Figure 6.

Proposed mechanism for excitation–contraction coupling. In the resting state (a), a slow inward flux of Ca²⁺ to the SR involves both the DHPR (labelled L in the figure) and an RyR (labelled R in the figure). There is also a slow exit of Ca²⁺ from the SR to the cytosol (since the Ca²⁺ channel is inactivated during the resting state (56)) this is indicated by the thin dashed lines. In the excited state (b), movement of the DHPR exposes the Ca²⁺ release site of the RyR, Ca²⁺ rapidly flows from the SR to the cytosol. (A color version of this figure is available in the online journal.)