  Experiments on single ionic channels have contributed to a large extent to
our current view on the function of cell membrane. In these experiments the
main observables are the physical quantities: ionic concentration, membrane
electrostatic potential and ionic fluxes, all of them presenting large
fluctuations. The classical theory of Goldman--Hodking--Katz assumes that an
open channel can be well described by a physical pore where ions follow
statistical physics. Nevertheless real molecular channels are active pores with
open and close dynamical states. By skipping the molecular complexity of real
channels, here we present the internal structure and calibration of two active
pore models. These models present a minimum set of degrees of freedom,
specifically ion positions and gate states, which follow Langevin equations
constructed from an unique potential energy functional and by using standard
rules of statistical physics. Numerical simulations of both models are
implemented and the results show that they have dynamical properties very close
to those observed in experiments of Na and K molecular channels. In particular
a significant effect of the external ion concentration on gating dynamics is
predicted, which is consistent with previous experimental observations. This
approach can be extended to other channel types with more specific
phenomenology.
