Coupled biochemical reactions that act as sources of this quantity are modeled as Gerischer elements. The transepithelial form of this quantity is a common measure of tight junction barrier integrity. Gigaseals are omega-shaped regions of cell membranes for which this quantity is on the scale of 10^9 in SI units. The change in this quantity is proportional to cell volume in the mechanism of a Coulter counter. A sucrose gap creates a region where this quantity is high in an alternative (-5[1])to (*) patch clamping. The reciprocal of this quantity, written lowercase g, sometimes names the Hodgkin-Huxley model. Myelin increases this electrical quantity across the (10[1])axolemma while decreasing capacitance, thus allowing for saltatory conduction. For 10 points, name this quantity equal to resistivity times thickness over cross-sectional area, or voltage over current. (10[1]) ■END■