Figure 9.

A theoretical model of the repetitive [Ca²⁺]_cy spikes in E. viridis. A, Schematic model of the Ca²⁺ fluxes involved in generating repetitive [Ca²⁺]_cy spikes in E. viridis. The [Ca²⁺]_cy, y, and Sr²⁺ activity, Sr, cause a Ca²⁺/Sr²⁺-induced Ca²⁺ release (β) from an internal Ca²⁺ store. The Ca²⁺ store is refilled by a Ca²⁺-ATPase (c), and there is a continuous Ca²⁺ efflux due to a “leak” (α). A plasma membrane Ca²⁺-ATPase removes Ca²⁺ from the cytoplasm (b), and there is a Ca²⁺ influx from the external medium (A). B, Temporal response of the system depicted in A and described by Equation 2. The [Ca²⁺]_cy, y, is plotted as a function of time, t, for: A = 0.2; b = 1; c = 2; α = 0.05; β = 15.7; K = 1; Sr = 0.1; n = 4; x(t=0) = 2.8; y(t=0) = 0.2. For the sake of simplicity no units are given and the axes are given in arbitrary units.