When comparing Eq. (2.43) describing the operation of a simple serial oscillator taken from the theory of electricity, Eq. (2.74) describing HH’s differential equation (having PID in mind), and the complete Eq. (2.73) describing neuron-specific PID, one can see that they describe the same process in different (experimental and mathematical) approximations. As experience shows, Eq. (2.43) describing the ’net electric’ model provides a sufficiently accurate description of the AP, proving that the dominating effect comes from the derivate term and that the thermodynamic term is linearly proportional to the electric one. Furthermore, as we emphasized by discussing the physical processes and the mathematical terms, to some measure, the ”parallel circuit” is also present in the process, although its current amplitude is by two orders of magnitude lower than that of the ”serial circuit”; furthermore, the time constants of the two circuits are also largely different, making the effect of the parallel circuit unnoticeable. The slow current also play a role: the ion currents are ’local’: given that the channels in the membrane’s wall are always open, the current on its way towards the AIS may flow out through a nearby ion channel, so only a fragment of the ’resting current’ reaches the AIS. Eq. (2.73) provides a high-accuracy description of the process, but for most practical applications using Eq. (2.43) provides sufficiently good results, while Eq. (2.74) is based on an incorrect ’physical model’ and requires a series of incorrect ad-hoc hypotheses to describe observations. Note that the forces acting on ions have both electrical and thermodynamic components, but they are proportional to each other. That is, although the absolute values of the coefficients in the equations are not accurate; their effects are. Surely, the description of the process is complicated, but appropriate approximations give sufficiently precise and computationally reasonable results.