The inward flow of sodium ions increases the concentration of positively charged cations in the cell and causes depolarization, where the potential of the cell is higher than the cell's resting potential. The sodium channels close at the peak of the action potential, while potassium continues to leave the cell.
The cell membrane is <u>the </u><u>boundary</u><u> of</u><u> the</u><u> </u><u>cell.</u><u> </u>The outer layer of the cell (plant cells have cell wall but cell membrane is also there) which protects it is known as the cell membrane. Cell membrane is semi permeable because it has to make available the passage of water & other gases. The marked area in the attached figure is the cell membrane.
