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    Hi

    Can anyone tell me when voltage-gated channels open?

    I.e., do they open during depolarisation or repolarisation, because I thought that the reversal of membrane potential caused the voltage-gated channels to open, but if the voltage-gated channels cause the action potential by opening and reversing the membrane potential then how do these channels open in the first place?

    thanks
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    anyybowdy
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    (Original post by aWildPidgey)
    Hi

    Can anyone tell me when voltage-gated channels open?

    I.e., do they open during depolarisation or repolarisation, because I thought that the reversal of membrane potential caused the voltage-gated channels to open, but if the voltage-gated channels cause the action potential by opening and reversing the membrane potential then how do these channels open in the first place?

    thanks
    The voltage (or membrane potential) at which 2 different channels open will be different. For example, a sodium channel opens with an action potential (ie when membrane potential reaches around -40mV), allowing depolarisation. But a Potassium channel opens after depolarisation, when the membrane potential is around +40mV.

    So the voltage at which it opens is dependant on the type of channel.

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    (Original post by ash92:))
    The voltage (or membrane potential) at which 2 different channels open will be different. For example, a sodium channel opens with an action potential (ie when membrane potential reaches around -40mV), allowing depolarisation. But a Potassium channel opens after depolarisation, when the membrane potential is around +40mV.

    So the voltage at which it opens is dependant on the type of channel.

    Thanks so is it the generator potential which needs to reach the threshold (-55mv) to cause the sodium channels to open?
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    (Original post by aWildPidgey)
    Thanks so is it the generator potential which needs to reach the threshold (-55mv) to cause the sodium channels to open?
    no problemo!

    Yup,
    [EDIT: deleted, I made an error there ]

    And so -55mV is called the threshold, why? Because this is the voltage (aka membrane potential) at which most of the sodium channels open (which of course are voltage-gated channels).
    As most of the sodium channels open here, depolarisation can occur up to +40mV (generally).

    So the reason a weak stimulus doesn't result in depolarisation is that it still does produce a slight rise in voltage, but not enough to open many sodium channels.

    Cool?


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    Sorry about that, pidgey


    This was posted from The Student Room's iPhone/iPad App
 
 
 
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