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16 multiple-choice questions and 14 flashcards on Cardiovascular System, about 9% of the USMLE Step 1 bank. Every one carries a written rationale.
Cardiovascular System is one of 10 chapters in CoStudy's USMLE Step 1 — Medical Licensing bank, and it holds 16 of the bank's 172 multiple-choice questions — roughly 9% of the total. That proportion is not arbitrary: chapters follow the certifying body's published exam outline, and the number of questions in each is set by that domain's published weight, so the share of your practice time this chapter takes matches the share of the real exam it accounts for.
Studying by chapter is worth doing once you have a diagnostic score. A single overall percentage tells you whether you are close; it does not tell you which domain is dragging. Working a weak chapter in isolation, and re-testing it in isolation, is the fastest way to move a score that has stalled — and it is why the mock exams in CoStudy report by domain rather than as one number.
1 questions drawn from this chapter, with the full rationale shown — the controlling principle behind the right answer, and why each wrong option tempts and fails.
On the cardiac action potential of a ventricular myocyte, what causes the plateau (phase 2)?
Answer: C — Balanced calcium influx and potassium efflux
Phase 2 plateau results from a balance between inward Ca²⁺ current through L-type channels and outward K⁺ current. This sustained depolarization is what couples electrical activity to contraction (Ca²⁺-induced Ca²⁺ release from the SR).
4 cards from the 14 in this chapter.
S1 vs S2 heart sounds?
S1: closure of mitral/tricuspid (start of systole). S2: closure of aortic/pulmonary.
Frank-Starling law?
Increased preload → increased stroke volume (within physiologic limits).
S4 gallop?
Heard late diastole. Stiff ventricle (HTN, aortic stenosis, hypertrophy).
Calcium channel blockers?
Dihydropyridines (amlodipine — vasodilation), non-DHP (verapamil, diltiazem — heart rate).
These are a sample. The full Cardiovascular System chapter runs 30 items with per-chapter progress tracking, on the web and in the iOS app.
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