Cardiac cellular electrophysiology: past and present.
The time-course of the cardiac action potential can be accounted for in terms of ionic currents crossing the cell membranes. Depolarizing current is carried by Na+ or Ca2+ entering the cells, repolarizing current by K+ leaving the cells. Membrane permeability for the passive movement of these ions is thought to be voltage-dependent as well as time-dependent. Net transfer of charge may also result from active transport, 2 Na+ out against 1 K+ in; or coupled exchange, 3 or 4 Na+ in against 1 Ca2+ out. This review follows the path by which present-day knowledge has been reached. It also gives a few examples to illustrate that electrophysiology has provided concepts useful to clinical cardiology.
D000200:Action Potentials; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D006321:Heart / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D008564:Membrane Potentials; D009206:Myocardium / Q000648:ultrastructure