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Ligand-gated sodium channels, on the other hand, create the change in the membrane potential in the first place, in response to the binding of a ligand to it. Leak sodium channels additionally contribute to action potential regulation by modulating the resting potential (and in turn, the excitability) of a cell. [35]
As an action potential (nerve impulse) travels down an axon there is a change in electric polarity across the membrane of the axon. In response to a signal from another neuron, sodium- (Na +) and potassium- (K +)–gated ion channels open and close as the membrane reaches its threshold potential.
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.
Sodium channels have the intrinsic ability to close rapidly following depolarization, and this current, named the "transient sodium current" is large and contributes to the bulk of the action potential.
Voltage-gated sodium channels found in mammals can be divided into three types: Nav1.x, Nav2.x, and Nav3.x. Nav1.x sodium channels are associated with the central nervous system. Nav1.1, Nav2.2, and Nav1.6 are three isoforms of the voltage-gated sodium channels that are present at high levels in the central nervous system of an adult rat brain. [5]
As a result, the action potential signal jumps along the axon, from node to node, rather than propagating smoothly, as they do in axons that lack a myelin sheath. The clustering of voltage-gated sodium and potassium ion channels at the nodes permits this behavior.
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. In parallel with the depolarisation and sodium ...
Voltage Gated Sodium (Na +) channels are significant when it comes to propagating the action potentials in neurons and other excitable cells, mostly being used for the propagation of action potential in axons, muscle fibers and the neural somatodendritic compartment. [11]