Applied and Clinical Physiology Correlations (Pathophysiology Mechanisms) MCQs

Physiology · 61 free questions with answers & explanations.

1. A 68-year-old man with chronic heart failure develops worsening dyspnea. His PCWP is 28 mmHg and cardiac output is 3.1 L/min. The elevated PCWP primarily reflects dysfunction of which Frank-Starling mechanism component?
2. A 55-year-old man with COPD has PaO2 60 mmHg and PaCO2 52 mmHg on ABG. His pulmonary vascular resistance is increased. The primary mechanism driving pulmonary vasoconstriction in this patient is:
3. A 42-year-old woman with nephrotic syndrome is given 40g albumin IV but shows minimal clinical improvement. The most appropriate physiological explanation for the refractoriness to albumin infusion is:
4. During exercise, a healthy 25-year-old's systolic BP rises to 180 mmHg but diastolic remains 80 mmHg. The mechanism responsible for the maintained diastolic pressure despite markedly increased cardiac output is:
5. A 72-year-old with severe aortic stenosis has a transvalvular gradient of 80 mmHg. His left ventricle has undergone concentric hypertrophy. The primary adaptive mechanism allowing maintenance of normal ejection fraction despite increased afterload is:
6. A 58-year-old man with chronic heart failure is started on a loop diuretic. After 2 weeks he develops weakness and his ECG shows flattened T-waves with prominent U-waves. Which physiological mechanism best explains the ECG changes?
7. In a patient with cirrhosis and ascites, the 'forward failure' hypothesis attributes sodium retention to which primary mechanism?
8. Which of the following best explains why a patient with a right-to-left intracardiac shunt does NOT correct their hypoxaemia with 100% inspired oxygen?
9. A mountaineer at 5500 m altitude develops periodic (Cheyne-Stokes) breathing during sleep. The PRIMARY physiological trigger is:
10. In haemorrhagic shock, the transcapillary refill mechanism restores plasma volume by:
11. A 55-year-old man with severe aortic stenosis develops syncope on exertion. The primary hemodynamic mechanism responsible for this symptom is:
12. In a patient with chronic obstructive pulmonary disease developing cor pulmonale, the initial trigger for right ventricular hypertrophy is best explained by:
13. A patient with bilateral renal artery stenosis is placed on an ACE inhibitor. The acute deterioration in renal function occurs because:
14. The Starling forces governing fluid movement across the glomerular capillary differ from those at skeletal muscle capillaries primarily because:
15. During acute hemorrhage, the Bainbridge reflex and Bezold-Jarisch reflex differ in their hemodynamic effects as follows:
16. A 68-year-old patient with severe aortic stenosis undergoes exercise stress testing. During peak exercise, cardiac output fails to increase appropriately. Which physiological mechanism BEST explains the blunted cardiac output response in fixed obstructive valvular disease?
17. In a patient with cor pulmonale secondary to COPD, the central venous pressure is markedly elevated yet cardiac output is low. Which hemodynamic principle explains this dissociation?
18. A mechanically ventilated patient in the ICU develops an abrupt fall in SpO2. The lung compliance curve shows a leftward shift of the pressure-volume loop. Which pathophysiological mechanism accounts for these combined findings?
19. A patient with autoimmune hepatitis develops ascites. Laboratory workup shows serum albumin 2.2 g/dL. Which Starling force alteration predominantly drives hepatic ascites formation in hypoalbuminemia?
20. During hemorrhagic shock, the arterial baroreceptor reflex is activated. Which downstream effector response is the MOST immediate and physiologically prominent in restoring mean arterial pressure?
21. A 55-year-old man with dilated cardiomyopathy has an ejection fraction of 28%. His cardiac output is 3.2 L/min with a heart rate of 90 bpm. His arteriovenous oxygen difference is 7.5 mL/dL. Which of the following compensatory mechanisms is MOST responsible for maintaining tissue oxygenation despite the low cardiac output?
22. A patient with severe aortic stenosis develops syncope on exertion. The pathophysiological mechanism of exertional syncope in this condition is BEST explained by which of the following?
23. A patient with chronic obstructive pulmonary disease and a PaO2 of 52 mmHg receives high-flow oxygen, after which PaCO2 rises from 58 to 72 mmHg. The MOST important physiological mechanism contributing to this CO2 retention is:
24. During a tilt-table test, a patient develops profound hypotension and bradycardia when tilted to 70 degrees upright. Which reflex mechanism is responsible for this vasovagal response?
25. A 28-year-old woman with primary pulmonary hypertension has a mean pulmonary artery pressure of 45 mmHg. If her cardiac output is 4.0 L/min, pulmonary capillary wedge pressure is 8 mmHg, and mean right atrial pressure is 12 mmHg, what is her pulmonary vascular resistance (PVR) in Wood units?
26. A 45-year-old man with untreated essential hypertension (BP 180/110) develops progressive dyspnea on exertion. Echocardiogram shows concentric LV hypertrophy with LV ejection fraction 55%. Which hemodynamic principle best explains why LV hypertrophy developed?
27. In SIADH, the serum sodium is 118 mEq/L. A patient is given hypertonic saline to raise serum Na⁺. The maximum recommended rate of Na⁺ correction is approximately 8–10 mEq/L per 24 hours. Exceeding this rate risks which specific neurological complication?
28. A patient with obstructive sleep apnea (OSA) has repeated nocturnal episodes of hypoxia (SaO2 drops to 75%) and hypercapnia. Which long-term physiological consequence most directly follows from repetitive pulmonary arterial hypoxic vasoconstriction?
29. In hepatic cirrhosis with portal hypertension, patients develop hyperdynamic circulation (high CO, low SVR) and eventually hepatorenal syndrome (HRS). The primary mechanism of renal vasoconstriction in HRS type 1 is:
30. A 50-year-old man with COPD has a PaO2 of 52 mmHg. His peripheral chemoreceptors (carotid bodies) detect this hypoxemia. Which ion channel mechanism in glomus cells initiates the chemoreceptor response?
31. A patient with severe aortic stenosis develops syncope on exertion. Which physiological mechanism best explains this phenomenon?
32. In a patient with massive pulmonary embolism, arterial blood gas shows PaO2 48 mmHg, PaCO2 28 mmHg. The hypoxaemia does NOT correct with 100% oxygen. The predominant mechanism of hypoxaemia is:
33. A patient with chronic liver failure has a low serum albumin and bilateral ankle oedema. The primary Starling force responsible for maintaining plasma oncotic pressure and preventing oedema is:
34. Which cardiovascular reflex is specifically triggered by distension of the pulmonary vasculature and causes reflex bradycardia and hypotension (similar to Bezold-Jarisch reflex)?
35. A 68-year-old man with chronic heart failure has a resting heart rate of 88 bpm and develops Cheyne-Stokes respiration during sleep. The cyclical breathing pattern is primarily due to:
36. A 62-year-old patient with heart failure has a pulmonary capillary wedge pressure (PCWP) of 28 mmHg and a serum albumin of 2.0 g/dL. Which statement correctly applies Starling forces to explain pulmonary edema in this patient?
37. A patient with septic shock develops lactic acidosis with a serum lactate of 8 mmol/L. The primary cause of lactate accumulation in distributive shock is:
38. The Cushing reflex (Cushing response) consists of hypertension, bradycardia, and irregular respiration. Which pathophysiological sequence accurately explains this triad?
39. A patient with SIADH has serum Na+ of 118 mEq/L and urine osmolality of 600 mOsm/kg. Plasma osmolality is 240 mOsm/kg. The MOST appropriate initial management is:
40. A patient with massive pulmonary embolism develops acute right heart failure. Which hemodynamic pattern would be expected on right heart catheterization?
41. During exercise, which of the following mechanisms is primarily responsible for increasing oxygen delivery to working skeletal muscle?
42. A 55-year-old man with known cirrhosis develops refractory ascites. His serum Na is 128 mEq/L, urine osmolality is 600 mOsm/kg, and urine Na is 8 mEq/L. The primary physio-pathological mechanism driving his hyponatraemia is:
43. During a treadmill stress test, a patient's cardiac output increases from 5 L/min to 20 L/min. If mean arterial pressure increases by only 20%, the calculated drop in total peripheral resistance (TPR) is approximately:
44. A patient presents with muscle weakness, ileus, and an ECG showing flat T waves with prominent U waves. Which physiological mechanism best explains the ECG changes in severe hypokalaemia?
45. In a patient with chronic obstructive pulmonary disease who develops acute cor pulmonale, the primary physiological mechanism leading to right ventricular failure is:
46. A patient with type 1 diabetes presents in DKA with pH 7.10, PaCO2 18 mmHg, and HCO3 5 mEq/L. Using Winter's formula, is the respiratory compensation adequate?
47. A patient with nephrotic syndrome has severe hypoalbuminaemia (serum albumin 1.5 g/dL). Despite massive peripheral oedema, she is hypotensive. The physio-pathological explanation is:
48. In a patient with severe aortic stenosis, which haemodynamic findings during cardiac catheterisation best characterise the compensated phase of concentric left ventricular hypertrophy?
49. A patient presents with hypokalaemia, metabolic alkalosis, hypertension, and low plasma renin. Aldosterone is elevated. Which physiological mechanism best explains why primary hyperaldosteronism causes hypokalaemia and metabolic alkalosis?
50. In a patient with acute left ventricular failure, pulmonary oedema develops when pulmonary capillary wedge pressure (PCWP) exceeds which threshold, and what is the primary protective mechanism that delays oedema at moderately elevated pressures?
51. In hepatorenal syndrome type 1 (acute), renal blood flow and GFR fall dramatically despite structurally normal kidneys. Which circulatory mechanism is central to this pathophysiology?
52. A patient with an untreated large arteriovenous fistula (AV fistula) in the thigh develops high-output cardiac failure. The primary physiological reason is:
53. A patient with unilateral renal artery stenosis (URAS) has hypertension. Captopril scintigraphy reveals a delayed and diminished tracer uptake in the affected kidney. The mechanism of hypertension in this condition is:
54. In a patient with severe mitral stenosis, the pulmonary capillary wedge pressure (PCWP) is 28 mmHg. At this pressure, the most likely respiratory finding is:
55. A patient with primary hyperaldosteronism (Conn's syndrome) develops hypokalaemia and metabolic alkalosis. The mechanism of alkalosis is:
56. In a patient with syndrome of inappropriate ADH secretion (SIADH), serum Na+ is 118 mEq/L, serum osmolality is 245 mOsm/kg, urine osmolality is 600 mOsm/kg, and urine Na+ is 65 mEq/L. Why is the urine Na+ elevated despite hyponatraemia?
57. A 45-year-old man presents with perioral numbness, carpopedal spasm, and positive Chvostek sign after thyroid surgery. Serum calcium is 7.2 mg/dL. Which physiological mechanism explains why a reduction in ionised calcium causes increased neuronal excitability?
58. A patient with advanced liver cirrhosis develops renal failure with urine Na < 10 mEq/L, bland urine sediment, and no response to volume loading. Serum creatinine is 3.2 mg/dL. Which physiological mechanism underpins hepatorenal syndrome type 1?
59. A 35-year-old marathon runner collapses at mile 24 with nausea and confusion. Serum Na is 124 mEq/L. She had been drinking large volumes of plain water throughout the race. What physiological failure led to her hyponatremia?
60. Pulmonary oedema develops when pulmonary capillary hydrostatic pressure exceeds the sum of plasma oncotic pressure and lymphatic drainage capacity. At what approximate pulmonary capillary wedge pressure (PCWP) does cardiogenic pulmonary oedema typically begin?
61. Cyanide poisoning blocks Complex IV (cytochrome c oxidase) of the mitochondrial electron transport chain. Which arterial blood gas pattern is expected in a patient with severe cyanide toxicity?