Question

An action potential in a nerve fiber is produced, when positive and negative charges on the outside and inside of the axon membrane are reversed, because
$A)$ More ${K^ + }$ enter the axon as compared to sodium ions leaving it.
$B)$ More $N{a^ + }$ enter the axon as compared to ${K^ + }$ leaving it.
$C)$ All ${K^ + }$leaving the axon.
$D)$ All $N{a^ + }$ enter the axon.

Answer 1

Hint: When a neuron transfers information down an axon away from the cell body, it creates an action potential. The action potential is often referred to as a "spike" or a "impulse" by neuroscientists.

Complete answer:
Special forms of voltage-gated ion channels found in a cell's plasma membrane produce action potentials. When the channels open, they cause sodium ions to flow inward, changing the electrochemical gradient and causing the membrane potential to increase even further.

As a result, more channels expand, resulting in a higher electric current through the cell membrane, and so on. The polarity of the plasma membrane is reversed as a result of the sudden influx of sodium ions, and the ion channels are quickly inactivated.

Sodium ions can no longer reach the neuron when the sodium channels close, but they are actively transported out of the plasma membrane. The electrochemical gradient is then restored by activating potassium channels, which result in an outward current of potassium ions.

To retain the cell membrane potential, cells maintain a low sodium ion concentration and a high potassium ion concentration within the cell (intracellular). The sodium-potassium pump removes one positive charge carrier from the intracellular space by sending three sodium ions out and two potassium ions in.

Therefore, the correct answer is option $(B)$ More $N{a^ + }$ enter the axon as compared to ${K^ + }$ leaving it.

Note: The difference in charge between the inside and outside of a neuron is called membrane potential, and it is caused by the unequal distribution of ions on both sides of the cell. The electrical signalling that happens between neurons is referred to as an action potential.