Which is most directly responsible for the falling (repolarizing)phase of the action potential?
A)Voltage-gated Na⁺ channels are opened.
B)The Na⁺,K⁺ pump restores the ions to their original locations inside and outside of the cell.
C)The permeability to Na⁺ increases greatly.
D)ATPase destroys the energy supply that was maintaining the action potential at its peak.
E)The permeability to K⁺ increases greatly while that to Na⁺ decreases.

Question

Which is most directly responsible for the falling (repolarizing)phase of the action potential?
A)Voltage-gated Na⁺ channels are opened.
B)The Na⁺,K⁺ pump restores the ions to their original locations inside and outside of the cell.
C)The permeability to Na⁺ increases greatly.
D)ATPase destroys the energy supply that was maintaining the action potential at its peak.
E)The permeability to K⁺ increases greatly while that to Na⁺ decreases.

Quizplus · Accepted Answer

The falling (repolarizing) phase of the action potential is caused by the increase in the permeability to K⁺ ions, while that to Na⁺ ions decreases. This causes K⁺ ions to move out of the cell, leading to a decrease in the membrane potential, and thus the repolarization of the cell membrane. Therefore, option E is the correct choice.

Which Is Most Directly Responsible for the Falling (Repolarizing)phase of the Action