What feature distinguishes pacemaker cardiac cells from other cardiac cells? Pacemaker cardiac cells: A. require a stimulus from the vagus nerve in order to reach threshold; other cardiac cells do not. B. reach threshold with much weaker stimuli than other cardiac cells C. have gap junctions, while other cardiac cells do not D. do not require an external stimulus to reach threshold, while other cardiac cells do.
Option D. The pacemaker cardiac cells do not require an external stimulus to reach threshold, while other cardiac cells do.
