacesetter in the heart is called the **Sinoatrial Node (SAN)**.

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