ABSTRACT
In this chapter we will introduce several examples of systems that span an entire spectrum of length scales, ranging from waves of calcium concentration seen at the intracellular scale, all the way to large-scale patterns of plankton growth in oceans that can span hundreds of kilometers. Our examples are spread across a wide range of scientific disciplines, including the physical (patterns in surface reactions), chemical (Belousov-Zhabotinsky reaction), physiological (uterine contractions, spreading depressions in the brain), biochemical (intracellular calcium waves), biological (cAMP waves in Dictyostelium colonies), ecological (phytoplankton growth), and pathological (spatial spread of infectious diseases) systems. The common feature linking these diverse systems is that their dynamics can be modeled using excitable media models, with many of them displaying spatial patterns like spiral waves and scroll waves. We will briefly discuss each of these examples with the aim of giving a flavor of the diversity observed in naturally occurring excitable systems.
