Question

What happens when external K+ concentration of an action potential is decreased and why does it occur?

What happens when external Na+ concentration of an action potential is decreased and why does it happen?

Answer 1

A typical voltage across cell memane is -70 mV.

Under resting potential conditions the concentration of K+ outside the cell is more as compared to inside.

When the external K+ concentration of an action potential is decreased due to opening of K+ channels, it causes hyperpolaization of the cell membrane i.e the inside of the cell becomes more negatively chaged.

Volatge gated ion channels open and generate action potential in reponse to signal from another neuron in the form of neurotransmitters.

This leads to opening of Na+ channels and Na+ cations enter inside the cell membrane. Therefore the external Na+ concentration is reduced and this leads to depolarization of the cell membrane.

The Na+ ion channel closes at the peak of the action potential and is actively transported back out of the cell membrane.