Quotation: “All animals that move have electricity in their bodies. Electricity is the only thing that’s fast enough to carry the messages that make us who we are. Our thoughts, our ability to move, see, dream, all of that is fundamentally driven and organized by electrical pulses. It’s almost like what happens in a computer but far more beautiful and complicated.” –(neuroscientist Rodolfo Llinas quoted in “Electricity’s spark of life” by Emily Sohn in Science News for Students, 29 September 2003).
(We note that the communication, of course, can be seen as electrical pulses when studied by discipline ’electricity’ and can be seen as mechanical pulses (solitons) when sudied by another discipline. The speed of biological electricity is million times slower that the speed of electromagnetic pulses, and matches speed of the sound in biological fluid. The waves of the fluid show electrical behavior because the waved medium contains also ions.)
The phenomenon that the body operates with electric signals was discovered about one and a half century ago [105], and the idea that ”In simple cases of ionized substances both the amount of substance and the force acting may be expressed in electrical terms” [43] shined up nearly a century ago. The basic idea of biological current was correctly defined at the beginning: ”The permeability of a membrane to a penetrating substance is given quantitatively by the amount of the substance which crosses a unit area of the membrane in unit time under the action of a unit force. In simple cases of ionized substances both the amount of substance and the force acting may be expressed in electrical terms. Then the permeability may be ultimately converted into coulombs per second for a square centimeter and a potential difference of 1 volt, which is the conductance, in reciprocal ohms, for a square centimeter” [43]. However, at that time physiologically defined fine details were not known. One must never forget that ”movement of ions across the plasma membrane results in changes of electrical potential across the membrane, and these potential changes are the primary signals that convey biological messages” [2] (using ”equivalent electrical circuits” hides that the potential changes). In this section, we proceed along the line pointed by those latter authors in Chapter 2 of their book.
We must recall that this charge is delivered chemically, i.e., it is the result of an thermoelectric process, so the concentration and the potential change simultanously. Also, the charge carriers are ions instead of electrons and the transfer mechanisms are entirely different. From purely simplistic considerations concerning the many orders of magnitude in the ratio of their size and mass, we see that the charge carriers have speeds differing by orders of magnitude, that requires revisiting the classic laws such as instant interaction (behind the ideas such as Kirchoff’s laws, Ohm’s law, ’retarded potential’). Furthermore, the ions are not fixed to isolating surfaces, and some biological ”constructions” may be active elements from the point of view of electronics: the membrane may store charge (disappears) for some period and ion channels may ”produce” charge in the measured system. Also, the molecules may dissociate and polarize under the effects of local potentials, enabling to create macroscopically different parameters such as potential and concentration, see also Onsager’s reciprocal relations [96]. In the case of living matter, we must handle thermodynamical and electrical forces simultanously. The are no ’net abstract’ cases where only electrical forces act on the ions. This feature, accompanied by the slowness and large size of the ions, requires attention and rethinking the basic notions of electricity.
We must also call attention to the dynamic behavior of charges inside living matter. Basically, they are balanced, but, and it is vital for describing the life, they can get unbalanced in a local region for shorter or longer periods. This balanced state is the basis for having a resting potential (longer), and the perturbed (unbalanced) state is the basis for creating and transferring action potential, among others. The change of those states are described by the laws of motion, and their continuous change is the life itself.
Although it is fundamentally correct that ”because dissociated ions carry electric charges, their movement is influenced not only by concentration gradients but also by electric fields”, these gradients are competing with each other and their complex interaction controls the biological processes. ”Based on thermodynamic principles, ions tend to flow from regions of high concentrations to regions of low concentrations” (see [2], page 9), furthermore, the electric gradient gets more role than presumed; see Onsager’s reciprocal relations [96]. We must never forget that ions represent both charge and mass, so a current means delivering mass and vice versa. In some cases, when precisely measuring the time course of current compared to the time course of voltage, one can experience a ’phase delay’ between them. This may inspire further research, such as inventing ’inductive’, ’capacitive’ and ’resistive’ currents in electricity; or one may believe that the system shows ’non-ohmic’ behavior in biology; that is, it cannot be described by laws of physics.
An often forgotten thought is that ”The things that neurophysiologists typically want to measure are electrical signals such as action potentials and synaptic potentials, or the membrane currents responsible for these potentials. Under ideal circumstances, the physical act of measuring a neurophysiological event would have no effect on the electrical signal of interest. Unfortunately, this is seldom the case in neurophysiology.” [2], Appendix A. We do not want to repeat the content of that appendix, except some points where we add notes, corrections or pinpointings. We add, however, that neurophysiologists make measurements in hybrid circuits, where the charge carriers are ions in one half of the circuit and electrons in the other. The conversion introduces several issues, among others delays (resulting in measuring non-matching value pairs); introducing negatively charged high-speed particles into systems having positively charged low-speed particles; intermixing inhomogenous, non-isotropic, structured matter into the systems and applying laws derived for homogeneous, isotropic, unstructured matter; applying laws derived for the ”free electron cloud” to the case of slowly moving dipole molecules.
It is worth to recall: ”Accuracy: The degree to which a measurement indicates the true magnitude of a measurable quantity. Precision: The resolution and reproducibility of a measurement; implies nothing about accuracy. A measurement can be precise without being accurate. The reverse, however, is usually not true.” [2] We add: sometimes, we measure a quantity which differs from the one we wanted to measure. Especially, if we interpret erronously what we wanted to measure and how do we measure it. That is exacly the case when the model is wrong.