Autonomic Pharmacology USMLE Step 1 Practice Question
A 16-year-old girl develops generalized urticaria, angioedema of the lips, and audible wheezing minutes after ingesting peanuts at a school cafeteria. Vital signs show BP 88/54 mmHg, HR 118/min, RR 22/min, and SpO2 94% on room air. Auscultation reveals diffuse expiratory wheezes bilaterally. She denies prior anaphylaxis or known allergies. Epinephrine 0.3 mg intramuscular is administered immediately into the anterolateral thigh. Serum tryptase level is elevated at 24 ng/mL, confirming mast cell degranulation. Which of the following combinations of receptor effects best explains the life-saving benefits of this drug?
Answer choices
- AAlpha 2 mediated decreased sympathetic outflow and beta 1 blockade
- BDopamine receptor activation in the renal vasculature only
- CBeta 1 blockade and beta 2 blockade
- DMuscarinic blockade and nicotinic stimulation
- EAlpha 1 mediated vasoconstriction and beta 2 mediated bronchodilationCorrect answer
- FAlpha 1 mediated bronchoconstriction and beta 1 mediated increased cardiac contractility
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