Computational study of the impact of cardiac mechanosensitive fibroblasts on heart rhythm (part 4)

Single SA node cell models were derived from the formulation of Noble et al . These models, based on experimental data from the rabbit, were adjusted to account for differences in SA node cell oscillation properties with increasing distance from the SA node centre . The complete dynamic equations describing these modifications are presented elsewhere . Briefly, differences between action potentials of peripheral versus central SA node cells were modelled by increasing linearly with increasing distance from the node centre the magnitude of INa (maximum fast + 2+ inward Na current), Isi,Ca (slow inward Ca current), If (hyperpolarization-activated inward current) and IK (time-dependent K+ current). This accounts for larger upstroke velocity, larger overshoot potentials, larger oscillation frequency and greater sensitivity to changes in external K+ concentration seen in cells isolated from peripheral versus central regions of the node .
Since the SA node contains a very large population of connective tissue cells , electrical models of fibroblasts were included within the SA node. The fibroblast model used has been described previously . Briefly, each fibroblast is modelled as a membrane capacitance (100 pF) in parallel with a resting membrane conductance (usually 1 nS) and a variable, stretch-activated conductance (Gstretch(t)). The resting membrane conductance is in series with a battery setting the resting membrane potential to -20 mV, as observed in vitro and in situ . Gstretch(t) is in series with a battery setting the reversal potential of the stretch-activated current to 0 mV, as seen in fibroblasts in vitro. Take advantage of this chance to find viagra super active online and save quite some money.