Depolarization (neuroscience)

Depolarization is a reduction in the voltage difference across a cell membrane, making the cell’s interior less negative relative to its exterior. In neurons, it can bring the membrane toward the threshold for an action potential.

Resting membrane potential: The voltage difference across a cell membrane when the cell is not actively signaling. It is the baseline voltage from which neuronal depolarization begins.
Membrane potential: The electrical voltage difference between the inside and outside of a cell membrane. Depolarization is a change in this voltage toward a less negative interior.
Excitatory postsynaptic potential: A graded postsynaptic voltage change that makes an action potential more likely. It is a common local depolarization produced when excitatory synapses open ion channels.
Hyperpolarization: An increase in membrane voltage magnitude that makes a cell’s interior more negative relative to its exterior. It moves membrane voltage in the opposite direction from depolarization.
Sodium channel: A membrane protein that selectively allows sodium ions to cross a cell membrane. Opening voltage-gated sodium channels drives the rapid depolarization of an action potential.
Electrochemical gradient: The combined effect of an ion’s concentration difference and electrical forces across a membrane. It determines whether ions entering or leaving a neuron will depolarize it.
Neurotransmitter: A chemical messenger released by a neuron to affect a target cell. Some neurotransmitters open postsynaptic channels that produce depolarizing responses.
Repolarization: The return of membrane voltage toward its resting level after depolarization. It reverses the voltage change that defines depolarization during an action potential.
Potassium channel: A membrane protein that selectively allows potassium ions to cross a cell membrane. Potassium currents shape depolarization and help restore the membrane voltage afterward.
Ion channel: A membrane protein that forms a selective pathway for ions to cross a cell membrane. Depolarization depends on changing ion flow through these membrane pathways.

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