A model of excitation-contraction coupling of mammalian cardiac muscle.

Abstract A model is developed for the excitation-contraction coupling of mammalian cardiac muscle. This model assumes that upon depolarization, the calcium current not only raises the sarcoplasmic Ca 2+ concentration, but also induces the release of Ca from cisternal sarcoplasmic reticulum, whose rate of release depends on the membrane potential. These two main sources of calcium elevate the sarcoplasmic Ca 2+ concentration so that it activates the interaction of myosin and actin and initiates contraction in accordance with Huxley's sliding filament mechanism. The uptake and recycling of Ca 2+ to cisternal sarcoplasmic reticulum is accomplished by the longitudinal sarcoplasmic reticulum. Mitochondria are assumed to accumulate mainly Ca 2+ . The uptake of Ca is considered to be an active process, utilizing energy. The proposed model qualitatively predicts the following electrical-mechanical events often observed in living muscle: tension-voltage-duration, staircase phenomenon, frequency-strength relationship, post-extrasystolic potentiation and contractile behavior after a period of rest.

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