Describe how a wave of excitation, which originates in the sinoatrial node (SAN) of the heart, eventually results in ventricular systole.

• SAN send a wave of depolarisation/excitation across the atria causing them to contract• wave cannot pass directly to the ventricle, due to the non-conductive tissue of AV-valves• wave reaches the AVN (in the septum)• passes down bundle of His• up the Purkinje fibres, causing ventricular systole