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Voltage-gated sodium channels (VGSCs), also known as voltage-dependent sodium channels (VDSCs), are a group of voltage-gated ion channels found in the membrane of excitable cells (e.g., muscle, glial cells, neurons, etc.) with a permeability to the sodium ion Na +. They are the main channels involved in action potential of excitable cells.
Voltage-gated ion channels are often specific to ions, including Na +, K +, Ca 2+, and Cl −. Each of these ions plays an important role in the electrical behavior of the cell. [9] The gates also have unique properties with important physiological implications. For example, Na + channels open and close rapidly, while K + gates open and close ...
In neuroscience, ball and chain inactivation is a model to explain the fast inactivation mechanism of voltage-gated ion channels. The process is also called hinged-lid inactivation or N-type inactivation. A voltage-gated ion channel can be in three states: open, closed, or inactivated.
Ion channels may be classified by gating, i.e. what opens and closes the channels. For example, voltage-gated ion channels open or close depending on the voltage gradient across the plasma membrane, while ligand-gated ion channels open or close depending on binding of ligands to the channel. [14]
Voltage-gated ion-channels are usually ion-specific, and channels specific to sodium (Na +), potassium (K +), calcium (Ca 2+), and chloride (Cl −) ions have been identified. [1] The opening and closing of the channels are triggered by changing ion concentration, and hence charge gradient, between the sides of the cell membrane.
Ion channels are typically categorised by gating mechanism and by the ion they conduct. Note that an ion channel may overlap between different categories. Some channels conduct multiple ion currents and some are gated by multiple mechanisms. Examples of targets for modulators include: Voltage-gated ion channels. Calcium channel: see also ...
It is linear, indicating no voltage-dependent gating of the potassium ion channel. The yellow line shows the I–V relationship for the sodium ion. It is not linear, indicating that the sodium ion channel is voltage-dependent. The green line indicates the I–V relationship derived from summing the sodium and potassium currents.
The open sodium channels allow more sodium ions to flow into the cell and resulting in further depolarisation, which will subsequently open even more sodium channels. At a certain moment this process becomes regenerative ( vicious cycle ) and results in the rapid ascending phase of action potential.