Practice question

Answer: C) Fast Na+ channel. For Cardiovascular System: Heart, once you lock onto the key mechanism or definition, Fast Na+ channel is the clear fit. If you restate the concept in your own words, excitable-cell physiology turns on membranes, ions, and signalling steps, and Fast Na+ channel captures the correct piece of that story. So Fast Na+ channel 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.