Results of numerical integration of eqs. (1) and (2). a: Calcium influx α(t). b: Real and approximated indicator-bound calcium concentrations, given the following parameters: pump rate γ(t) = 10 Hz, initial free indicator concentration ymax = 1 μ Mol, indicator backward rate kb = 10 Hz and indicator forward rate kf = 10 Hz/μ Mol. This corresponds to Rb and Rf = 1.0. c: Real and approximated indicator-bound calcium as a function of the free cytosolic calcium. d: Root-mean-square (rms) of the difference between real and approximated signal as a function of the two dimensionless kinetic parameters Rb and Rf. Number on the iso-rms contour lines indicate the rms value as a percent of the real indicator-bound signal.