SA node is the pacemaker, under normal conditions, due to which of the following:-

SA node acts as pacemaker because of slow & spontaneous depolarization (due to slow influx of Na (If) causing || in prepotential). Repolarisation is rapid - due to RAPID EFFLUX OF K+ Automaticity is also provided by AV node but recovery after every impulse is fastest in SA node. Every pa of the hea has its own rhythmicity, but they follows the rhythm of SA-node because it has fastest rate and the main reason is Overdrive suppression .