Biopotential

Biopotential (bioelectric potential, obsolete. Biocurrent ) is the energy characteristic of the interaction of charges located in the living tissue under study, for example, in various areas of the brain , in cells and other structures.

It is not the absolute potential that is measured, but the potential difference between two points of the tissue, reflecting its bioelectric activity, the nature of metabolic processes . Biopotential is used to obtain information about the state and functioning of various organs.

Content

Causes of occurrence

The potential difference between the excited and unexcited parts of individual cells is always characterized by the fact that the potential of the excited part of the cell is less than the potential of the unexcited part. For tissue, the potential difference is determined by the combination of potentials of individual cells.

The difference in electrical potentials in some cases plays a very important role for the vital activity of the body ( Electric stingray ), and in others it is a secondary one, being a consequence of biochemical transformations.

Action potential and rest potential

The potential of action is called the potential arising from the excitation of tissue. Usually it quickly reaches its maximum (in ~ 0.1-10 milliseconds), and then more slowly (milliseconds - seconds) decreases to zero.

Rest potential is the potential existing between the environment in which the cell is located and its contents.

Damage potential - the potential between the damaged and undamaged parts of the tissue. The damaged part of the tissue receives a negative potential in relation to the intact.

Measurement

The voltage created by muscle or nerve tissue is less than the voltage created by a single fiber due to the shunting action of extracellular fluids or connective membranes. When registering biopotentials between electrodes that divert potential, usually there is not one fiber, but a whole system of muscle or nerve fibers. The measured value of the emf remains approximately the same as that of a single fiber, but the resistance of the emf source (tissue resistance) decreases. So, the resistance of one centimeter of a single nerve fiber is several tens of Mohms, and the resistance of one centimeter of the nerve trunk is tens of ohms.

The registration of action potentials is performed by external electrodes (bipolar lead and the corresponding two-phase action potential).

Medical Diagnostics

In electroencephalography, the skin potential measured with a silver chloride electrode is compared with the potential of the electrode superimposed on this area. In this case, the biopotential is quantitatively measured by the voltage between the electrode and the conditional zero ( ground ).
Electrocardiography
Lie detector and dermal reflex (RAG)
Electrogastrography - a method for studying the motor activity of the stomach
Electistagmography (ENG)
Electromyography (EMG)
Electroreography (ERG)
Electroneurography ( ENG )
A system for the diagnosis of mastitis in cows has been developed according to the level of the biopotential of points ( BAP ) on the skin of an animal (in surface-localized biologically active centers).

Pacemakers

Pacemaker
Pacemaker

Visual manifestations of biopotentials in nature

Some animals in the body have specialized cells that can create, for defense or attack, high potential . The EMF formed in this case can reach several hundred volts :

Electric Stingray
Electric eel