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P wave of ECG indicates 1. activation ...

P wave of ECG indicates
1. activation of SA node
2. depolarization of atrial muslces
3. spread of excitation from AV node to Purkinje fibres
4. repolarization of atria and depolarization of ventricles

A

1 and 2 are correct

B

2 and 4 are correct

C

1 and 3 are correct

D

1,2 and 3 are correct

Text Solution

AI Generated Solution

The correct Answer is:
To solve the question regarding what the P wave of an ECG indicates, we need to analyze the provided options step by step. ### Step-by-Step Solution: 1. **Understanding the P Wave**: The P wave in an ECG represents the electrical activity associated with the depolarization of the atrial muscles. This is the initial phase of the cardiac cycle where the atria contract to push blood into the ventricles. 2. **Evaluating Option 1**: The first option states "activation of SA node". The SA node (sinoatrial node) is the natural pacemaker of the heart located in the right atrium. When it activates, it generates an electrical impulse that initiates the heartbeat and leads to the depolarization of the atria. Therefore, this option is correct. 3. **Evaluating Option 2**: The second option states "depolarization of atrial muscles". As mentioned earlier, the P wave corresponds to the depolarization of the atrial muscles. This means that when the P wave is present, the atria are contracting. Hence, this option is also correct. 4. **Evaluating Option 3**: The third option states "spread of excitation from AV node to Purkinje fibres". This statement refers to the electrical conduction that occurs after the P wave, specifically during the QRS complex. The P wave does not indicate this process; it indicates the activity before this phase. Therefore, this option is incorrect. 5. **Evaluating Option 4**: The fourth option states "repolarization of atria and depolarization of ventricles". This describes what happens during the QRS complex, not the P wave. The P wave does not indicate the repolarization of the atria or the depolarization of the ventricles. Thus, this option is also incorrect. ### Conclusion: The correct answers are options 1 and 2, which indicate the activation of the SA node and the depolarization of atrial muscles, respectively. Therefore, the P wave of the ECG indicates both the activation of the SA node and the depolarization of the atrial muscles. ### Final Answer: 1. Activation of SA node (Correct) 2. Depolarization of atrial muscles (Correct) 3. Spread of excitation from AV node to Purkinje fibres (Incorrect) 4. Repolarization of atria and depolarization of ventricles (Incorrect)
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