function [t,y]=fzhn
%esto genera una corrida del modelo de Fitzhugh- Nagumo  

%------------- default values --------------
 
global a b c ton toff Ampl;

Ampl=-0.128
a=0.7
b=0.8
c=3.


%------------- time period-------------

tspan = [0; 30];          

%--------------- Pulso ----------------

ton=100
toff=110 

%---------   V - y(1)    W - y(2)   X - y(3)  C - y(4) 


%------------- initial values-------------

%y0=[   8.2540  ;  0.7356 ;   0.2221  ;  0.1563];%middle of a middle spike

y0=[ 1; -0.5];
[t,y] = ode45(@f,tspan,y0);
derivs=[];
size(y,1)
for j=1:(size(y,1))
    derivs=[derivs; f(t(j),y(j,:))'];
end

%----------------ODEs--------------------

%---------------equations (1), (8) but 1/tau, (14), (17)-------------------

function dydt = f(t,y)
     global ton toff a b c Ampl;
     dydt=zeros(2,1);
     dydt(1) =  c*(Ampl + y(2)+y(1)-(1./3.)*y(1)^3);
     dydt(2) = -1.* (y(1)-a+b*y(2))/c ; 
 

%----------------equation (10), but 1/tau-----------------------------

function Itot1 = Itot(xa,ya)
     Itot1= ya+xa-(1/3)*xa.^3  
     
function Iap_t=Iapp(x)
     global ton toff Ampl;
     if x>ton && x<toff
       Iap_t=Ampl;
     else
       Iap_t=0;
     end