Question

The Nernst equation for the equilibrium potential of an ion(in this case potassium),Eeq,K+=RTzFln[K+]o[K+]iEeq,K+=RTzFln⁡[K+]o[K+]iincludes the ratio of the concentration ofthat specific ionoutside of the membrane to the concentration inside. If this is for calculating the diffusional force, why does it ignore other ions? Wouldn't the concentration of other ions inside and outside of the cell also affect this ratio? For example, some ion might be more abundant inside the membrane than the outside, but some other particle might be more abundant outside, thus creating no diffusional force. However, in the equation this will be taken as if this does indeed generate a force, since it only takes into account the ion more abundant inside. Just add up everything of interest. For example, you can include sodium as which gives you chlorides, and everything else could be further added in a similar fashion, although likely to diminishing effects. These equations and numbers are from page 107-108 ofFrom Neuron to Brain.

Answer 1

The Nernst equation for the equilibrium potential of an ion, such as potassium, only considers the ratio of the concentration of that specific ion outside of the membrane to the concentration inside. Other ions are not taken into account because the focus is on the diffusional force of potassium ions specifically.

Step-by-step explanation:

The Nernst equation is used to calculate the equilibrium potential of an ion, in this case potassium. It considers the ratio of the concentration of potassium ions outside of the membrane to the concentration inside the membrane. Other ions are not taken into account because the focus is on the diffusional force caused by the concentration gradient of potassium ions specifically. The equation assumes that the concentration of other ions is balanced and does not have a significant impact on the diffusional force of potassium ions.