Cardiac action potentials of various cell types-a model study

Action potentials of epicardial cells, M-cells, endocardial cells and Purkinje fibers were simulated in a computer model with account being taken of neural influencing factors and drugs. The transport mechanisms of sodium, potassium, calcium and chlorine ions through the cell membrane are described mathematically, as is the exchange of calcium between the myoplasm and the sarcoplasmic reticulum. Ionic currents of altogether 17 channels and pumps of the cell membrane and the sarcoplasmic reticulum are provided by the model. The presented study concentrates on the transient outward potassium current I_K,to , which contributes to the formation of a notch during the early repolarisation phase of the action potential. As an aftereffect of this current, the M-cell action potential shows a deflection in the late repolarisation phase. Furthermore, the effects of sympathetic drive and various drugs were demonstrated in the model as well as the shortening of the action potential duration with increasing stimulation frequency