Heart of heart is-

Options

A. SA-node
B. AV-node
C. Bundle of His
D. Purkinje fibres

Answer

To answer the question "Heart of heart is-", we need to identify the part of the heart that plays a crucial role in regulating its rhythm and function.

### Step-by-Step Solution:

1. **Understanding the Structure of the Heart**: The human heart is primarily made up of cardiac muscle tissue and has a complex structure that includes various chambers and valves.

2. **Identifying the Pacemaker**: Within the heart, there is a specific area known as the sinoatrial (SA) node, which is located in the right atrium. This node is often referred to as the "pacemaker" of the heart because it initiates the electrical impulses that trigger heartbeats.

3. **Function of the Pacemaker**: The SA node generates electrical impulses at a rate of approximately 72 beats per minute under normal resting conditions. These impulses cause the heart muscles to contract and pump blood.

4. **Role of the Atrioventricular (AV) Node**: After the SA node, the electrical impulse travels to the atrioventricular (AV) node, which serves as another important component in the conduction system of the heart. The AV node helps to coordinate the timing of the heart's contractions.

5. **Conduction Pathway**: The electrical impulses then travel through specialized fibers known as Purkinje fibers, which distribute the impulses throughout the ventricles, leading to their contraction and the pumping of blood to the lungs and the rest of the body.

### Final Answer:
The "heart of heart" refers to the **sinoatrial (SA) node**, which acts as the pacemaker of the heart.

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