The responses of Ca2+ current and concentration to the potential shift via indirect Ca2+ inhibition. The intraciliary Ca2+ concentration (A) and Ca2+ current (B) responses to membrane depolarisation are computed under the assumption of indirect Ca2+ channel inhibition for different concentrations of Ca2+-sensor protein, Cac0. The model predicts that in response to fast membrane depolarisation, the ciliary coupled Ca2+ and membrane potential system generates an intraciliary Ca2+ concentration spike similar to the one observed under the direct Ca2+-inhibition assumptions. The non dimensional membrane potential values following voltage shift from the initial ψ0 = -1.2 are shown in (C) and are the same throughout the figure. The major difference between direct (Figure 3) and indirect mechanisms of inhibition occurs in the steady-state levels of Ca2+ concentration that takes place after the transitional process. The comparison of intraciliary Ca2+ concentration responses for increasing levels of the Ca2+ sensor protein (C, E and G) predicts that intraciliary Ca2+ concentrations following the voltage shift are inversely dependent on the Ca2+ sensor concentration, Cac0. Different concentrations of Ca2+ sensor protein do not affect the membrane depolarisation-induced Ca2+ current (D, F and H).