Which of the following structures was most likely the site of action of the botulinum toxin injected into the extrinsic ocular muscles of the 22-year-old man with strabismus?

Correct Answer: B

Rationale: Botulinum toxin primarily acts at somatic nerve terminals by blocking the release of acetylcholine, leading to muscle paralysis. In the context of strabismus treatment, the toxin targets the nerve terminals supplying the extrinsic ocular muscles, specifically affecting neuromuscular transmission at the neuromuscular junction. This action results in localized muscle weakness and temporary paralysis, aiding in the correction of strabismus.

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: D

Rationale: The correct answer is D. Botulinum toxin works by inhibiting the release of acetylcholine from cholinergic terminals, leading to muscle paralysis and relaxation. This action prevents the excessive muscle contractions seen in hemifacial spasms. Inhibition of acetylcholine exocytosis from cholinergic terminals is the mechanism behind the therapeutic effect of botulinum toxin in this case.

Correct Answer: B

Rationale: Baclofen is a muscle relaxant commonly used to treat muscle spasms, making it the most appropriate choice for a patient with muscle spasms. Phenobarbital is an antiseizure medication and would not be indicated for this patient. Tubocurarine and succinylcholine are neuromuscular blocking agents used during surgery, but baclofen would be more appropriate for muscle spasms outside of surgical settings. Chlorpromazine is an antipsychotic medication and would not be indicated for muscle spasms.

Correct Answer: A

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.