Genetically engineered light sensitive cardiac cell stimulated conventionally with an electric field, dashed lines, and optically with light, solid lines. Temporal evolution of fast sodium current INa, background sodium current IbNa, sodium potassium pump current INaK, sodium calcium exchanger current INaCa, inward rectifier current IK1, rapid delayed rectifier current IKr, slow delayed rectifier current IKs, plateau potassium current IpK, transient outward current It0, L-type calcium current ICaL, background calcium current IbCa, plateau calcium current IpCa, leakage current Ileak, sarcoplastic reticulum uptake current Iup, sarcoplastic reticulum release current Irel, and channelrhodopsin current IChR2. The current dynamics for the electrically stimulated cell have been delayed by 34 ms for the purposes of comparison against the optically stimulated cell.