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Physiology Flashcards

6 cards from real USMLE 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. Which phase of the cardiac action potential in ventricular cardiomyocytes is responsible for the prolonged plateau and is mediated by L-type calcium channels?

    Answer: Phase 2 (plateau phase)

    Phase 2 of the ventricular action potential is the plateau phase maintained by calcium influx through L-type (long-lasting) calcium channels, balanced by potassium efflux.

  2. A patient with primary hyperaldosteronism (Conn syndrome) will have which electrolyte abnormality?

    Answer: Hypokalemia and hypertension

    Excess aldosterone promotes sodium retention and potassium excretion in the collecting duct, causing hypertension (volume expansion) and hypokalemia.

  3. Which pulmonary function test finding is characteristic of obstructive lung disease?

    Answer: Decreased FEV1/FVC ratio (<0.70)

    Obstructive diseases (asthma, COPD, emphysema) show decreased FEV1/FVC ratio (<0.70) because airflow obstruction disproportionately reduces FEV1 more than FVC.

  4. The juxtaglomerular apparatus (JGA) releases renin in response to which stimulus?

    Answer: Decreased renal perfusion pressure

    JGA granular cells release renin in response to decreased renal perfusion pressure (baroreceptor mechanism), decreased NaCl at the macula densa, and sympathetic stimulation (beta-1 receptors).

  5. A patient has a positive D-dimer test and imaging confirms pulmonary embolism. Which ventilation-perfusion change occurs in the affected lung segment?

    Answer: Increased V/Q ratio (dead space physiology)

    PE blocks perfusion to a ventilated lung segment, increasing V/Q ratio toward infinity (dead space effect), wasting ventilation without gas exchange.

  6. Insulin promotes glucose uptake in muscle and adipose tissue by stimulating translocation of which glucose transporter?

    Answer: GLUT4

    Insulin stimulates translocation of GLUT4-containing vesicles to the plasma membrane in muscle and adipose tissue, increasing glucose uptake via PI3K-Akt signaling.