Conduction pathways in the heart

Conduction Mechanism of the Heart

The chambers contract and relax in a regular sequence and this action is controlled by an electrical impulse. This impulse begins in the heart’s pacemaker (the sino-atrial node), which is situated in the right atrium of the heart. The impulse is conducted through the right and left atria to the atrioventricular node, which is just above the ventricles, in the wall between the two atria. It then proceeds after a very slight delay, down through the Bundle of His between the right and left ventricles. This bundle of fibres divides into the left bundle for the left ventricle and the right bundle for the right ventricle. The impulse spreads down the bundles and activates the ventricular muscle from the bottom up, causing contraction of the ventricles.

Therefore the electrical current travels down regulated pathways at a specific speed.

If there is a disorder of the system at any specific point (i.e. where the impulse originates) or any problem with the path of conduction or if the pathway itself is abnormal or extra to the usual pathway or if the rate is abnormally fast or slow, an arrhythmia is said to occur.