Hodgkin–Huxley model is a mathemetical description given by Alan Hodgkin and Andrew Huxley in 1952. This is a mathematical model that represents the formation of electrical activity in neurons. This model is a set of nonlinear differential equations that approximates the electrical characteristics of neurons of squid giant axon. They received Nobel Prize in Physiology or Medicine for this work in the year 1963. HH.m implements the Hodgkin Huxley model for different applied excitations (stimulus current).
Beeler and Reuter developed a model in 1977 for cardiac muscle. This model has fast inward sodium current INa, similar to Hodgkin and Huxley model. In addition, a slow gating variable (j), a time-activated outward current (Ix1), a time-independent potassium outward current (IK1), and a secondary slow inward calcium current (Is). Plateau phase is observed in the action potential of cardiac cells which was not found in nerve cells. This is due to the inflow of calcium ions. BR.m implements the Beeler Reuter model.