1) SAN produces a wave of electrical excitation that spreads across atria and cause them to contract
2) Wave is prevented from spreading to the ventricles by the atrioventricular septum
3) Wave enters the AVN
4) There is a short delay. Then, the AVN sends a wave of excitation along a series of Purkyne fibres (form bundles of His)
5) The wave travels through the atrioventricular septum (to the base of ventricles) down the bundle of His and branch into the smaller Purkyne fibres.
6) Wave released from these fibres causes ventricles to contract in unison from bottom upwards
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