%rhs for MS model
% for this model W = h

minf = max(0,V);
finf = 0.5*(1.+tanh((V-vh)/kh));
   hinf = 1-finf;
   tauh = topen+(tclose-topen)*finf;
   Fv = gna*W.*max(0,V).^2.*(vna-V) +gk*(vk-V);
   Fw = (hinf-W)./tauh;
