[单选题]
The diagram shows an action pl **i vo f8h-hq;, cdxzjryp,-ondv4 )qc/0si xtential.
What is happening at point X?
A. Repolarization due to potassium ions diffusing out
B. Repolarization due to sodium ions diffusing in
C. Depolarization due to sodium ions diffusing out
D. Depolarization due to potassium ions diffusing in
参考答案: A
本题详细解析: Explanation:
When voltage-gated potassium channels open, K++ ions diffuse out down their concentration gradient, causing the inside of the neuron to become more negative. Choice A is correct.
Choice B is incorrect as when sodium ions diffuse into the neuron the membrane potential rises due to the increase in positive charge inside the neuron.
Choices C and D are incorrect as the term depolarisation means an increase in the membrane potential.
