Question

Does current flow from positive to negative, or negative to positive? Which way does current flow across the membrane during the rising phase of the action potential? During the falling phase?

Answer 1

In beginning it was believed that the current flows from positive to negative but later it was found that it is actually from negative to positive. The electrons are the ones which seek and moves towards the positive terminal. There have been lot of new discovery which indicates that the current flows from negative to positive but still all considerations are working with the previous findings. The positive charge that comes into a cell is actually the negative movement of the current.

During the rising phase in an action potential, it is found that there is inward movement of the Na+ current. The Na+ is the main carrier which moves inside the cell during the inward current movement. The positive or cationic gates open during the rising phase in a action potential and it leads to influx of the ions due to concentration gradient of the ion and membrane potential.

During the falling phase of the action potential, it inactivates the sodium channels and opens the voltage gated potassium channels. There is high potassium concentration that leaves the cell as compared to influx of sodium ions. Hence the positive charge leaves the cell as K+ ions and this makes current flow as positive.