Phase 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...: for myocardial cells the slow sodium channels open, and then, if threshold potentialThe electrical potential point across the cell membrane where the cell’s channels open to cause depolarization; for example, in the heart’s myocardial cells, the fast sodium channels open if the electrical potential across the cell’s membrane is –60 to –70... is reached, fast sodium channels open; note that cells of the SA & AV nodeIs located in the inferior aspect of the right atria; functions to slow the conduction speed to allow for atrial conduction prior to ventricular conduction (atrial kick); also serves as a pacemaker if the SA node fails to fire. The... are calcium dependent for depolarization.
1. Six Second ECG GuidebookA Practice Guide to Basic and 12 Lead ECG Interpretation, written by Tracy Barill, 2012 Introduction The ability to correctly interpret an electrocardiogram (ECG), be it a simple six second strip or a 12 lead ECG, is a vital skill... (2012), T Barill, p. 202