Question

Define depolarization, repolarization, and the action potential.

Short answer

Depolarization occurs when sodium ions enter the cell and convert the inner charge to positive.

Repolarization occurs when sodium ions escape, shifting the inner charge from positive to negative.

A voltage pulse is produced due to this process, referred to as the action potential.

Step-by-step solution

Definition of depolarization

The inner membrane of a cell usually has a negative charge, whereas the outer membrane has a positive charge.

The resting potential is a potential difference that prevents positive sodium ions from entering the cell.

The sodium gate opens (becomes permeable to sodium) when a stimulus passes through the cell membrane, allowing ions to enter the cell due to their attraction to the inner negative charge.

Depolarization is the process of turning the negative charge of the inner cell into a positive charge.

Definition of repolarization and action potential

Because they are drawn by the negative outer membrane created by a lack of positive sodium ions, this positive charge closes the sodium gate. It causes the potassium ions to depart the cell.

This results in a deficiency of positive ions inside the cell, causing the inner membrane to revert to a negative state, a process known as repolarization.

When a stimulus passes across a membrane, it creates a movement shift in the outer membrane potential from positive to negative to positive again (opposite of the inner membrane), which is effectively a traveling voltage pulse termed the action potential.