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For the voltage-gated sodium channel to allow sodium into the cell:_______.
a. the activation and inactivation gates must both be open
b. only the activation gate must be open
c. only the inactivation gate must be open
d. the inactivation gate must be closed shortly before the activation gate opens
e. the activation and inactivation gates must both be closed


Sagot :

Answer:

The correct option is - (a) the activation and inactivation gates must both be open.

Explanation:

Option (a) is correct because of the following reason -

The axonal membrane is at its natural resting potential until an action potential occurs, and [tex]Na^+[/tex] channels are deactivated and blocked on the extracellular side by their activation gates. The activation gates open in response to an electric current, allowing positively charged [tex]Na^+[/tex] ions to flow into the neuron through the channels. When enough [tex]Na^+[/tex] has penetrated the neuron and the membrane potential has reached a certain level, the [tex]Na^+[/tex] channels inactivate themselves by closing their inactivation gates at the height of the action potential. The inactivation gate can be thought of as a "plug" tethered to the intracellular alpha subunit's domains III and IV. When the inactivation gate is closed, the flow of [tex]Na^+[/tex] through the channel is stopped. As a result, both the activation and inactivation gates must be open to enable sodium ions to enter the cell.

Hence , the correct option is (a).