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

# Initial conditions.
v(0)=-65 
n(0)=0 
c(0)=0.1 

# Auto
par cknot=0.3, lambda=1.07, gca=1000, autoc=0, kpmca=0.18

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

num gkatp=180, gkca=400
num vk=-75, vca=25
num gk=2700, cm=5300
num vm=-20, sm=12, vn=-16, sn=5, taun=20, kd=0.3

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

# Calcium Handling
num 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

# Time in seconds
aux tsec=t/1000

@ meth=cvode, atol=1.0e-6, tol=1.0e-6, dt=2, total=150000, maxstor=100000
@ xp=tsec, yp=v, bound=100000000
@ xlo=0, xhi=150, ylo=-80, yhi=-10

done