04.03 Intrinsic conducting system

The heart can beat of its own accord without a nerve supply, due to the spontaneous electrical activity of specialised cells in the heart – known as the intrinsic conducting system (Figure 4.3). The distribution of impulses allows the heart to contract in a coordinated way. The pacemaker or sinoatrial (SA) node determines the heart rate as it produces electrical impulses at the fastest rate. The electricalimpulses generated by the pacemaker spread to the atria causing them to contract. From the SA node, electrical activity spreads to the atrioventricular (AV) node which distributes the impulses to the AV bundlewhich connects the atria and ventricles. The bundle fibres and Purkinje fibres distribute impulses to the ventricles allowing the ventricles to contract

Figure 4.3 The intrinsic conducting system of the heart (Copyright, QUT)