Skeletal Muscle Paralysis

[OurTown]

Is this answer correct? I have been using an online question bank for prep but there seems to be a number of incorrect answers:






Q. Acetylcholine is a neurotransmitter that is responsible for initiating skeletal muscle contractions. Which of the following drugs might cause skeletal muscle paralysis?

1. A drug that interferes with acetylcholine breakdown in the synapse.
2. A drug that causes sodium channels to open in the neurons serving the skeletal muscles.
3. A drug that prevents release of acetylcholine to the synapse.
4. Any of the above could cause paralysis.

Solution:The correct answer is 3
If acetylcholine is the neurotransmitter used to initiate skeletal muscle contraction, it would need to be released to the synapse to exert its effects. If it were not present in the synapse, no muscle contraction should occur. If a drug were to prevent the release of acetylcholine, paralysis should occur in the muscle.


I answered 4-Any of the above cause skeletal muscle paralysis, but the bank marked it wrong. Acetylcholinesterase inhibitors like sarin gas (which would be one example of answer 1) cause spastic paralysis, right? And there are examples of 2 causing paralysis as well.

Am I defining paralysis too broadly or is this test bank's answer bogus?

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[theCLE]

I believe "paralysis" means not being able to move the muscle, which would only be #4. On the other hand, muscle tetanus (spasm and strong lingering contraction of the muscle) would happen with the first two: having too much ach or opening the NA channels to allow muscles to contract. I hope this helps.

 

[MedPR]

Is this answer correct? I have been using an online question bank for prep but there seems to be a number of incorrect answers:







Q. Acetylcholine is a neurotransmitter that is responsible for initiating skeletal muscle contractions. Which of the following drugs might cause skeletal muscle paralysis?

1. A drug that interferes with acetylcholine breakdown in the synapse.
2. A drug that causes sodium channels to open in the neurons serving the skeletal muscles.
3. A drug that prevents release of acetylcholine to the synapse.
4. Any of the above could cause paralysis.

Solution:The correct answer is 3
If acetylcholine is the neurotransmitter used to initiate skeletal muscle contraction, it would need to be released to the synapse to exert its effects. If it were not present in the synapse, no muscle contraction should occur. If a drug were to prevent the release of acetylcholine, paralysis should occur in the muscle.


I answered 4-Any of the above cause skeletal muscle paralysis, but the bank marked it wrong. Acetylcholinesterase inhibitors like sarin gas (which would be one example of answer 1) cause spastic paralysis, right? And there are examples of 2 causing paralysis as well.

Am I defining paralysis too broadly or is this test bank's answer bogus?

1 = no breakdown of Ach = neverending contraction
2 = constant depol = neverending contraction

 

[neurodoc]

I answered 4-Any of the above cause skeletal muscle paralysis, but the bank marked it wrong. Acetylcholinesterase inhibitors like sarin gas (which would be one example of answer 1) cause spastic paralysis, right? And there are examples of 2 causing paralysis as well.

Am I defining paralysis too broadly or is this test bank's answer bogus?

By "paralysis" they are talking about a failure of muscle contraction under ordinary normal motor neuron stimulus. In general, "paralysis" refers to muscle "weakness." There are two types, "spastic" and "flaccid." Blockade of the nicotinic cholinergic motor end plates leads to flaccid paralysis. Spastic paralysis can be due to ACh-ase inhibitors like the Sarin "nerve gas." In that case the muscles are overstimulated by ACh, leading to spasms/muscle contractions. The "antidote" is an atropine-like anticholinergic.