Final answer:
The ability of the depolarizing current to spread through the atrioventricular septum ensures simultaneous contraction of the atria and ventricles, leading to efficient blood pumping.
Step-by-step explanation:
The ability of the depolarizing current to spread through the atrioventricular septum ensures that the atria and ventricles contract simultaneously. The depolarizing current begins in the SA node, spreads through the internodal pathways and atrial myocardial contractile cells, and finally reaches the atrioventricular node. From there, the current travels through the bundle of His, left and right bundle branches, and the interventricular septum, causing the ventricles to contract. The synchronized contraction of the atria and ventricles allows efficient pumping of blood through the heart.