Life starts and ends with a heartbeat. This has been well-known since the times of Aristotle. Ironically, in many cases, we know how and why the heart stops beating, but we know very little about its very first beat, ie, the origin of life itself! Of course, the first heartbeat is generated by ion movements across the sarcolemma of the sinus node cells. But how it happens, which is the first ion to move, and what causes the first action potential is still a mystery. What is extraordinary is that all of these ion movements across the heart membranes occur at the rate of at least 60 times per minute throughout our lifetime—night and day—and generate the heart rate.
