Figure 7. Predicted bright flash responses. Bright flash responses are predicted under five sets of conditions, indicated by the different colors. Black traces: No shut-off of either R* or G*/PDE*. The dashed black trace plots the Gaussian analytical expression of Lamb and Pugh [1]; the continuous black trace plots the solution of the differential equations (with k_R* = 0 and k_E = 0). Green traces: With normal shut-off of G*/PDE* but no shut-off of R*, achieved by setting k_R* = 0 but leaving k_E as in Table 2. Red traces: Three-state model of R* shut-off, with parameters as in the Tables and Figure 4. Here, the mean R* time course was calculated by numerical integration of the differential equations representing the reactions in Figure 1E. Blue traces: Exponential decay of mean R* activity, with a time constant k_R*⁻¹ = 40 ms. At higher intensities, some traces are obscured by overlying traces, which were plotted in the sequence black, green, red, blue. For all traces except the Gaussian analytical model, the downstream reactions were integrated using the lumped model versions of Equations (4.1) – (4.9), with the default parameters in Table 2 (except where k_E was set to zero). In all cases, the gain factor ν_RE β_sub was set to 7.2 s⁻² (giving an amplification constant of A = 21.6 s⁻²), the flash duration was zero, and the flash intensities were 10, 30, 100, 300, 1000, 3000, and 10,000 photoisomerizations.