1. The cardiac electrical system is led by the sinoatrial node which acts as the primary pacemaker at 60 beats per minute. The atrioventricular node and Purkinje fibers can also act as secondary and tertiary pacemakers. 2. There are different types of action potentials in cardiac muscle depending on the region. Sinoatrial and atrioventricular nodes have slow action potentials without phases 1 and 2 due to different ion channel expression compared to ventricular myocytes. 3. Drugs like calcium channel blockers, potassium channel blockers, sodium channel blockers, and beta blockers can be used to pharmacologically manipulate heart rate and conduction velocity by affecting ion channels.