Figure 4

Unloaded contraction. Twitch response - Unloaded contraction. (A) The total muscle force is plotted corresponding to C a^{2 +} transients with peak values 1.1 (∗), 0.9, 0.8, 0.7, 0.6, 0.5 (∙) μ M as in Figure 3B. (B) Cell shortening twitches as a function of C a^{2 +} activation. The cell is allowed to contract from its equilibrium length of 1.9 μ m against the passive elastic and viscous restoring forces in the model of Rice et al. ([13]; Figure 1). Increasing peak translating into increased amount of activator C a^{2 +} causes a decrease in time to peak shortening. The inset shows self-normalized sarcomere length for peak values of 1.1 (∗) and 0.5 (∙) μ M. Model generated data corresponds to an idealized rat ventricular myocyte at 22.5°C.