Electrical Model of Membrane

The membrane can be modeled by a lumped electrical circuit for quantitative study of its electrical behaviors. First a patch of membrane without any ion channels can be simply modeled by a capacitance C (typically between 0.7 and 1 $\mu F /cm^2$) with negative charge Q stored on the inside (intra-cellular side) and equal amount of positive charge stored on the outside (extra-cellular side), and the potential difference across the capacitor represents the membrane potential V_m:

V_m=Q/C

Second, an ion channel is modeled by a resistance R which allows current to flow through. Finally the resting potential is modeled by a battery of about70 mV. Put together these three elements form a simple circuit as shown in the figure.