Question

Action potential of a nerve cell is generated by
A) $Na^+$
B) $K^+$
C) $Ca^+$
D) $Cl^ -$

Answer 1

Hint: Action potential is the mode through which nerve cells transmit electrical impulses. The change in the voltage in the membrane is due to the movement of ions in and out of the neurons.

Complete Answer:
The value of resting membrane potential of neurons depends on the types of ion channels that are open and the concentration of ions in the intracellular and extracellular fluids. In neurons, the K+ is present at higher concentration inside the cell whereas sodium and chloride ions are found in higher concentration outside the cell.
Action potential is generated by voltage gated ion channels of the plasma membrane. These channels open when the membrane potential increases in accordance with the threshold value. The repolarization takes place due to the positive charge of sodium ion, the channel open. The Na+ moves inward which increases the membrane potential.
The potassium channel opens a little later. The potassium ion rushes out of the cell. This is called repolarisation.

Thus the correct answer is (A). Action potential is generated due to sodium ions.

Note: The resting potential of the membrane is -50 to -75mV. This concentration gradient is maintained by the action of sodium/potassium ions. The active transport of these ions helps in maintaining the membrane potential. Every action potential is followed by a refractory period.