SA node, AV node, bundle of His, bundle branches and Purkinje fibres comprise the nodal tissue of the heart. The nodal musculature has the ability to generate action potentials without any external stimuli, i.e., it is autoexcitable.
Purkinje fibres have fewer myofibrils than most cardiac muscle cells and don’t contract as forcefully. Intercalated disks are well developed between the Purkinje fibres and contain numerous gap junctions. As a result of these structural modifications, action potentials travel along the Purkinje fibres much more rapidly than other cardiac muscle tissue.