The excitation of the heart and its modification under the influence of the chemical mediators and the cardiac nerves: I. Some general consequences of the one-factor theory

Abstract

A generalized form of the one-factor theory is applied to the heart. It is found that the effects of acetylcholine and sympathin on the chronaxie can be accounted for only if the decay constant of the excitatory state increases in the presence of acetylcholine, and decreases in the presence of sympathin. With the assumption that this is the only effect of the chemical mediators, it is shown that upon application of acetylcholine to the heart the theory predicts: 1) a rise in the rheobase; 2) an increase in the time required for excitation by constant currents; 3) no change in the threshold with condensor discharges of brief duration; 4) a decrease in the spontaneous heart rate; 5) a sudden and complete inhibition of the spontaneous heart rate with excessive concentrations of acetylcholine. In general, the effects of sympathin predicted by the theory oppose those of acetylcholine.