gkatp = 500 if t < than tstim 530 otherwise

ica ik ikca ikatp iir cm

ainf a taua

ninf n taun

rIRinf rIR tauIRr

nIRinf nIR tauIRn

1 1 betaIRn alphaIRn

0.00035 0.07 V 25

0.09 1 0.11 V 100

fraction of open channels

c dact c ip3 dip3 ip3 dinact dinact c

Ca2+ leak is proportional to gradient between Ca2+ and ER

pleak cer c

Ca2+ flux into the ER via SERCA

kserca c

Flux of Ca2+ through the membrane

alpha ica kpmca c

Ca2+ dependent K+ current

gkca w V vk

activation function

1 1 r c sa

activation function

1 1 vn V sn

Ca ionic currents

gca minf V vca

nucleotide-sensitive K+ current

gkatp a V vk

Fraction of K(ca) channels activated by cytosolic Ca2+

c 5 c 5 kd 5

delayed rectifier K+ current

gk n V vk

activation function

1 1 vm V sm

1 alphaIRr betaIRr

1 1 betaIRr alphaIRr

0.15 1 0.05 V 120

30 1 0.04 V 230

1 alphaIRn betaIRn

gir nIR rIR V vir

net Ca2+ efflux from the ER

jleak jip3 jserca

Ca2+ efflux through the IP3R

oinf cer c

cell fcyt jmem jer

fer vcytver jer cell

Increase of maximal conductance of K_ATP channels from 500 to 530 at time=30000 ms

time 3 4

530