Something produced from within the body itself. One type of electrodermal response, skin potential response, is produced by electrical activity generated by the dermis. Its measurement requires the placement of one electrode over an area well supplied with sweat glands (active site) and the other over an area devoid of them (reference site). The active site is negative in relation to the reference site by an amount that varies from a few to 50 to 60 mV. An alerting stimulus generally produces an increase in negative potential, followed by a positive wave, usually commensurate with the production of surface sweat, and sometimes a second negative wave. Similarly, EEG signals are generated by bioelectric processes in the brain, and EKG from the heart. For contrast, See: exosomatic.