<em>The P wave</em><em> represents the atrial depolarization (sum of the right and left atriums) and the atrial contraction.</em> In normal circumstances, the P wave is smooth and rounded (<2.5 mm) and no more than 0.12 seconds in duration. It's the first positive deflection (you can see this in the image I added)
<em>QRS complex</em> can include the Q wave, R wave, and S wave, but there are exceptions. <em>It represents the electrical impulse through the ventricles causing the ventricular depolarization.</em> <em>Its amplitude is the largest because ventricles are the chambers with the largest mass in the heart </em>and it has a duration of 0.06-0.10 seconds in adults.
<em>The T wave</em> is the positive deflection that follows the QRS complex, it represents the ventricular repolarization. It is slightly asymmetric (peak closer to its end). Normally this wave follows the QRS complex's direction, if this doesn't happen, it's reflecting a cardiac pathology.
