Electrical Activity in Single Myocardial Cells of Limulus polyphemus

Abstract

Single cells of the heart of Limulus were examined in situ with conventional microelectrodes. Resting and action potentials were measured in a total of 20 animals, with 25 penetrations per heart during normal spontaneous activity. Resting-potential values averaged 45 millivolts. Action potentials showed a rapid upstroke and a prolonged plateau. A small, irregular burst of electrical activity occurred during the plateau phase, a discharge presumably associated with the "neurogenic" character of the heartbeat. There was no significant overshoot, nor was there any topographical localization of action-potential "types.".