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Korolos_5348
#1 Posted : Wednesday, July 15, 2020 9:59:59 PM
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Hello,

I just came across a question I found confusing and I was wondering if someone could confirm if my understanding is correct. The stem is

"Which of the following changes would NOT interfere with the repeated transmission of an impulse at the vertebrate neuromuscular junction?"

The answer choices are

A. Addition of a cholinesterase blocker
B. Addition of a toxin that blocks the release of acetylcholine
C. An increase in acetylcholine receptor sites on the motor end plate
D. Addition of a substance that binds to acetylcholine receptor sites

I narrowed the answer choices to A and C and eventually chose A but I wasn't able to decide which one was correct. The correct answer was C. Is option A wrong because blocking cholinesterase would cause buildup of ACh which would eventually cause down-regulation of ACh receptors which would decrease neural transmission?

Thank you in advance
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INSTR_Shinthujah_68
#2 Posted : Wednesday, July 15, 2020 10:29:06 PM
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Hi,

Yes you're correct in the sense that by blocking cholinesterase you will get a buildup of AcH in the junction. With the continued presence of AcH and with it binding to its receptor, the contraction elicited from the first impulse will not end leading to uncontrollable muscle movement. It also means that it WOULD interfere in the repeated transmission of impulses at the NMJ, so A is wrong.

I hope this helps!

-Shin
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