Question

P wave in ECG represents which of the following actions in the heart?

• A. Repolarisation of the atria
• B. Depolarisation of the atria
• C. Depolarisation of the ventricles
• D. None of the above

Answer 1

The correct option is B Depolarisation of the atria

Electrocardiograph is a machine that produces electrocardiogram. ECG is a graphical representation of the electrical activity of the heart during a cardiac cycle. The ECG produces peaks and each peak is marked with a letter from P to T that corresponds to a specific electrical activity of the heart.

P wave in the ECG represents the electrical excitation of the atria (depolarisation) which causes contraction of both the atria. The QRS wave represents the depolarisation of the ventricles, which causes the ventricular contraction. Contraction starts shortly after the Q wave and marks the beginning of systole (a period of contraction of the ventricles). The T wave represents the return of ventricles from excited to normal state (repolarisation). The end of the T wave marks the end of the systole. The number of QRS wave complexes that occur in a given time period can be used to calculate the number of heart beats per minute.