Chemical waves pacemaker

From a distance, the cycles of calcium release and return look like waves of calcium washing through the cell. Heart muscle beats steadily by timing the calcium waves from its sarcoplasmic reticulum in a rhythmic calcium clock pattern. Other cells pick up on the beat set by one calcium clock, coordinating in a pacemaker symphony. Because the calcium ions are charged, this chemical wave is electrical, too, and can be coordinated with an electrical pacemaker. 

M. Stich and A. S. Mikhailov. Complex pacemakers and wave sinks in heterogeneous oscillatory chemical systems. Z. Phys. Chem., 216 521-533, 2002. 

A DC or pulse current polarizes the electrode, and from the electrolytic basic experiment described in Section 2.2 it is also clear that faradaic current flow changes the chemical environment at the electrode surface. Current carrying electrodes are used in such different applications as nerve stimulation, pacemaker catheter stimulation and defibrillation with 50 A passing for some milliseconds. Often a square wave pulse is used as stimulation waveform (e.g., pacemaker), and the necessary overvoltage is of great interest (see Section 9.1). In such applications a clear distinction must be made between tissue nonlinearity (Section 8.4.3) and electrode nonlinearity (this section). Nonlinearity network theory is treated in Section 7.9.3. 

In this last case the coupling between chemical oscillations and hydrodynamics may lead to a complex spatial structuration of the solution inhomogeneous phase locking in the center of the layer and wave generation in the boundary layers. The spatial distribution of the excitable regions and the pacemakers should be related to the symmetry of the underlying convective pattern. Although there exists experimental evidence for the existence of such phenomena (8) more quantitative analysis are needed to explore all the possibilities briefly sketched in the present discussion. 

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