We present here a major update of our smooth muscle model. It's aim is to enable the simulation of smooth muscle contraction under functional electrical stimulation (FES). The main addition is a model of calcium dynamics in the smooth muscle cell. It links the calcium concentration to the electrical potential of the membrane cell, therefore to the neural stimulation. This concentration is used to command the microscopic mechanics of the muscle, leading to contraction. We also refined the mechanical model. As smooth muscle have way slower dynamics than striated ones, it is possible to neglected the second order terms. We choose to simulate a well known example : the behavior of the bladder under the stimulation of a Finetech / Brindley implant. This way we can compare our qualitative results with the experimental data available in the literature. They show good consistency both in shape and time course. To obtain quantitative simulations, we need to perform the identification of the model through in-vivo testing on animals. Once this validation step done, it will be possible to apply our methodology to human bladder.