TABLE 1.

Model parameter values; further details of the selection of the parameter values can be found in the text

Symbol	Definition	Value	Notes
Receptor regulation
kr	Receptor recycling rate	0.0023 s−1	Fit to experiment
ke	Receptor endocytosis rate	0.023 s−1	Fit to experiment
[RT] = 2 × 104, K1 = 5 μM, K2 = 100 μM, and kp = 0.03 s−1			See Lemon et al. (2003a)
G-protein cascade
kdeg	IP3 degradation rate	0.01 s−1	Fit to experiment
δ	G-protein intrinsic activity parameter	0.0040	Fit to experiment
α	Effective signal gain parameter	1.1 × 10−7 s−1	Fit to experiment
ν	Cell volume	4.2 × 10−15 m3	From Fig. 4 A(d)
[GT] = 1 × 105, ka = 0.017 s−1, kd = 0.15 s−1,
[(PIP2)T] = 5 × 107, and Na = 6.02252 × 1023			See Lemon et al. (2003a)
ɛ31	Ratio of central SR to cytosolic volume	0.05	Aortal SM; Devine et al. (1972)
ɛ21	Ratio of peripheral SR to cytosolic volume	0.005	See text
βcsr, βpsr	Calcium buffering constants	0.01	See text
[Bx]	Conc. of cytosolic exogenous buffer (fluo3-AM)	10 μM	Experimental value
Kx	Fluo3-AM dissociation constant	1.1 μM	Harkins et al. (1993)
ηIP3	Permeability of IP3 channels on central SR	1.2 × 104 s−1	Fit to experiment
ηRyR	Permeability of RyRs on peripheral SR	7.2 s−1,	Fit to experiment
ηlc	Permeability of Ca2+ leak of central SR	40 s−1	Fit to experiment
ηpc	Permeability of Ca2+ pumps on central SR	2300 μM s−1	Fit to experiment
ηlp	Permeability of Ca2+ leak of peripheral SR	40 s−1	Fit to experiment
ηpp	Permeability of Ca2+ pumps on peripheral SR	230 μM s−1	Fit to experiment
kbst	Rate of RyR channel activation	1.3 s−1	Fit to experiment
τper	Time between bursts	24.5 s	From Fig. 10 A
τon	Time to start of bursts	9.3 s	See text
[(Ca2+)cyt]thr	Threshold for RyR channel activation	160 nM	See text
wdom	Domain Ca2+ weighting factor	3.1 × 10−3	Fit to experiment
[(Ca2+)T]	Total concentration of Ca2+	533 μM	Fit to experiment
d1 = 0.13 μM, d2 = 1.05 μM, d3 = 0.943 μM, d5 = 0.0823 μM,
[Be] = 150 μM, Ke = 10 μM, and k3 = 0.4 μM			See Lemon et al. (2003a)
Plasmalemmal ion currents
ηBK	Permeability of BK channels on the plasma membrane	40 pA	Fit to experiment.
kbk	Value of [(Ca2+)d] producing half-maximal activation of BK channels	2.8 μM	Canine colonic myocytes; Carl et al. (1996)
mbk	Hill coefficient of BK channels	3.2	Canine colonic myocytes; Carl et al. (1996)
Is	Membrane outward current offset	6.0 pA	From Fig. 9
Basal levels
[(Ca2+)cyt]bas = 121 nM; [(Ca2+)psr]bas = 97 μM; [(Ca2+)csr]bas = 96 μM; [G]bas = 45; and [IP3]bas = 10 nM			See text