The active fiber in a volume conductor.
D000200:Action Potentials; D002462:Cell Membrane / Q000502:physiology; D006801:Humans; D008564:Membrane Potentials; D008954:Models, Biological; D008959:Models, Neurological; D009431:Neural Conduction; D009474:Neurons / Q000166:cytology / Q000502:physiology*