We are interested in the system of ion channels present at the membrane of the human red blood cell. The cell, under specific experimental circumstances, presents important variations of its membrane potential coupled to variations of the main ions’ concentration ensuring its homeostasis.

In this collaborative work between biologists and mathematicians a simple mathematical model is designed to explain experimental measurements of membrane potential and ion concentrations. Its construction is presented, as well as illustrative simulations and a calibration of the model on real data measurements. A sensitivity analysis of the model parameters is performed. The impact of blood sample storage on ion permeabilities is discussed.

Contractile force in muscle tissue is produced by myosin molecular motors that bind and pull on specific sites located on surrounding actin filaments. The classical framework to model this active system was set by the landmark works of A.F. Huxley and T.L. Hill. This framework is built on the central assumption that the relevant quantity for the model parametrization is the myosin head reference position. In this paper, we present an alternative formulation that allows to take into account the current position of the myosin head as the main model parameter.

The actin-myosin system is described as a Markov process combining Langevin drift-diffusion and Poisson jumps dynamics. We show that the corresponding system of Stochastic Differential Equation is well-posed and derive its Partial Differential Equation analog in order to obtain the thermodynamic balance laws. We finally show that by applying standard elimination procedures, a modified version of the original Huxley–Hill framework can be obtained as a reduced version of our model. Theoretical results are supported by numerical simulations where the model outputs are compared to benchmark experimental data.