Conducting cells of the heart follow a sequence of depolarizationThe rapid influx of positive ions (sodium and/or calcium) into a cell – depolarization is necessary for contraction to occur. A depolarizing wave moves through the myocardium on average along a trajectory or vector. A vector is a force moving... followed by a period that they cannot depolarize (absolute refractory periodPeriod when the cardiac cells cannot depolarize irrespective of the strength of the electrical impulse. 1. Six Second ECG Guidebook (2012), T Barill, p. 189). This is then followed by a readiness period when they can depolarize again (and help continue the electrical wave across neighbouring cells). Occasionally, a wave front initiated by a sinus or a junctional site arrives earlier than neighbouring cells are ready. This stops the wave front. Early atrial activity results in a unique P waveA wave generated from the depolarization of the atria; the P wave is upright when originating from the SA node. The P wave represents the depolarization of the right and left atria. The P wave begins with the first deviation..., and occasionally that’s all – the impulse fails to conduct across the junctionConnects the atria to the ventricle and slows the impulse conduction speed sufficiently to allow for atrial kick; the junction consists of the AV node and the bundle of His; the junction is a supraventricular structure. 1. Six Second ECG... or across 1 or 2 bundle branchesThe bundle of His terminates in the right and left bundle branches, insulated rapidly conducting electrical pathways that connect with the Purkinje network and thus begin depolarizing waves across the ventricles; the left bundle branch splits into three smaller branches....
