Practice sessionHEALTHCARE & MEDICAL EXAMSMEDICAL LICENSING

USMLE (United States Medical Licensing Examination) Practice Exam 09

Practice exam for USMLE (United States Medical Licensing Examination).

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Question 1 of 1000%

Time remaining180:00

Attempts allowedUnlimited

Difficulty mixE • M • H

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Question 1

MEDIUM

180:00

A 62-year-old man with long-standing hypertension is started on a medication that lowers blood pressure by increasing intracellular cGMP in vascular smooth muscle. Which of the following best describes the immediate molecular effect responsible for this drug’s vasodilatory action?

cGMP (eg, via nitric oxide signaling) activates protein kinase G, which decreases intracellular Ca2+ and promotes activation of myosin light-chain phosphatase, leading to dephosphorylation of myosin light chains and relaxation. Increased L-type Ca2+ influx and increased MLCK activity would promote contraction, not relaxation.

Select one answer

Activation of myosin light-chain phosphatase leading to dephosphorylation of myosin light chains

Increased calcium influx through L-type calcium channels in vascular smooth muscle

Inhibition of adenylate cyclase resulting in decreased cAMP

Opening of ATP-sensitive potassium channels causing membrane depolarization

Phosphorylation of myosin light chains via increased myosin light-chain kinase activity

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USMLE (United States Medical Licensing Examination) Practice Exam 09

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