Human sinus node cellular electrophyisology model

Described in:
Loewe et al., Biophysical Journal 2019, "Hypocalcaemia-Induced Slowing of Human Sinus Node Pacemaking"
doi:10.1016/j.bpj.2019.07.037

Some more detail is given here:
Loewe et al., Proceedings of the 41st IEEE Engineering in Medicine and Biology Conference (2019), Berlin "Inter-Species Differences in the Response of Sinus Node Cellular Pacemaking to Changes of Extracellular Calcium"
doi:10.1109/embc.2019.8857573

Based on:
Fabbri et al., J Physiol 2017, "Computational analysis of the human sinus node action potential: model development and effects of mutations."
doi:10.1113/JP273259