THE NONLINEAR DYNAMICS OF RHYTHMS TRANSITION IN SINGLE CARDIAC CELL

The Morris-Lecar(ML) model was used to investigate the mechanisms of the experimentally discovered rhythms transition in cultured single cardiac cells.Stimulated by the extern current(Iext),the deterministic ML model showed a transition process from the resting state of polarization to the resting state of over-depolarization through the uninterrupted regular rhythm.However,the delayed after-depolarization(DAD) rhythm and the early after-depolarization(EAD) rhythm similar to that found in experiment were appeared in the model containing stochastic fluctuation. The DAD rhythm located near Hopf bifurcation point between the resting state of polarization and the uninterrupted regular rhythm, and the EAD rhythm located near Hopf bifurcation point between the uninterrupted regular rhythm and the resting state of over-depolarization. Those results indicated that the DAD and EAD rhythm were generated by disturbing activation of small stochastic fluctuation.