Signal (biology)
From Freepedia
In biology a signal or biopotential is an electric quantity (voltage or current or field strength), caused by chemical reactions of charged ions whose modulation represents coded information about the biological source from which it comes. Another use of the term lies in describing the transfer of information between and within cells, as in signal transduction. Biological signals can also be seen as an example of signal (information theory).
This ionic transport within and along the excitable fibers (like nerve or muscle, including heart muscles) can be measured on the surface of the skin using a specific type of electrochemical sensor commonly referred to as the surface recording electrode (sometimes just called the electrode).
The purpose of the electrode is to act as a transducer between the ionic transport of the cell and the electron flow in the connecting metal wire. It is the junction between the electrode and the electrolyte (paste or gel made up of silver-silver chloride) that allows such a transduction to take place.
The signals coming from the heart are called ECG waves, while that from the brain are called EEG waves. Similarly, from the muscles electromyogram, from the eyes electrooculogram, from retina electroretinogram, from the cerebral cortex electrocorticogram may also be recorded.
These form intergral part of the armoury in electrophysiology studies and biofeedback experiments.
