The memory effect and phase response of model sinoatrial node cells

Phase resetting of cells in response to a brief current pulse has been observed in a variety of nervous tissues including cardiac cells. External stimulation of the sinoatrial node is due to largely positive currents, depolarising the cells, except for some ACh interactions. Factors influencing this include the timing of the current injection, its polarity, magnitude and duration. Both prolongation and shortening of the interbeat interval can occur. The effect of current injection on cells of the sinoatrial node have been analysed using a model cell developed by [Dokos, S., B. Celler, N. Lovell, Theor. Biol. vol. 181(3): 245-72, 1996]. This model defines the ionic currents that cause the spontaneous electrical activity of the cells.