Why is the equilibrium potential of potassium ions negative

I've just read about this question for a long time, so I can share it: first, when potassium ions form an equilibrium potential, the cell forms a resting point, and the cell's sodium channel is not open, and potassium ions can enter and exit through the leakage potassium channel. So the resting potential is equal to the equilibrium potential of potassium ions.

At this time, because the sodium-potassium pump pumps out 3 sodium and 2 potassium, the external positive and internal negative resting potential of the whole is formed. Then look at potassium ions, at this time the potassium ions in and out should be equal, that is, the net output is 0, but the intracellular potassium ions are high concentration, if you put aside the electric field driving force, it should logically flow outward, but at this time it is balanced, because the high concentration of sodium ions outside the cell also provides an external positive and internal negative electric field force to inhibit the outflow of potassium ions (remember that at this time the sodium channel is not open, sodium can not flow out,), so the force of the external positive and internal negative electric field force generated by sodium ions on potassium ions should be inward, negative! Tangled for more than an hour, to yours, the same entanglement, share, hope!

The concentration of K ions outside the membrane < the concentration of K ions in the membrane, so the main ion flow in the resting phase is the outflow of potassium ions, which leads to the transfer of positive charge outward, so that the positive charge in the cell decreases and the positive charge outside the cell increases, and the cell membrane.

The lateral potential is increased and the inner potential of the cell membrane is decreased. As potassium ions flow out along the concentration difference, it forms an electric field force that is negative inside and positive outside.

It prevents the positively charged potassium ions from continuing to flow out. When the force created by the concentration difference that causes the outflow of potassium ions is balanced with the force of the electric field that prevents the outflow of potassium ions, the net movement of potassium ions is equal to zero. At this point, there is a stable potential difference between the two sides of the cell membrane.

The equilibrium potential called potassium ions.

When the cell is at rest, the membrane opens up ungated potassium channels (ignoring the entry and exit of sodium ions in such channels), and potassium ions can enter and exit the cell across the membrane. Due to the existence of potassium-sodium pump, the concentration of potassium ions in the cell is much higher than that of the outside of the cell, and this concentration difference causes the outflow of potassium ions (note that only a small part of the outflow is out, and the potassium ions in the membrane are still much more than those outside the membrane), and the outflow of potassium ions forms a galvanic layer on the outer surface of the cell membrane, and the electrogenesis effect of the sodium-potassium pump makes the outside of the membrane positively charged, resulting in the formation of a positive and negative potential difference between the outside and the inside, and this potential difference can just offset the driving force of potassium ions flowing outside the membrane due to the concentration difference, and the cell will reach a resting state. The potential difference at this point is called the equilibrium potential.

The result of the calculation of the equilibrium potential of potassium ions derived from the Nernst equation should be positive inside and negative on the outside. The side with the highest concentration of cations in the most ** state of the element is the positive electrode of the concentration cell, and the side with the small concentration is the negative electrode. The formula in the textbook calculates the correct values, but the symbols are wrong.

For details, please refer to the article "Bioelectricity and Membrane Potential" written by Wang Xiaoen, Spark of Scientific Wisdom of the Chinese Academy of Sciences**.