Interaction & Interdependence C.5 Neural Signaling (id: 5636ef939)

本题目来源于试卷: Interaction & Interdependence C.5 Neural Signaling，类别为 IB生物学

[单选题]
The graph below shows m -sirzsc:r4j. l 1j1ziembrr8nma240i boi ane voltage over time during an action potential. Which letter represents the segment of the action potential when voltage-gated sodium cha2 rmaoi80ni b4nnels are open and voltage-gated potassium channels are closed?

A.
B.
C.
D.


参考答案:  B


本题详细解析:

Explanation​:

Once a neuron reaches threshold potential, the voltage-gated sodium channels in the membrane open. Once these channels are open, sodium diffuses down its concentration gradient into the cell. The rapid influx of positively charged sodium ions depolarizes the cell to a positive voltage. The point marked B on the graph indicates the depolarization phase, so corresponds to the time during the action potential in which voltage-gated potassium channels are closed and voltage-gated sodium channels are open.

Between the resting potential and threshold potential (Choice A), both voltage-gated sodium and potassium channels are closed. During the repolarization phase (Choice C), voltage-gated potassium channels are open and voltage-gated sodium channels are closed. During the hyperpolarization phase (Choice D), voltage-gated sodium channels are closed and voltage-gated potassium channels are in the process of closing.

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