A mathematical model of a rabbit sinoatrial node cell. Demir, S., J. Clark, C. Murphey, and W. Giles. Am. J. Physiol. Cell Physiol. 266: C832-C852, 1994.

Description

A mathematical model for the electrophysiological 
responses of a rabbit sinoatrial node cell that is 
based on whole cell recordings from enzymatically 
isolated single pacemaker cells at 37 degrees C has 
been developed. The ion channels, Na(+)-K+ and Ca2+ 
pumps, and Na+-Ca2+ exchanger in the surface membrane 
(sarcolemma) are described using equations for these 
known currents in mammalian pacemaker cells.  The 
extracellular environment is treated as a diffusion-
limited space, and the myoplasm contains Ca2+-binding 
proteins (calmodulin and troponin). Original features 
of this model include 1) new equations for the hyper-
polarization-activated inward current, 2) assessment 
of the role of the transient-type Ca2+ current during 
pacemaker depolarization, 3) inclusion of an Na+ 
current based on recent experimental data, and 4) 
demonstration of the possible influence of pump and 
exchanger currents and background currents on the 
pacemaker rate. This model provides acceptable fits
to voltage-clamp and action potential data and can be 
used to seek biophysically based explanations of the 
electrophysiological activity in the rabbit sinoatrial 
node cell. 

   CellML models are found at: 
models.cellml.org/cellml
The nature of CellML combined with the program trans-
lating CellML (a variant of xml) into JSim's MML gives 
a surfeit of parentheses, and unfortunately loses any 
Commments and definitions that may have been in CellML.

Equations

The equations for this model may be viewed by running the JSim model applet and clicking on the Source tab at the bottom left of JSim's Run Time graphical user interface. The equations are written in JSim's Mathematical Modeling Language (MML). See the Introduction to MML and the MML Reference Manual. Additional documentation for MML can be found by using the search option at the Physiome home page.