The main source of bioelectric processes in the body are cell membranes. The idea of ​​cell membranes as generators of electrical reactions appeared at the beginning of the twentieth and has since developed into a universally recognized scientific concept. Its main postulate is that the electrical reactions of various cells are the result of changes in the difference in ion concentrations on both sides of the semipermeable membrane. There is a simple mathematical expression (the Nernst equation or its modifications), according to which the value of the membrane potential is defined as the ratio of the logarithm of the concentration of ions inside and outside the membrane, and the membrane must be permeable to potential-forming ions:

E = RT / nF log C 1 / C 2, where R is the gas constant; T is the absolute temperature; F – Faraday constant; n is the valence of ions; / C is the ratio of the concentrations of potential-forming ions on both sides of the membrane. At a temperature of 20 C o the ratio RT / nF is numerically equal to 58 mV.

If two solutions with different ion concentrations are separated by a membrane that is permeable to positively charged ions (cations), but slightly permeable to negatively charged ions (anions), then cations will diffuse from a higher concentration space into a more dilute solution. After passing through the membrane, cations will be held next to it due to electrostatic attraction from the anions on its other surface. As a result of these processes, a potential difference is formed on the membrane, and the space filled with a solution with a higher concentration will be negatively charged with respect to the less concentrated solution. An example of the formation of the membrane potential is presented in the case when the membrane, which is well permeable to H + ions but poorly permeable to Cl – ions , separates concentrated and dilute HCl solutions. H + ions diffuse from a more concentrated solution to a more diluted one and are held close to the membrane due to electrostatic attraction from the Cl – ions . Due to this, the space filled with a concentrated HCl solution will be negatively charged with respect to the diluted solution. By this mechanism, the membrane potentials of nerve cells are created, where the main potential-forming cations are potassium ions. The potential difference of many other formations (cells and blood vessels) are formed according to the same principle

local_offerevent_note September 20, 2019

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