function [upstroke,Time,State] = runbeeler(eNa,eK,gNa,gK)
     
%usage:
%[upstroke,t,s] = runbeeler(50,-85,4,0.35);
%upstroke
%plot(t,s(:,1));


options = odeset('MaxStep', 0.25);
[Time,State]=ode23s('odebeeler',[0,400],[-84,0.5e-7,0,0,1,1,0,1],options,eNa,eK,gNa,gK);
V = State(:,1);
d = diff(V)./diff(Time);  
upstroke = max(d);