function dv_dt = simp_cell2(t,v)

global Q
global Ca
global Ve
global Vi
global B
global Rmax
global Kp5
global tp
global frac_on



Ne = v(1);
Ni = v(2);

flow_in = Q.*Ca.*step(t,tp,frac_on);
flow_out = Q.*Ne./Ve;
trans_e_to_i = B.*Ne./Ve;
trans_i_to_e = (Rmax.*Ni./Vi)./(Ni./Vi + Kp5);

dv_dt = zeros(2,1);

dv_dt(1) = flow_in - flow_out + trans_i_to_e - trans_e_to_i;
dv_dt(2) = trans_e_to_i - trans_i_to_e;


function out = step(t,tp,frac_on)

t_cyc = rem(t,tp);

if t_cyc < tp.*frac_on
    out = 1;
else
    out = 0;
end