function xdot=Ghhfun(t,x);
% Carol Lucas
% Called function for Morris_Lecar.m
% Note that all parameters are set in the calling program

global VNa VK VL gNa gK gL C Iapp
V=x(1);
m=x(2);
h=x(3);
n=x(4);

taum=1/(0.1*(V+40)/(1-exp(-(V+40)/10))+4*exp(-(V+65)/18));
minf=(0.1*(V+40)/(1-exp(-(V+40)/10)))*taum;
tauh=1/(0.07*exp(-(V+65)/20)+(1/(1+exp(-(V+35)/10))));
hinf=0.07*exp(-(V+65)/20)*tauh;
taun=1/(0.01*(V+55)/(1-exp(-(V+55)/10))+0.125*exp(-(V+65)/80));
ninf=(0.01*(V+55)/(1-exp(-(V+55)/10)))*taun;

xdot(1,1)=(-gNa*m^3*h*(V-VNa)-gK*(V-VK)*n^4-gL*(V-VL)+Iapp)/C;
xdot(2,1)=-(m-minf)/taum;
xdot(3,1)=-(h-hinf)/tauh;
xdot(4,1)=-(n-ninf)/taun;