Biomedical Engineering Reference
In-Depth Information
Fig. 1.
Interactions between two coupled regions with intrinsically different pacing frequencies.
a
is a diagram of the simulation system for two isolated (groups of) cells with a coupling
resistance
R
c
.
b
shows the relationship between coupling resistance and the entrained CL. The
horizontal lines indicate the intrinsic CLs for isolated cells with the normal model (
solid line
)
and the model with two times the normal L type Calcium current (
I
si
)(
dashed line
) and the
model with 1.5 times the normal
I
si
(
dotted line
).
c
shows the latency between action potentials
occurring in the two groups of cells as a function of the coupling resistance.
d
shows the
individual maximum d
V
/d
t
(
V
max
) values for the two groups of cells as functions of coupling
resistance. The
open circles
are for the aggregate with the two times normal
I
si
model. The
filled
circles
are for the aggregate with the normal model. As in (
b
), the
horizontal lines
indicate the
intrinsic
V
max
for the models as labeled. From Joyner et al. [13].
During the periods of uncoupling the spontaneous activity of cell A is occurring at
a shorter interbeat interval (IBI) (310 ms) than the spontaneous activity of cell B
(390 ms). The action potentials of the two cells are also somewhat different in shape,
with cell A (
solid line
) having a less negative maximum diastolic potential (-57 mV
vs. -62 mV) and a less positive peak amplitude (26 mV vs. 28 mV) than cell B
(
dotted
line
). Cell A also has a shorter action potential duration than cell B. The lower
panel of Fig. 2a plots the coupling current for this cell pair. The coupling current is, of
course, zero during the two periods of uncoupling, and is plotted as a positive current
in the direction from cell A to cell B. When the cells are coupled even with this small
