Question

The initial depolarization of the nerve cell membrane involves the movement of ____ ions into the cell
A. sodium
B. potassium
C. chlorine
D. all of the above

Answer 1

Hint: Polarization events such as depolarization and repolarization are responsible for the conduction of nerve impulses between nerve cells.

Complete answer: When nerve cells are at rest, they have an electrical charge across their membranes, in such a way that the outside of the cell possesses positive charge and the inside of the cell possess a negative charge. Polarization events that occur, in the cell, help in the conduction of nerve impulses between nerve cells. Depolarization is said to have occurred when the nerve cell reverses these charges and gets them back to the resting state. Neurons response by undergoing depolarization in presence of stimuli such as heat, chemicals, light, electrical or physical stimulus, etc. Neurons do so by sending another electrical signal. After receiving that signal, sodium ions rush into the neuron and cause the shift in the membrane potential from negative to positive. This shift in charge from negative to positive is achieved by opening sodium and potassium channels and thus, sodium ions move inside the cell. Even if a small portion of the neuron is depolarized, this will result in generating a strong nerve impulse.
Hence, the correct answer is option A.

Note: In order to move into a cell, sodium needs special channels, because if the cell permits every ion to move into it, then the cell ultimately becomes toxic. So, to prevent this action, nerve cells regulate the entry of ions via ion gated channels. The channel is a specific protein embedded in the plasma membrane and is triggered by sodium ions.