Theoretical analysis of the sinus node pacemaker responses modes depending on temporal characteristics of acetylcholine effect upon them

We have simulated electrical and vagal stimulation of a central sino-atrial node cell. Both positive and negative chronotropic effects have been observed. The type of the effect is dependent on the phase of stimulation. Stimulation in early phases resulted in shortening of the cycle, while stimulation in late phases resulted in prolongation of the cycle.