A Model of Electromechanical Coupling in the Small Intestine - Multiscale Computer Modeling in Biomechanics and Biomedical Engineering - page 183

V m & [Ca 2+ ] i

−20 1

−50 0.5

−70 0

1 2 3 4

I BK I LVA I Ltype I NSCC

100 0 0 0.4

0.2

50 −5

pA

−5 0

0 −10

−0.2

−50 −15 −10 −0.4

1 4 1 4 1 4 1 4

I Na I bk I ka I kr

0 0.4 10 200

0.2 5

−2 100

pA

0 0

−4 0

−0.2 −5

−6 −0.4 −10 −100

1 4 1 4 1 4 1 4

Time (s)

Fig. 2 A simulated trace of intestinal slow wave activity (V m , measured in mV), Ca 2 þ , and ion
conductances using the smooth muscle cell model (Eq. 3 ). I CaL and I LVA are calcium
conductances; I BK , I kr , I ka , I bk are potassium conductances; I Na is a sodium conductance; I NSCC
is a non-selective conductance, which is also Ca 2 þ -dependent

3.1 Continuum Model

In a continuum model of intestinal electrophysiology, the mathematical descrip-
tions of slow wave propagation incorporate activities of scales larger than that of a
single cell. In one popular approach, individual cells are modeled and integrated
over an electrical syncytium. In the early stages of cardiac modeling, such a
discrete approach was used to model networks of individual cardiac cells over
minute scales (0.5 by 1.5 mm 2 ) but involved significant computational expense
(4.5 h to simulate 520 ms of electrical activity) [ 40 ]. Even with the significant