The S.A. node is also called .................. of the heart.

Explanation

**Step-by-Step Text 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 initiating the heartbeat.

2. **Function of the SA Node**: The primary function of the SA node is to generate electrical impulses. These impulses are responsible for triggering the contraction of the heart muscles, leading to the heartbeat.

3. **Common Terminology**: The SA node is often referred to as the "natural pacemaker" of the heart. This is because it sets the rhythm for the heart's contractions and maintains the heart rate.

...