Figure 7.

Sensitivity of t-system Ca²⁺ accumulation to most influential parameters. (A–H) Each graph shows the variation with one parameter of steady-state Ca_T (A–D) and rate of accumulation of Ca²⁺ in the t-system as quantified by the time taken for Ca_T to reach 50% of its final value (t_½, E–H). Gray points are individual values determined using a Monte Carlo analysis (i.e., 4,000 random combinations of nine parameters). The solid lines are values calculated, using the model, for variation in just the parameter of interest with all other parameter values held constant. The analyses were performed for a Ca_M of 67 nM; the random parameter values were chosen from a range of values spanning ±40% around typical values. A larger span (±60%) was used for RYR leak rate constant. The vertical scatter of the data points reflects the variance from the influences of all the parameters included in the analysis, and the vertical displacement of the solid lines reflects the variance attributable to that parameter. The r² value quantifies the ratio of these two variances.