%% ODE for reduced open-cell Keizer-Levine model
%% Carol Lucas

function xdot=klopenfun_red(t,x,flag,jimax,jistart,jiend,kcm)
%ode45('klopenfun_red',[0:500],[.2;2.6],[],1.5,50,400,.1) for Figure 5.8;
C=x(1,1);
CT=x(2,1);
jin=and(t>=jistart,t<=jiend)*jimax;
fi=0.01;sigma=.02;
ka=0.4;kb=0.6;kcp=1;kc=kcm/kcp;
    
vPMCA=5; KPMCA=.6;vRYR=5;vleak=.2;vSERCA=100;KSERCA=.2;

winf=(1+(ka/C)^4+(C/kb)^3)/(1+(1/kc)+(ka/C)^4+(C/kb)^3);
Cer=(CT-C)/sigma;
P=winf*(1+(C/kb)^3)/(1+(ka/C)^4 + (C/kb)^3);
jRyR=vRYR*P*(Cer-C);
jPMCA=vPMCA*C^2/(KPMCA^2+C^2);
jSERCA=vSERCA*C^2/(KSERCA^2+C^2);
jleak=vleak*(Cer-C);

xdot(1,1)=fi*(jRyR+jleak-jSERCA+jin-jPMCA);
xdot(2,1)=fi*(jin-jPMCA);