# CK.ode
# Similar to the Chay-Keizer model.

# For increased G, set kpmca=0.18.

v(0)=-65 
n(0)=0 
c(0)=0.1 

# Auto
par autoc=0, cknot=0.3

# steady state functions 
ninf = 1/(1+exp((vn-v)/sn))
minf = 1/(1+exp((vm-v)/sm))

# set KATP conductance
par gkatp=180

num vk=-75, vca=25
num gk=2700, gca=1000, cm=5300
num vm=-20, sm=12, vn=-16, sn=5, taun=20
par lambda=1.07
par gkca=400
par kd=0.3

# Ikca
Ikca = gkca/(1+(kd/c)^3)*(v-vk)

# Calcium Handling
par kpmca=0.18, f=0.00025
num alpha=4.50e-6

# ICa
Ica = gca*minf*(v-vca)

# Ik
Ik = gk*n*(v-vk)

# Ikatp
Ikatp = gkatp*(v-vk)

# Ca fluxes
Jmem = -(alpha*Ica + kpmca*c)

# equations
dv/dt=-(Ik + Ica + Ikca + Ikatp)/cm
dn/dt=lambda*(ninf-n)/taun
dc/dt = autoc*(cknot-c)+(1-autoc)*f*Jmem

# track some currents
aux tsec=t/1000
aux Condkca=gkca/(1+(kd/c)^3)

@ meth=cvode, atol=1.0e-6, tol=1.0e-6, dt=10, total=150000, maxstor=100000
@ xp=tsec, yp=v, bound=100000000, bell=off
@ xlo=0, xhi=150, ylo=-70, yhi=-10

done