The crist a terminalis cell in the rabbit heart: A model

We have developed a mathematical model for a rabbit crista terminalis cell which is based on experimental results from whole-cell voltage clamp recordings as well as action potential data from enzymatically isolated single pacemaker cells. It consists of two parts, a Hodgkin-Huxley (HH) model of sarcolemma, and a fluid compartment model of the intra- and extracellular media. The HH model includes equations for the known ionic currents (INa, ICa, L, ICa, T, IK, Ito, If, IK1, ICl) in mammalian cardiac pacemaker cells, as well as the Na⁺ /K⁺ and Ca²⁺ pumps and the Na⁺ /Ca²⁺ exchanger. The fluid compartment model is based on a material balance for the ion concentrations in the intracellular medium (Na⁺, K⁺ and Ca²⁺); the concentrations are assumed to be constant in the extracellular medium. Provision is made for Ca²⁺ buffering in the intracellular medium, as well as the uptake and release of Ca²⁺ by the sarcoplasmic reticulum (SR). We simulate the functional role of each channel by discussing and comparing the model-generated results with the data. Our model is able to provide good fits to experimental data from several published sources, and therefore can be used to provide insights into the biophysical interactions of the ionic currents that generate the pacemaker potential and action potential in a rabbit crista terminalis cell.