The article discusses several equivalent circuits constructed by sequentially connecting circuits for the membrane and protoplasm. The solution was made using the Cardano formula for cubic equations. The roots in the expression for the determination of resonant frequencies determined the resonant frequencies for the given parameters for the membrane and intercellular fluid; to obtain numerical values, values ​​were used within several permissible limits. In the course of the calculations, it was confirmed that most resonant frequencies are in the millimeter and submillimeter ranges. It is also shown that the cell vibration frequencies occupy the decimeter, centimeter, millimeter and submillimeter wavelengths. Obviously, it is the impact on biological systems of electromagnetic radiation in the indicated wavelength ranges that will be most effective and can lead to a maximum biological response (effect).

Keywords: equivalent equivalent circuit, biological structure, membrane, oscillatory circuit, Cardano formula, protoplasm, resonant frequencies, electrical processes, equivalent equivalent circuit, electromagnetic radiation