Depolarisation

Depolarisation (pronounced: dee-poh-lahr-ih-zay-shun) is a fundamental process in the physiology of cells, particularly in neurons and muscle cells. It refers to the change in a cell's membrane potential that makes it more positive, or less negative.

Etymology

The term "depolarisation" comes from the prefix "de-", meaning "removal of" or "reverse of", and "polarisation", which refers to the state of having distinct and opposite charges. In the context of cell physiology, depolarisation refers to the removal or reversal of the cell's resting membrane potential.

Process

Depolarisation typically begins when positively charged sodium ions rush into a neuron or muscle cell through sodium channels in the cell membrane. This influx of positive charge makes the inside of the cell less negatively charged relative to the outside, a state that is referred to as depolarised.

Depolarisation is a critical step in the generation of action potentials, which are the electrical signals that neurons use to communicate with each other and with muscle cells. In muscle cells, depolarisation triggers the release of calcium ions, which initiate the process of muscle contraction.

Related Terms

Hyperpolarisation: The opposite of depolarisation, hyperpolarisation is a change in a cell's membrane potential that makes it more negative, or less positive.
Repolarisation: The process by which a depolarised cell returns to its resting membrane potential.
Action potential: The electrical signal generated by neurons and muscle cells, which is initiated by depolarisation.
Sodium channels: Protein structures in the cell membrane that allow sodium ions to enter the cell, causing depolarisation.
Calcium ions: Positively charged particles that are released in muscle cells in response to depolarisation, triggering muscle contraction.