How does the conduction system of the heart control the cardiac cycle to ensure enough blood is ejected from the heart?

the sinoatrial node (present in the right atrium) starts the cardiac cycle by producing an action potential which is then transmitted rapidly to the left atrium (causing contraction of both atria) & the ventricles during which are relaxed (diastole) then through the atrioventricular node, the impulses are then transmitted from the atria to the ventricles & then through the bundle of Hiss then left & right bundle branches to all of the ventrricular muscle causing contraction of both ventricles & thus systole

Any defect in the conductive system like ectopic foci (focus producing action potential other than the SA node) or AV block (no impulse transmission from atria to ventricles) leads to defective filling of the heart & pumping of blood