ANATOMY

Detailed explanation-1: -The P wave represents the electrical depolarization of the atria. In a healthy person, this originates at the sinoatrial node (SA node) and disperses into both left and right atria.

Detailed explanation-2: -The P wave represents the depolarization of the left and right atrium and also corresponds to atrial contraction. Strictly speaking, the atria contract a split second after the P wave begins. Because it is so small, atrial repolarization is usually not visible on ECG.

Detailed explanation-3: -The P wave of the ECG represents atrial depolarization, which is followed by contraction and an increase in pressure in the atria (atrial systole). The AV valves are open, and there is no valve between the atria and veins, so this small increase in pressure is also evident in the ventricle (a wave) and in the veins.

Detailed explanation-4: -The electrical excitation of atria is called depolarization of atria and it causes contraction of atria. In an ECG, the first downward deflection is called Q-wave. It occurs just after the P-wave.

Detailed explanation-5: -The atrial rate is indicated by the P waves. There are almost exactly five large boxes between P waves, indicating an atrial rate of 60 bpm. There are a total of ten P waves on this strip (difficult to see some of them, as they are intermittently buried in the QRS complexes) and 10 x 6 = 60.