DEPOLARIZATION

From Big Medical Encyclopedia

DEPOLARIZATION (Latin the de-prefix extraction, decrease + polarization) — reduction or full elimination of polarization. Represents the phenomenon, the return polarization (see), also plays an important role in physical. - chemical and biol, systems. In particular, D. is the cornerstone of emergence and development of action potential.

Due to various nature of phenomenon of polarization (light, dielectric, electrochemical, fiziol, etc.) distinguish the corresponding types

of D. V of electrochemistry understand reduction or elimination of the chemical polarization of electrodes arising in most cases as a result of a hydrogen release on the cathode or oxygen on the anode as D. or owing to change konts. electrolytes about the cathode and the anode (concentration-polarization). Phenomenon of polarization — a factor often adverse. At electrolysis, e.g., D. is followed by excessive power consumption, and during the work of a galvanic cell leads to decrease in the operating EMF. Chemical polarization can be reduced, applying special substances — depolarizators. So, the polarization caused by allocation on the cathode of hydrogen is reduced, adding oxidizers (nitric to - that, potassium bichromate, manganese dioxide, etc.) - the Polarization which arose at allocation on the anode of oxygen is reduced addition of reducers (e.g., alcohol). Concentration-polarization can be reduced considerably, vigorously mixing solution or applying saturated solutions that is used, e.g., in a standard Weston cell (see. Vestona normal element ).

Along with polarization defines electrochemical oxidation and recovery of organic matters; it consists in reduction of the relation konts. the oxidized components to konts. recovered.

In physiology understand reduction of a difference of bioelectric potential between contents of a cell and the environment as D.; D.'s phenomenon is the cornerstone of development of action potential (see. Bioelectric potential , Excitement ). Can be caused by action of a number of physiologically active agents, napr, acetylcholine, etc. At the first moments of development of action potential there is an increase in permeability of a membrane for ions of sodium. It leads to the fact that sodium begins to arrive in a cell; asymmetric distribution of ions at the same time is broken, and reduction of potential difference at the first moments of development of action potential results.

See also Electrodes ,

L. G. Yaglova.

Яндекс.Метрика