n = W;
     
AM=.1*(25.-V)./(exp(2.5 -0.1*V)-1.);
BM=4.*exp(-V/18.);
AN=.0001*(10.-V)./(exp(1.-0.1*V)-1.);
BN=.125*exp(-V/80.);

h = rn0 - n;
aminf = AM/(AM+BM);
aminf = aminf.^3;
Ina = gnabar*aminf.*h.*(V-Vna) ;
Ik = gkbar*n.^4*(V-Vk);
Icl = .3*(V-Vl);
      
Fv = -Ina-Ik-Icl;
Fw=AN*(1.-n)-BN*n;
