USMLE Step 1 · Physiology and Pharmacology

Cardiovascular, Respiratory and Renal Physiology

54 practice questions, each with the answer and an explanation.

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Random questions from this topic, one at a time. You see the answer and the explanation straight after each one.

All 54 questions

  1. Ventricular pressure is rising rapidly while ventricular volume stays constant, just before the aortic valve opens. Which phase of the cardiac cycle is this?
  2. A patient has an end-diastolic volume of 120 mL and an end-systolic volume of 50 mL. What is the ejection fraction?
  3. Which part of the systemic circulation has the greatest total cross-sectional area and therefore the slowest blood velocity?
  4. Which change shifts the oxygen-hemoglobin dissociation curve to the right, so that hemoglobin releases oxygen more easily to the tissues?
  5. A patient has a GFR of 120 mL/min and an effective renal plasma flow of 600 mL/min (from PAH clearance). What is the filtration fraction?
  6. Which segment of the nephron reabsorbs about two thirds of the filtered sodium and water and essentially all of the filtered glucose and amino acids?
  7. Furosemide produces its diuretic effect by blocking which transporter?
  8. A healthy person at sea level breathes room air (FiO2 0.21). The PaCO2 is 40 mmHg, the respiratory quotient is 0.8 and water vapour pressure is 47 mmHg. What is the alveolar PO2?
  9. Which cause of hypoxemia is associated with a normal alveolar-arterial (A-a) oxygen gradient?
  10. A patient with hypoxemia from a large intrapulmonary right-to-left shunt breathes 100% oxygen. What is the expected effect on the PaO2?
  11. Which nerve carries the afferent signal from the baroreceptors of the carotid sinus to the medulla?
  12. Which intervention increases myocardial contractility, shifting the Frank-Starling curve upward rather than moving along it?
  13. A patient has a blood pressure of 160/50 mmHg and bounding pulses with a diastolic decrescendo murmur at the left sternal border. What is the most likely diagnosis?
  14. Which interval on the electrocardiogram mainly reflects the conduction delay in the atrioventricular node?
  15. What produces the plateau (phase 2) of the ventricular myocyte action potential?
  16. Which current is mainly responsible for the spontaneous phase 4 depolarization of the sinoatrial node?
  17. A patient has pH 7.28, HCO3- 12 mEq/L and PaCO2 26 mmHg, with an anion gap of 22. What is the best interpretation?
  18. In a patient with volume depletion, which vessel does angiotensin II constrict preferentially in order to maintain the glomerular filtration rate?
  19. A man produces 8 L of dilute urine a day. The urine osmolality stays low after water deprivation but rises by more than 50% after desmopressin. What is the diagnosis?
  20. Which electrocardiogram change is the earliest sign of hyperkalemia?
  21. Which mechanism best explains the edema in nephrotic syndrome?
  22. Which condition decreases the diffusing capacity of the lung for carbon monoxide (DLCO)?
  23. Which cell type produces pulmonary surfactant?
  24. A person has a tidal volume of 500 mL, an anatomic dead space of 150 mL and a respiratory rate of 12 breaths per minute. What is the alveolar ventilation?
  25. Which change increases the glomerular filtration rate?
  26. A patient's oxygen consumption is 250 mL/min. Arterial oxygen content is 200 mL/L and mixed venous oxygen content is 150 mL/L. What is the cardiac output by the Fick principle?
  27. Which hormone acts on the distal tubule and collecting duct to increase sodium reabsorption and potassium excretion?
  28. A 60-year-old smoker has an FEV1/FVC ratio of 0.55. Which pattern is present?
  29. A man with a plasma creatinine of 2.0 mg/dL has a urinary creatinine of 100 mg/dL and a urine flow of 1 mL/min. What is the approximate GFR?
  30. A 25-year-old runner has a heart rate of 150 beats per minute and a stroke volume of 100 mL. What is the cardiac output?
  31. Which substance is freely filtered and neither reabsorbed nor secreted, making it ideal for measuring GFR?
  32. Which segment of the nephron is impermeable to water and actively reabsorbs sodium chloride in the thick ascending limb?
  33. A diabetic patient has a pH of 7.2, PaCO2 of 25 mm Hg and bicarbonate of 10 mEq/L with an elevated anion gap. What is the diagnosis?
  34. A woman with chronic kidney disease has anemia. Which hormone is deficient?
  35. Which finding is typical of left-sided heart failure?
  36. A patient has pulmonary fibrosis. Which finding is expected on pulmonary function tests?
  37. A patient has a systolic pressure of 120 and a diastolic pressure of 80 mm Hg. What is the approximate mean arterial pressure?
  38. A 68-year-old man has a diastolic murmur heard best at the left sternal border that begins right after S2. Which valve lesion is most likely?
  39. A patient with SIADH is expected to have which laboratory pattern?
  40. A 62-year-old man has a blood pressure of 170/100 mm Hg. A drug that blocks the angiotensin II type 1 receptor is started. Which effect is most expected?
  41. Which hormone is released by atrial myocytes in response to atrial stretch?
  42. A 40-year-old man with polyuria has dilute urine after water deprivation that does not concentrate after desmopressin. What is the diagnosis?
  43. A 55-year-old woman with heart failure has pulmonary edema. Which diuretic acts on the thick ascending limb of the loop of Henle by inhibiting the Na-K-2Cl cotransporter?
  44. In a patient standing up quickly, which reflex raises heart rate and vascular tone?
  45. A man with chronic bronchitis has a PaO2 of 55 mm Hg and a PaCO2 of 60 mm Hg. Which finding is most likely?
  46. A man has a hematocrit of 60 percent. Which change in blood flow is expected?
  47. Which phase of the ventricular action potential is due to calcium influx through L-type channels?
  48. A 70-year-old woman has a crescendo-decrescendo systolic murmur radiating to the carotids and has syncope on exertion. Which valve is affected?
  49. Which lung volume cannot be measured by spirometry alone?
  50. Which vessel type has the largest total cross-sectional area?
  51. A 30-year-old man has a ventricular ejection fraction of 60 percent. His end-diastolic volume is 120 mL. What is his stroke volume?
  52. Which finding is typical of right-sided heart failure?
  53. A 22-year-old woman with a panic attack has rapid breathing, tingling around her mouth and a blood pH of 7.55. What is the acid-base disorder?
  54. Starling forces: which change would cause edema in the legs?

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