Purkyne fibres

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Purkyne fibres (Purkinje fibres) Modified fibres in the mammalian heart that originate in the bundle of His and spread out in a network over the ventricles. Action potentials generated in the sinoatrial node (the pacemaker of the heart) are conducted extremely rapidly through the ventricles, due to the extensive branching of the Purkyne fibres, causing both ventricles to contract almost simultaneously.