Model of Boltzmann gated channel conductance vs. transmembrane voltage for any ion. Conductance change has fixed timelag, tau.

Description

 Provides current voltage relationships for potassium currents
 through a passive leak conductance and through a voltage-gated channel 
 in a membrane. Gives Nernst potentials. Allows changing of gate charges
 and mean Em for the gate, EKchan, as well as concentrations and temperature 
 in order to explore the Boltzmann relationships.

 Model is essentially that of Vboltzmann but to demosntrate a time lag in the 
 conformational change and the conductance, the transmembrame voltage Em is 
 changed to be a function ot time, so the independent variable is "t". The 
 lag is not in the Hille description on p19, but later in the book.
 
 Model for monovalent cation in water driven by electrochem gradient
 Membrane separates 2 regions of fixed concentrations, Ko and Ki
 Solute activities are unity. Currents do not reach S.S. instantaneously
 but are delayed by a single exponential lag.
 Single channel conductance about 300 pSiemens; 10^6 chan -> 300 uS.
 See Notes, section J, within this .proj file for a suggestion to create a tau(t, Em).

Figure: Membrane current (Jelect) and conductance (gK) as a function of transmembrane potential. Current flows through passive leakage and a voltage-gated channel. Dashed lines (Jelecttau and gKlag) show the effect of conductance time lag (Current does not reach S.S. immediately).

Equations

The equations for this model may be viewed by running the JSim model applet and clicking on the Source tab at the bottom left of JSim's Run Time graphical user interface. The equations are written in JSim's Mathematical Modeling Language (MML). See the Introduction to MML and the MML Reference Manual. Additional documentation for MML can be found by using the search option at the Physiome home page.