Calculate the driving force on an ion as membrane potential minus equilibrium potential (Vm − Eion), or solve for either potential from the other two.
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Driving Force Formula
The following equation gives the voltage driving force for one ion, using the stated sign convention. It is not a mechanical force.
- Where Vdf is the driving force (mV or V)
- Vm is the membrane potential (mV or V)
- Veq is the equilibrium potential (mV or V)
To calculate the ion driving potential using this sign convention, subtract the ion equilibrium potential from the membrane potential. The additional vehicle, incline and rotation modes are idealized mechanical models with assumptions and formulas in their calculation details.
What is a Driving Force?
Definition:
In membrane electrophysiology, the (electrochemical) driving force for a specific ion is the difference between the membrane potential (Vm) and that ion’s equilibrium (Nernst) potential (Veq).
The ion equilibrium potential depends on its concentration ratio, charge and temperature. Driving potential depends on Vm − Eion. Conventional current Iion = gion(Vm − Eion) is outward-positive for either ion charge; anion particle motion is opposite conventional current.
How to Calculate Driving Force?
Example Problem:
The following example outlines the steps and information needed to calculate the Driving Force.
First, determine the membrane potential. In this example problem, the membrane potential is measured as −70 mV.
Next, determine the equilibrium potential. In this case, this is calculated to be −90 mV.
Finally, calculate the electrochemical driving force using the formula above:
Vdf = Vm - Veq
Vdf = (−70) - (−90)
Vdf = 20 mV
