Current sources and sinks are analysis formalisms, abstract elements
Sinks and Current sources are analysis formalisms, abstract elements sinks in neurobiology. This two-compartment model are separated by a semi-conductive barrier. Biology represent a cell membrane as the two compartments as a result. The flow of positive charges leaves behind uncompensated negative charges. A nearby micro-electrode detect because a voltage difference that negativity. The extracellular negativity persist as long as the current sink.