Gating (electrophysiology)

In electrophysiology, the term gating refers to the opening (activation) or closing (by deactivation or inactivation) of ion channels.

'Inactivation' is the closing of the inactivation gate, and occurs in response to the voltage inside the membrane becoming more positive, but more slowly than activation.

[7] These voltage-dependent changes in function are critical for a large number of processes in excitable and nonexcitable cells.

[2] Voltage-gated ion channels open and close in response to the electrical potential across the cell membrane.

[16] These SNARE complexes mediate vesicle fusion by pulling the membranes together, leaking the neurotransmitters into the synaptic cleft.

[22] With this channel the correct depolarization and repolarization via chloride ions is essential for propagation of an action potential.

When the presynaptic neuron releases neurotransmitters at the end of an action potential, they bind to ligand-gated ion channels.

Ligand-gated ion channels are responsible for fast synaptic transmission in the nervous system and at the neuromuscular junction.

[23] Each ligand-gated ion channel has a wide range of receptors with differing biophysical properties as well as patterns of expression in the nervous system.

[25] Inactivation typically occurs when the cell membrane depolarize, and ends when the resting potential is restored.

The exact mechanism is poorly understood, but seems to rely on a particle that has a high affinity for the exposed inside of the open channel.

[26] Rapid inactivation allows the channel to halt the flow of sodium very shortly after assuming its open conformation.

Voltage-gated ion channels are composed of 4[dubious – discuss] α subunits, one or more of which will have a ball domain located on its cytoplasmic N-terminus.

[32] The closed conformation is assumed by default, and involves the partial straightening of helix VI by the IV-V linker.

Recent studies have suggested a molecular dynamics simulation-based method to determine gating charge by measuring electrical capacitor properties of membrane-embedded proteins.

[34] Other ion channels located in the membranes of mitochondria, lysosomes, and the Golgi apparatus can be measured by an emergent technique that involves the use of an artificial bilayer lipid membrane attached to a 16 electrode device that measures electrical activity.

An animated representation of the molecular structure of a simple ion channel
Voltage-gated ion channel. When the membrane is polarized, the voltage sensing domain of the channel shifts, opening the channel to ion flow (ions represented by yellow circles).
Calcium release causes a strong attraction between multiple proteins including synaptobrevin and SNARE proteins to pull the neurotransmitter vesicle to the membrane and release its contents into the synaptic cleft
Voltage-gated ion channel in its closed, open, and inactivated states. The inactivated channel is still in its open state, but the ball domain blocks ion permeation.
As the membrane potential returns to its resting value, the voltage differential is not sufficient to keep the channel in its open state, causing the channel to close.