'P' wave of ECG occurs before the:

• onset of ventricular ejection

• end of atrial contraction

• begining of atrial contraction

• none of the above

C.

begining of atrial contraction

Electrocardiography (ECG or EKG) is the process of recording the electrical activity of the heart over a period of time using electrodes placed over the skin.

Each peak in the ECG is identified with a letter from P to T that corresponds to a specific electrical activity of the heart.

P- wave represents the electrical excitation or depolarisation of the atria. It is the first upward deflection caused by the passage of the action current over the auricles. Its average duration is about 0.1 sec.

QRS complex represents depolarisation of ventricles.

T- wave represents return of the ventricles from excited to normal state.