Figure 10

Role of myofilament Ca^{2 +} sensitivity. Dependence of isometric contraction on myofilament C a^{2 +} sensitivity (MCS). (A) The steady state normalized force versus [C a^{2 +} ] _myo relationship shows a rightward shift with decreasing myofilament C a^{2 +} sensitivity. (B) Traces for normalized force recorded at steady state with an overlay of the [C a^{2 +} ] _myo transient. The inset shows MCS dependent changes in TD₅₀ (time taken from 50% activation to 50% relaxation). (C) Phase plots of normalized force versus the instantaneous C a^{2 +} concentration in the cytosol. (D) Traces for sarcomere length indicating increased shortening with temperature. (E) Degree of sarcomere shortening and peak shortening velocity as a function of MCS. Model generated data corresponds to an idealized rat ventricular myocyte at 22.5°C driven by standard 50 ms voltage pulses at a repetition frequency of 5 Hz.