Neurons use a quasi-hidden background energy production and state restoration process which works in parallel with the neuronal functional operation with a quasi-permanent speed. The ATP is produced and delivered to the spot by independent subsystems. The ATP’s delivery, similarly to that of the ions, obeys its component gradient. When the neuron’s membrane (through the AIS, resting ion channels, and pumps) ’loses’ ions, their local gradients in the vicinity of the membrane decrease. The interesting processes (ionization, ion absorption, and so on) occur near to the membrane. The processes enable producing ’fresh’ ions from the available neutral molecules by hydrolyzis to restore their concentration; then new ATP diffuses in the place of the ’used’ ones. Those ions build up onto the membrane, increase its electrical potential. That energy is a kind of potential energy and enables to forward ions to the other segment (their presence slightly increases the potential there), while part of the energy dissipates when the ionic gradients move the ions in the viscouos fluid.
As discussed in section 2.6.5, outside the lipid bilayer, electric and concentration gradiens exist. They enable the ions to move, but since their speed is proportional to the resultant gradient, at different locations the speed of the macroscopic move of ions as well as the individual speed of ions along their path can change several orders of magnitude, from the drift speed to the potential-accelerated speed, while they travel a nanometer-long path under nanosecundum periods. For example, a ion is in rest (has the drift speed) on the high-concentration side when the ion channel gets open, accelerates to a potential-accelerated speed, than brakes down to the drift speed again on the low-concentration side. Even, its velocity components in directions parallel and perpendicular to the membrane’s surface can differ by orders of magnitude when the electrical field exert on it in the mentioned directions. The ion-gradient-related movement needs special care, since the driving force is different for the different chemical elements, and the movement of ions in close vicinity to each other (such as in ion channels) strongly affect each other.