The quantities Rm, Ra, Cm, Vm, etc. that appear in the diagram
and equation are given in ohms, farads, or volts, and will
depend on the size of the compartment. In order to specify
parameters that are independent of the compartment dimensions,
specific units are used. For a cylindrical compartment, the
membrane resistance is inversely proportional to the area of the
cylinder, so we define a specific membrane resistance RM, which
has units of ohms·m². The membrane capacitance is proportional
to the area, so it is expressed in terms of a specific membrane
capacitance CM, with units of farads/m². Compartments are
connected to each other through their axial resistances Ra. The
axial resistance of a cylindrical compartment is proportional to
its length and inversely proportional to its cross-sectional
area. Therefore, we define the specific axial resistance RA to
have units of ohms·m. For a piece of dendrite or a compartment
of length l and diameter d we then have WARNING: Many treatments
of the passive properties