Rapid depolarization phase of action potential is due to opening of:
Answer: C) Voltage-gated Na+ channels. For Action potential, once you lock onto the key mechanism or definition, Voltage-gated Na+ channels is the clear fit. If you restate the concept in your own words, cause and effect line up with Voltage-gated Na+ channels — that is the mechanism or reason the stem is pointing to. So Voltage-gated Na+ channels is the clean, accurate selection. If a similar stem appears later, start from the same core fact and you will land on the same kind of answer. In class notes, highlight this same phrase next to the related diagram so the wording and the picture reinforce each other.
Ref: Animal physiology is Unit 7 of the CSIR NET Life Science Syllabus, covering core body systems. It accounts for roughly 10% of the total marks in Sections B and C.