# v-s pseudo-phase plane to make Z-curves and s nullclines (Figs. 5, 7)
init v=-60, s=0.4
# Conductances in pS; currents in fA; Ca concentrations in uM; time in ms

par lambda=1.0, iapp=0, c=0.1, cer=10
# Ik
par gk=2700.0, vn=-16, sn=5.6, vk=-75, 
par taun=20
# Is
par gs=200, vs=-52, ss=5, taus=20000, r=0
# Ikatp
par gkatp=120.0
# Ica
par gca=1000, vca=25, vm=-20, sm=12
# Ikca
par gkca=0.0, kd=0.6, nh=5
# Icrac
par vcrac=-30.0, cerbar=4.0, gcracbar=0.0, sloper=1
# Miscellaneous
par cm=5300
# Calcium Handling
par alpha=4.50e-6, kc=0.2, f=0.01

# Functions

ninf(v) = 1/(1+exp((vn-v)/sn))
minf(v) = 1/(1+exp((vm-v)/sm))
sinf(v) = 1/(1+exp((vs-v)/ss))
ica(v) = gca*minf(v)*(v-vca)
ikca(v,c) = gkca/(1+(kd/c)^nh)*(v-vk)
ikatp(v) = gkatp*(v-vk)
icrac(v) = gcrac*(v-vcrac)
ik(v,n) = gk*n*(v-vk)
is(v,s) = gs*s*(v-vk)

# Expressions

gcrac = gcracbar/(1.0+exp((cer-cerbar)/sloper))
jmem = f*(-alpha*ica(v) - kc*c)

# Equations

v' = (-ica(v) - ik(v,ninf(v)) - is(v,s) - ikatp(v)  - ikca(v, c) - icrac(v) + iapp)/cm
s' =  (sinf(v) + r - s)/taus

@ meth=gear, dt=20.0, total=40000, maxstor=10000
@ xp=s, yp=v
@ xlo=-0.25, xhi=1.0, ylo=-75, yhi=-10

done