Essential knowledge

malmivu3The Bioelectro- and- bioelectromagnetism -book-NOBEL Prize, RAGNAR GRANIT

“Why should we consider the study of electric and magnetic phenomena in living tissues as a separate discipline? The main reason is that bioelectric phenomena of the cell membrane are vital functions of the living organism. The cell uses the membrane potential in several ways. With rapid opening of the channels for sodium ions, the membrane potential is altered radically within a thousandth of a second. Cells in the nervous system communicate with one another by means of such electric signals that rapidly travel along the nerve processes. In fact, life itself begins with a change in membrane potential. As the sperm merges with the egg cell at the instant of fertilization, ion channels in the egg are activated. The resultant change in the membrane potential prevents access of other sperm cells.

Electric phenomena are easily measured, and therefore, this approach is direct and feasible. In the investigation of other modalities, such as biochemical and biophysical events, special transducers must be used to convert the phenomenon of interest into a measurable electric signal. In contrast electric phenomena can easily be directly measured with simple electrodes; alternatively, the magnetic field they produce can be detected with a magnetometer.

In contrast to all other biological variables, bioelectric and biomagnetic phenomena can be detected in real time by noninvasive methods because the information obtained from them is manifested immediately throughout and around the volume conductor formed by the body. Their source may be investigated by applying the modern theory of volume sources and volume conductors, utilizing the computing capability of modern computers. (The concepts of volume sources and volume conductors denote three-dimensional sources and conductors, respectively, having large dimensions relative to the distance of the measurement. These are discussed in detail later.) Conversely, it is possible to introduce temporally and spatially controlled electric stimuli to activate paralyzed regions of the neural or muscular systems of the body.

The electric nature of biological tissues permits the transmission of signals for information and for control and is therefore of vital importance for life. The first category includes such examples as vision, audition, and tactile sensation; in these cases a peripheral transducer (the eye, the ear, etc.) initiates afferent signals to the brain. Efferent signals originating in the brain can result in voluntary contraction of muscles to effect the movement of limbs, for example. And finally, homeostasis involves closed-loop regulation mediated, at least in part, by electric signals that affect vital physiologic functions such as heart rate, strength of cardiac contraction, humoral release, and so on.”
JAAKKO MALMIVUO – Ragnar Granit Institute Tampere University of Technology