# Nernst and GHK equation watch

1. Could some one explain the nernst and GHK equation to me.
2. (Original post by Ben_2911)
Could some one explain the nernst and GHK equation to me.
So as far as I remember from last year, the nernst equation calculates the equilibrium potential for specific ions, ie the membrane potential at which there is no longer a net movement of that ion. For sodium it's like +55mV and for potassium it's like -70mV (I think... I may be talking out of my arse tbh). Anyway, the GHK equation takes into account all of the permeable ions moving across a membrane to calculate the equilibrium potential for a membrane (ie the membrane potential where there is no net movement of any ions). The GHK calculates the resting potential of a cell, which is usually around about the value of the equilbrium potential of potassium, since it is the most permeable ion at rest. The GHK does have limitations though, as it doesn't take into account the Na/K pump.

That's about as much as I remember from year 1 neuroscience tbh aha
3. (Original post by AortaStudyMore)
So as far as I remember from last year, the nernst equation calculates the equilibrium potential for specific ions, ie the membrane potential at which there is no longer a net movement of that ion. For sodium it's like +55mV and for potassium it's like -70mV (I think... I may be talking out of my arse tbh). Anyway, the GHK equation takes into account all of the permeable ions moving across a membrane to calculate the equilibrium potential for a membrane (ie the membrane potential where there is no net movement of any ions). The GHK calculates the resting potential of a cell, which is usually around about the value of the equilbrium potential of potassium, since it is the most permeable ion at rest. The GHK does have limitations though, as it doesn't take into account the Na/K pump.

That's about as much as I remember from year 1 neuroscience tbh aha
Thanks, with the GHK equation is the number before the log a constant as on in the lectures is always 61.
4. (Original post by Ben_2911)
Thanks, with the GHK equation is the number before the log a constant as on in the lectures is always 61.
more or less, it is RT/F, where R and F are constants and T is temperature, but given that temperature is very tightlt controlled in the body, T is pretty much constant aswell when you use the GHK equation is the context of cells

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