PR interval corresponds to ECG changes as

C. i.e. (Atrial - depolarization and conduction through AV node) (551 - Ganong 22nd) (494- Ganong 23rd)ECG IntervalsIntervalNormal Durations (S)Events in the heart during intervalAverageRangePR interval0.180.12-0.20**Atrial depolarization and conduction through AV nodeQRS duration0.08to 0.10Ventricular depolarization and atrial repolarizationQT interval0.40to 0.43Ventricular depolarization plus ventricular repolarizationST interval (QT minus QRS)0.32 Ventricular repolarization* QRS complex denotes - ventricular depolarization*** The normal direction of mean QRS vector is generally said to be - 30 to + 110 on the coordinate system*** U wave - It is due to slow repolarization of papillary muscle* TP segment - It represents polarized state of whole heart* J-point - point between 'S' wave and ST segment. It is a point of "no" electrical activity (305-A.K Jain 3rd)