In a segmented electrolyte we experience different forces, furthermore, the electrical fields have different sources. For a closed system, the electrical charges are balanced, but locally they may be unbalanced due to physical reasons. In a steady state, some other force must counterbalance the mentioned forces. That force may be a mechanical one: the ions sitting on the surface of the membrane press the surface due to the attractive force on ions and the membrane mechanically provides the needed counterforce. In addition, due to a concentration gradient, a thermodynamic force may act on the ions.
When any inhomogeneity is present (an ion is forcefully moved, by investing energy, to a place other than the one which is needed to be in a steady state), the ions may move due to different reasons, which, per definitionem, means current (and means potential energy). Notice the important aspect that, at a microscopic level, moving an ion simultaneously means redistributing charge and mass. At a macroscopic level, it results in simultaneous changes in the local macroscopic characteristics such as concentration and potential. These observations are expressed by Onsager’s reciprocal relations [96].
That means when describing an ionic transfer process, we must not separate the electrical current from the mass transfer: they happen simultaneously, and mutually trigger each other. Notice that the thermodynamic term is ion specific, while the electrical term is not. To be entirely balanced, the system must be balanced to all elements. In this way, changing one concentration implicitly changes all other concentrations and the electrical field.
It is a huge mistake to introduce equivalent electrical circuits with their fixed-voltage voltage generators. It forces one to assume that the conductances of the players (membrane, synapses, AIS) change without any reason, and prevents understanding how the competition of the thermodynamic and electrical processes govern neuronal operation. It leads, among others to attributing conductance change to membranes which are simple isolators with no charge carriers that could implement charge transfer, see section 2.5.3. This assumption neglects the driving force the mentioned forces provide. Instead, it attributes the magic ability to the ion channels that they can change their transmission ability as the actual situation requires, without having driving force. This approach obscures that biological electricity is of thermodynamic origin, and block understanding neuronal operation, that is the brain’s understanding.