A model of calcium distribution in the sarcomere during activation of contraction was developed. It allows for diffusion and binding of calcium ions to various sarcoplasmic binding sites in the three dimensional spatial coordinate system. The model was used to analyze the influence of kinetic characteristic of binding processes on the temporal and spatial distribution of calcium in the sarcomere during activation of contraction by the action potential and by rectangular depolarizing pulses. The hypothesis concerning the calcium release control in the membrane of terminal cisternae was tested.