Explicit Theoretical Analysis of How the Rate of Exocytosis Depends on Local Control by Ca²⁺ Channels

Figure 1

Markov chain models for Ca²⁺ channel (CaV), exocytosis of single granule and granule-CaV complex. (a) Markov chain model for CaV, where C is the closed state, O the open state, and B the inactivated or blocked state. (b) Markov chain model for exocytosis of a single granule adjacent to the plasma membrane, where correspond to the state with no bound Ca²⁺ ions, with one, with two, and with three. (c) Markov chain model for the approximated exocytosis model where the dynamics of states and are described by the auxiliary variable using quasi-steady state approximation for the corresponding ODE model. (d) Markov chain model for the granule-CaV complex where the granule dynamics are described by the model shown in panel (c) and the CaV dynamics by the model shown in panel (a).

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