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Comprehensive Basic Science Flashcards

7 cards from real NBME practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. A 55-year-old man develops digitalis toxicity. Which electrolyte abnormality most potentiates this toxicity?

    Answer: Hypokalemia

    Hypokalemia potentiates digoxin toxicity because K+ and digoxin compete for the same binding site on the Na+/K+-ATPase.

  2. The Frank-Starling mechanism states that increased ventricular end-diastolic volume leads to which of the following?

    Answer: Increased stroke volume

    Greater sarcomere stretch from increased preload optimizes actin-myosin overlap, increasing the force of contraction and stroke volume.

  3. A patient with renal artery stenosis has elevated renin. Which of the following is the direct product of renin's enzymatic action?

    Answer: Angiotensin I

    Renin cleaves angiotensinogen to angiotensin I, which is then converted to angiotensin II by ACE in the lungs.

  4. A drug inhibits cyclooxygenase irreversibly. Which cell type is most functionally impaired because it cannot synthesize new enzyme?

    Answer: Platelets

    Platelets are anucleate and cannot synthesize new COX; aspirin's irreversible inhibition affects them for their entire 10-day lifespan.

  5. During a Valsalva maneuver, which phase is associated with a transient increase in venous return and cardiac output upon release?

    Answer: Phase IV (post-release overshoot)

    Phase IV shows reflex bradycardia and BP overshoot as thoracic venous blood surges back to the heart after intra-thoracic pressure normalizes.

  6. A patient taking a loop diuretic develops metabolic alkalosis. Which mechanism best explains this?

    Answer: Contraction alkalosis and increased aldosterone-mediated H+ secretion

    Volume depletion concentrates bicarbonate (contraction alkalosis) and stimulates aldosterone, increasing collecting duct H+ secretion.

  7. A newborn is found to have a patent ductus arteriosus. Which auscultatory finding is most characteristic?

    Answer: Continuous machine-like murmur at the left infraclavicular area

    The PDA allows continuous left-to-right shunting throughout systole and diastole, producing a machinery murmur heard best below the left clavicle.