Voltage-gated ion channel

2017-12-06T09:09:04Z

170114132: A new page on voltage-gated ion channels with an overview of what they are, their functions and in depth detail about their role in propagation of nerve impulses.

[1]A voltage-gated ion channel is a membrane residing protein, the function of which being to control the diffusion of specific ions down their concentration gradient. The main ions are namely K+, Na+, Ca2+ and Cl-. They connect the exterior to the [[Cytosol|cytosol]] with narrow passages that facilitate rapid movement due to the opening and closing of gates which are dependant on changes of transmembrane voltage. Voltage gated ion proteins have absolute [[specificity|specificity]] in the sense that they only allow passage of one ion.[2]These ion channels have a crucial job in maintenance of [[Homeostasis|homeostasis]] and the initiation and proliferation of [[Nerve_impulse|nerve impulses]].

== Nerve impulses ==

A nerve impulse is initiated because of the initiation of a change on the membrane potential, caused by the change in membrane potential from the opening and closing of sodium and potassium voltage-gated ion channels. When a [[Graded_potential|graded potential]] is large enough to reach threshold voltage, an action potential is initiated. When the membrane potential reaches -55mV, enough Na+ voltage gated ion channels have been activated by the activation of the activation gate to facilitate the [[Diffusion|diffusion]] of Na+ ions into the axon. The movement of positive ions inwards causes K+ ion channels to open and the inactivation gates of sodium channels to cause sodium channels to begin to close. As potassium channels open, sodium channels close resulting in [[Hyperpolarisation|hyperpolarisation]] of the cell membrane to a voltage of around -90mV. At this membrane potential, the potassium ions then begin to be inactivated. When both channels are inactivated there is a refractory period meaning that the ion channel cannot be reactivated, allowing for the directional [[Depolarisation|depolarisation ]]down the axon.

=== References ===

[1] Alberts; Johnson; Lewis; Raff; Roberts; Walter; Molecular biology of the cell, Fifth edition, Garland science, 2008.

[2] http://ieeexplore.ieee.org/abstract/document/1402408/?reload=true

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Voltage-gated ion channel