<prompt> All are true about cardiac muscle EXCEPT?Phase 1 of depolarization is due to opening of voltage gated sodium channelsPhase 2 of depolarization is due to slow opening of voltage gated calcium channelsPhase 3 of repolarization is due to K effluxTetany of cardiac muscle is never seen  <response>: Ans. A Phase 1 of depolarization is due to opening of voltage gated sodium channelsPhase 0 Rapid depolarization due to opening of voltage sensitive sodium channelsPhase 1 Rapid repolarization due to closure of sodium channels and opening of one type of K channelsPhase 2 Plateau phase due to slow and prolonged opening of voltage gated calcium channelsPhase 3 Final repolarization to RMP is due to closure of Ca and 4 channels and a slow delayed increase of K effluxSince cardiac muscle remains in refractory period until phase 4, tetanic contractions which can occur in skeletal muscle cannot occur in cardiac muscle. 