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Bioelectric effects were known in ancient times from the activity of such electric .... cell bioelectr

Bioelectric effects were known in ancient times from the activity of such electric fishes as the Nile catfish and the electric eel. In nearly all cases, however, a bioelectric current consists of a flow of ions ( i.e., electrically charged atoms or molecules), whereas the electric current used for lighting, communication, or power is a movement of electrons. In most solutions, ions of a given electric charge are accompanied by ions of opposite charge, so that the solution itself has no net charge. The bioelectric potential across a cell membrane is typically about 50 millivolts; this potential is known as the resting potential. All cells use their bioelectric potentials to assist or control metabolic processes, but some cells make specialized use of bioelectric potentials and currents for distinctive physiological functions. In nerve and muscle cells, chemical or electrochemical stimulation results in temporary changes in the permeability of cell membranes, allowing the elec! tric potential between inside and outside to discharge as a current that is propagated along nerve fibres or that activates the contractile mechanism of muscle fibres. Among other cells in which specialized functions are dependent on the maintenance of bioelectric potentials are the receptor cells sensitive to light, sound, and touch and many of the cells that secrete hormones or other substances. The electric catfish of Africa, the knife fish of Latin America, and the stargazers probably use their bioelectric organs as sense organs in the detection of other fishes. cell bioelectr

posted by car-toyota @ 10:03 AM