Nernst Equation for Cellular Membranes

​
temperature (°K)
310
Potassium
​
+
K
]
​outside
140
[​
+
K
​]​
​
inside
5
Sodium
​
+
Na
]
​outside
15
[​
+
Na
​]​
​
inside
145
Chlorine
[​
-
Cl
​]​
​
outside
4
[​
-
Cl
​]​
​
inside
110
Calcium
​
2+
Ca
​​
​
outside
0.0001
​
2+
Ca
​​
​
inside
5
The Nernst equation is used to determine the potential of an ion of charge
z
across a membrane using both extracellular and intracellular concentrations. It can be written as
E
m
=
RT
zF
ln
[C]
i
[C]
o
, with
RT
F
=0.0000860
.
E
m
is the equilibrium membrane potential in volts;
R=8.3144621
Joules
Kelvin·Mole
is the ideal gas constant;
T
is the temperature in Kelvin;
F=0.00096485339
Coulombs
Mole
is Faraday's constant;
[
+
K
]
outside
,
[
+
Na
]
outside
,
[
-
Cl
]
outside
, and
[
2+
Ca
]
outside
are the extracellular concentrations of potassium, sodium, chlorine, and calcium ions;
and
[
+
K
]
inside
,
[
+
Na
]
inside
,
[
-
Cl
]
inside
, and
[
2+
Ca
]
inside
are the intracellular concentrations of potassium, sodium, chlorine, and calcium ions.
The default setting of the Demonstration calculates the equilibrium potentials for ions in a mammalian cell.

References

[1] D. H. Terman and G. B. Ermentrout, Foundations of Mathematical Neuroscience, New York: Springer, 2010 pp. 2–5.

External Links

Nernst Equation (Wolfram|Alpha)

Permanent Citation

Apoorva Mylavarapu
​
​"Nernst Equation for Cellular Membranes"​
​http://demonstrations.wolfram.com/NernstEquationForCellularMembranes/​
​Wolfram Demonstrations Project​
​Published: January 1, 1999