Which of the following wave in ECG represents depolarisation of the atria ?

Options

A. P - wave
B. Q - wave
C. QRS wave
D. T - wave

Answer

To determine which wave in the ECG represents the depolarization of the atria, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Components of an ECG**: An electrocardiogram (ECG) consists of several waves, including the P wave, QRS complex, and T wave. Each of these waves corresponds to specific electrical activities of the heart.

2. **Identify the P Wave**: The first wave in the ECG is the P wave. It is crucial to recognize that this wave is associated with the electrical activity of the atria.

3. **Function of the P Wave**: The P wave specifically represents the depolarization of the atria. Depolarization is the process by which the heart muscle cells become electrically activated, leading to contraction.

4. **Origin of the P Wave**: The depolarization that leads to the P wave begins at the sinoatrial (SA) node, which is the natural pacemaker of the heart. The electrical impulse spreads throughout the atria from the SA node.

5. **Duration of the P Wave**: The duration of the P wave is typically around 0.08 to 0.10 seconds (or 80 to 100 milliseconds), which indicates how long the atrial depolarization process takes.

6. **Conclusion**: Based on the information above, we can conclude that the P wave in the ECG represents the depolarization of the atria.

### Final Answer:
The wave in the ECG that represents depolarization of the atria is the **P wave**.

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