Contractile cells Autorhythmic cells Phase 4 stable potential Phase 4 spontaneous depolarization Phase 0 INa-mediated deporalization Phase 0 Ica-mediated deporalization No pacemaker activity Pacemaker activity Phase 4 resting potential-80mV Phase 4 maximum diastolic potential -65mV Threshold potential -70mV Threshold potential -40mVContractile cells Autorhythmic cells Phase 4 stable potential Phase 4 spontaneous depolarization Phase 0 INa –mediated deporalization Phase 0 ICa –mediated deporalization No pacemaker activity Pacemaker activity Phase 4 resting potential -80mV Phase 4 maximum diastolic potential -65mV Threshold potential -70mV Threshold potential -40mV 26