by Rebecca A. Capel and Derek A. Terrar*
*British Heart Foundation Centre of Research Excellence,
Department of Pharmacology, University of Oxford, Oxford, UK

It reviews the roles of calcium in pacemaker activity of the sino-atrial node (SAN).

It discusses the ongoing debate between the “membrane clock” and “calcium clock” theories, emphasizing the diverse and crucial roles of calcium beyond just spark-like events. The paper explores various calcium-dependent mechanisms, their influence on ion channels and enzymes, and their contributions to pacemaker activity under different conditions, ultimately broadening the understanding of calcium’s role in heart rhythm regulation.