Sodium voltage-gated ion channels

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A Sodium voltage-gated ion channel is a type of protein found embedded in the plasma membrane of cell, more specifically, nerve and muscle cells .

Role in an Action Potential

The voltage gated sodium ion channels are responsible for the influx of sodium into a neurone causing depolarisation of the membrane and therefore an action potential. Voltage gated soium ion channels have three states:

  1. closed
  2. open
  3. inactive.

Voltage-gated sodium ion channels open when a membrane is depolarised from its resting membrane potential (-70 mV). Depolarisation only occurs when the voltage across the plasma membrane increases above a certain threshold (-55 mV). When the membrane is fully depolarised, and the action potential is at its peak, the channels inactivate themselves by closing the inactivation gate. During inactivation, the voltage-gated sodium ion channel is unable to be stimulated by depolarisation of the membrane so an action potential cannot be created. When the voltage across the membrane reduces to a low enough value the inactivation gate opens and the activation gate closes so the channel is again able to be stimulated by depolarisation of the membrane.

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