When a certain neurotransmitter binds to its postsynaptic receptor, an ion channel opens that is about equally permeable to Na+ and K+ ions. Na+ ions flow into the muscle fiber and simultaneously, K+ ions flow out. Despite these oppositely directed currents, the postsynaptic cell is strongly depolarized. Which one of the following provides the best explanation of why this occurs? A. Outward flow of K+ ions exceeds inward flow of Na+ ions. B. The flow of Na+ ions is equal and opposite to the flow of K+ ions. C. Inward flow of Na+ ions exceeds outward flow of K+ ions. D. Na+ and K+ ions collide with one another inside the channel and the opposing currents cancel. E. None of the above is correct.
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Step 1: When the neurotransmitter binds to its postsynaptic receptor, an ion channel opens that is permeable to both Na+ and K+ ions. Show more…
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