Table II Units of the passive membrane. Modified from Paul Sajda (2002)
Symbol |
SI units |
Physical meaning |
Notes |
Ra |
^ω |
Axial (intracellular) resistance |
For a segment of cable |
Re_____ |
^ω |
Extracellular resistance | |
Rm___ |
^ω |
Membrane resistance | |
Cm___ |
F |
Membrane capacitance | |
_ri_______ |
Ω∕m |
Cytoplasmic resistivity |
For unit length of cable |
re______ |
Ω∕m |
Extracellular resistivity | |
rm____ |
Ω.m |
Membrane resistivity | |
cm____ |
F/m |
Membrane capacitance | |
Ra |
Ω.m |
Specific axial resistance |
For unit length and unit |
RE |
Ω.m |
Specific extracellular resistance | |
Rm___ |
Ω.m2 |
Specific membrane resistance | |
Gm___ |
S.m-2 |
Specific membrane conductance | |
CM |
F/m2 |
Specific membrane capacitance | |
Vm |
V |
Transmembrane voltage |
These physical parameters are linked according to the following equations:
where d is the diameter of the neural projection and l is its length.
(56)
(57)
(58)
Rm
=ril=
RM
πdl
RA
Cm=cml=πdlCM
34