@inbook{1158760584, author={Kim E. Barrett and Susan M. Barman and Heddwen L. Brooks and Jason X.-J. Yuan}, title={Origin of the Heartbeat & the Electrical Activity of the Heart}, booktitle={Ganong's Review of Medical Physiology, 26e}, publisher={McGraw-Hill Education}, address={New York, NY}, year={2018}, url={accessmedicine.mhmedical.com/content.aspx?aid=1158760584} }