Depolarization

Depolarization is a process during the action potential of neurons where the negative internal charge of the cell temporarily becomes more positive (less negative). This shift from a negative to a more positive membrane potential occurs during several processes, including an action potential. The opposite of a depolarization is called a hyperpolarization.

Mechanism

Depolarization is caused by changes in ionic concentrations on either side of the cell membrane. The process of depolarization is entirely dependent on the intrinsic electrical nature of most cells. When a cell is at rest, the cell maintains what is known as a resting potential. The resting potential generated by nearly all cells results in the interior of the cell having a negative charge relative to the exterior of the cell.

Role in Neurons

In neurons, depolarization is often caused by positively charged ions (such as sodium or calcium) moving into the cell, or negatively charged ions (such as potassium) moving out of the cell. The influx of ions that occurs during an action potential is an example of depolarization.

Role in Cardiac Muscle Cells

In cardiac muscle cells, depolarization results from the opening of voltage-gated ion channels. These allow sodium ions to rush into the cell, causing the intracellular environment to become more positive.

See Also

• Hyperpolarization
• Resting potential
• Action potential
• Neuron
• Cardiac muscle

References

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