In ECG, P-R interval corresponds to

Options

A. time delay in A-V node
B. S-A nodal conduction time
C. increased ventricular contraction
D. time interval between onset of ventricular contraction

Explanation

To answer the question regarding what the P-R interval corresponds to in an ECG (electrocardiogram), we can break down the explanation step by step:

### Step-by-Step Solution:

1. **Understanding the ECG Components**: The ECG consists of several waves and intervals, including the P wave, QRS complex, and T wave. Each of these components represents different electrical activities of the heart.

2. **Identifying the P Wave**: The P wave corresponds to the depolarization (contraction) of the atria, which are the upper chambers of the heart. This is when the atria contract to push blood into the ventricles.

3. **Identifying the R Wave**: The R wave is part of the QRS complex and represents the depolarization (contraction) of the ventricles, which are the lower chambers of the heart. This occurs after the atria have contracted.

4. **Understanding the P-R Interval**: The P-R interval is defined as the time from the beginning of the P wave to the beginning of the R wave. This interval reflects the time taken for the electrical impulse to travel from the atria through the atrioventricular (AV) node to the ventricles.

5. **Function of the AV Node**: The AV node acts as a gatekeeper, delaying the electrical signal before it passes to the ventricles. This delay allows the atria to fully contract and fill the ventricles with blood before the ventricles contract.

6. **Conclusion**: Therefore, the P-R interval corresponds to the time delay at the AV node, which is crucial for proper timing of the heart's contractions.

### Final Answer:
The P-R interval in an ECG corresponds to the time delay in the atrioventricular (AV) node.

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