Standard Hodgkin-Huxley ion channel

CONICAL object class#include ChanStd.h
Base Classes
ChanABAlpha/Beta Hodgkin-Huxley Channel
Derived Classes
Member Functions & Variables
virtual real BetaH ( const real V );
virtual real AlphaH ( const real V );
virtual real BetaM ( const real V );
virtual real AlphaM ( const real V );
virtual void SetFunc ( StdEqnType pType , StdForm pForm , real pA , real pB , real pV0 );
ChanStd ( VSink * pTo , VSource * pComp , real pMaxG = 0 . 1 , real pMexp = 1 , real pHexp = 1 );
ChanStd ( Compartment * pTo , real pMaxG = 0 . 1 , real pMexp = 1 , real pHexp = 1 );

Objects of the ChanStd class are active channels whose gating variables (M and H) are updated by one of three standard equation forms. All three formulas use the same parameters (A, B, and V0) but these have very different meanings from form to form. The equations used are defined in StdForms.h, and explained below.

With this class, you can create almost any voltage-gated ion channel in the literature by choosing an appropriate equation form and parameters.

ExpForm: f(v) = A * exp((v-V0)/B)

The Exponential equation form generates a curve which accelerates very sharply on one end, and approaches zero on the other. A and V0 are related, such that f(V0) = A. Changing A scales the entire curve, while changing V0 shifts it on the voltage axis. B defines the "slope" of the curve, loosely speaking. Typical values are A=4000, B=-0.018, and V0=-0.070.

LinForm: f(v) = A when v=V0, A * (v-V0) / (exp((v-V0)/B) - 1) otherwise

This equation produces a curve that is approaches zero asymptotically on one end, and approaches a straight line on the other. The meaning of A and B is similar to in ExpForm, but negative; f(V0) = -A, and B is (roughly) the negative of the slope. Typical values are A=-100000, B=-0.10, and V0=-0.045.

SigForm: f(v) = A / (exp((v-V0)/B) + 1)

This equation produces an S-shaped curve, which approaches zero on one end and approaches A at the other. A is the maximum approached by f(v), and V0 is the voltage at which half this value is reached (i.e. f(V0) = A/2). B is the inverted, negative slope of the curve; negative values produce a positive slope, and larger absolute values produce a shallower, more gradual curve. Typical values are A=1000, B=-0.010, and V0=-0.040.