Snapshot A 60-year-old man presents to his cardiologist for a follow-up of newly diagnosed diastolic heart failure. He has a history of asthma and chronic obstructive lung disease. He reports that his pulmonologist does not want him to take β-blockers. However, his cardiologist wants to start him on a medication to slow the heart rate. He reassures the patient that this drug acts not on β-receptors but on a Ca2+ channel. (Verapamil) Introduction Ions responsible for the action potential of atria, ventricles, and Purkinje fibers are the same login to view 6 more bullets Ventricular Action Potential Resting membrane potential login to view 2 more bullets Phase 0, upstroke login to view 3 more bullets Phase 1, initial repolarization login to view 4 more bullets Phase 2, plateau login to view 8 more bullets Phase 3, repolarization login to view 6 more bullets Phase 4, resting membrane potential login to view 3 more bullets