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Question 1. Which of the following best describes the primary source of ATP during sustained moderate‑intensity exercise? A) Glycolysis B) Oxidative phosphorylation of fatty acids C) Creatine phosphate breakdown D) Lactic acid fermentation Answer: B Explanation: During prolonged moderate‑intensity activity, muscle cells rely mainly on oxidative phosphorylation of fatty acids because it yields the most ATP per molecule and can be maintained for many hours. Question 2. The sodium‑potassium ATPase pump moves which ions and in what ratio per ATP hydrolyzed? A) 3 Na⁺ out, 2 K⁺ in B) 2 Na⁺ out, 3 K⁺ in C) 3 Na⁺ in, 2 K⁺ out D) 2 Na⁺ in, 3 K⁺ out Answer: A Explanation: The Na⁺/K⁺‑ATPase extrudes three sodium ions and imports two potassium ions for each ATP molecule hydrolyzed, establishing the resting membrane potential. Question 3. Failure of the Na⁺/K⁺ pump in neuronal cells most directly leads to which of the following cellular changes? A) Decreased intracellular calcium B) Cell shrinkage due to water loss C) Membrane depolarization and cellular swelling D) Increased mitochondrial ATP production
Answer: C Explanation: Pump failure prevents extrusion of Na⁺, causing intracellular Na⁺ accumulation, water influx, swelling, and loss of the negative resting membrane potential (depolarization). Question 4. Which adaptive response is most likely to occur in the myocardium of a patient with chronic hypertension? A) Atrophy B) Hypertrophy C) Metaplasia D) Dysplasia Answer: B Explanation: Chronic pressure overload stimulates cardiomyocyte hypertrophy (increase in cell size) to generate greater contractile force, a classic example of physiological adaptation. Question 5. Which of the following mechanisms is primarily responsible for cellular injury during ischemia‑reperfusion? A) Accumulation of lactic acid only B) Generation of reactive oxygen species (ROS) C) Direct DNA fragmentation by ATP depletion D) Excessive protein synthesis Answer: B Explanation: Reintroduction of oxygen after ischemia leads to massive ROS production, causing lipid peroxidation, protein oxidation, and DNA damage, which are central to reperfusion injury. Question 6. Apoptosis differs from necrosis in that apoptosis: A) Causes inflammation due to cell lysis
Question 9. A patient with chronic obstructive pulmonary disease (COPD) has a V/Q ratio of 0.5 in a lung region. This indicates: A) Normal ventilation and perfusion B) High ventilation relative to perfusion (dead space) C) Low ventilation relative to perfusion (shunt‑like) D) No gas exchange abnormality Answer: C Explanation: A V/Q ratio <1 signifies ventilation is insufficient for the amount of perfusion, leading to hypoxemia similar to a shunt. Question 10. Which of the following best describes the primary physiologic difference between restrictive and obstructive lung diseases? A) Restrictive diseases have increased airway resistance; obstructive diseases have reduced lung compliance. B) Restrictive diseases reduce total lung capacity; obstructive diseases increase residual volume. C) Restrictive diseases increase diffusion capacity; obstructive diseases decrease it. D) Restrictive diseases cause hyperinflation; obstructive diseases cause atelectasis. Answer: B Explanation: Restrictive disorders limit lung expansion, lowering total lung capacity, whereas obstructive disorders impede airflow, increasing residual volume and functional residual capacity. Question 11. In acute respiratory distress syndrome (ARDS), the primary cause of hypoxemia is: A) Decreased atmospheric oxygen pressure B) V/Q mismatch due to alveolar collapse and flooding C) Increased hemoglobin affinity for oxygen D) Hyperventilation leading to respiratory alkalosis
Answer: B Explanation: ARDS leads to alveolar edema and collapse, producing extensive V/Q mismatch and shunting, which markedly reduces arterial oxygenation. Question 12. The SA node initiates the cardiac impulse at an intrinsic rate of approximately: A) 40 beats/min B) 60–100 beats/min C) 120–150 beats/min D) 180–200 beats/min Answer: B Explanation: The sinoatrial node normally fires at 60‑100 impulses per minute, setting the heart’s basal rhythm. Question 13. Which of the following factors most directly increases preload? A) Increased systemic vascular resistance B) Decreased venous return C) Increased end‑diastolic volume D) Decreased myocardial contractility Answer: C Explanation: Preload is the ventricular wall stress at end‑diastole, primarily determined by end‑diastolic volume (the amount of blood filling the ventricle). Question 14. In distributive (septic) shock, the predominant hemodynamic change is: A) Decreased cardiac output due to myocardial depression B) Increased systemic vascular resistance C) Decreased systemic vascular resistance leading to warm extremities
C) Swelling of organelles and plasma membrane rupture D) Autophagic vacuole formation without inflammation Answer: C Explanation: Necrosis is characterized by cellular swelling, loss of membrane integrity, and subsequent inflammation due to release of intracellular contents. Question 18. During hypoxia, cells primarily increase glycolysis to compensate for reduced oxidative phosphorylation. This shift leads to accumulation of: A) Acetyl‑CoA B) Lactic acid C) Ketone bodies D) Urea Answer: B Explanation: Anaerobic glycolysis converts pyruvate to lactate, raising intracellular and plasma lactate levels during hypoxic conditions. Question 19. Which of the following statements about free radicals is FALSE? A) They can initiate lipid peroxidation of cellular membranes. B) Antioxidants such as glutathione neutralize them. C) They are always produced exogenously from environmental toxins. D) Excessive free radicals contribute to DNA damage. Answer: C Explanation: Free radicals are generated both endogenously (mitochondrial respiration, enzymatic reactions) and exogenously; they are not exclusively external. Question 20. In the context of the cardiac cycle, the “isovolumetric contraction” phase occurs:
A) After the aortic valve opens B) While all valves are closed and ventricular pressure rises C) When the mitral valve is open and blood fills the ventricle D) During diastole when the ventricles relax Answer: B Explanation: Isovolumetric contraction is the brief interval after the AV valves close and before the semilunar valves open, during which ventricular pressure increases without volume change. Question 21. Which of the following best explains the mechanism of pulmonary edema in left‑sided heart failure? A) Increased capillary permeability due to infection B) Elevated left atrial pressure transmitting backward to pulmonary veins and capillaries C) Decreased oncotic pressure from hypoalbuminemia D) Direct injury to alveolar epithelium by toxins Answer: B Explanation: Left‑sided failure raises left atrial and pulmonary venous pressures, leading to transudation of fluid into the interstitium and alveoli. Question 22. A 45‑year‑old man presents with a “pulsus paradoxus.” Which condition is most likely responsible? A) Aortic stenosis B) Cardiac tamponade C) Mitral valve prolapse D) Hypertrophic cardiomyopathy Answer: B
C) Blood flow velocity in pulmonary arteries D) Airway resistance Answer: B Explanation: Oxygen diffusion follows its partial pressure gradient; the higher alveolar PO₂ relative to capillary PO₂ drives O₂ into blood. Question 26. A patient with severe anemia shows a normal arterial PO₂ but low arterial O₂ content. This finding is explained by: A) Decreased hemoglobin concentration reducing O₂ carrying capacity B) Impaired diffusion of O₂ across the alveolar membrane C) Increased shunting of blood past ventilated alveoli D) Hyperventilation causing hypocapnia Answer: A Explanation: Arterial PO₂ reflects dissolved O₂, which remains normal; however, reduced hemoglobin lowers total O₂ content despite normal PO₂. Question 27. Which of the following best describes the effect of increased afterload on left ventricular ejection fraction (LVEF)? A) LVEF increases because the ventricle contracts more forcefully. B) LVEF decreases due to higher resistance against which the ventricle must pump. C) LVEF is unchanged; afterload only affects heart rate. D) LVEF becomes unpredictable and varies randomly. Answer: B Explanation: Afterload is the pressure the ventricle must overcome; increased afterload reduces stroke volume and thus LVEF.
Question 28. In the setting of acute myocardial infarction, which cellular process is most directly responsible for the loss of contractile function? A) Increased ATP production by mitochondria B) Calcium overload leading to hypercontraction and necrosis C) Up‑regulation of β‑adrenergic receptors D) Enhanced glycolysis providing excess energy Answer: B Explanation: Ischemia causes ATP depletion, failure of calcium pumps, intracellular calcium overload, hypercontraction, and subsequent necrotic cell death. Question 29. Which of the following best explains why hyperventilation leads to respiratory alkalosis? A) Increased CO₂ elimination raises arterial CO₂ levels. B) Decreased CO₂ elimination lowers arterial CO₂, raising pH. C) Hyperventilation increases O₂ uptake, which directly raises pH. D) It causes a shift of the bicarbonate buffer toward CO₂ production. Answer: B Explanation: Hyperventilation blows off CO₂, decreasing PaCO₂, which reduces carbonic acid concentration and raises blood pH (alkalosis). Question 30. A 60‑year‑old smoker has a reduced diffusing capacity (DLCO). Which pathophysiologic change most likely accounts for this finding? A) Increased alveolar surface area B) Thickened alveolar‑capillary membrane from emphysema C) Decreased hemoglobin affinity for O₂ D) Elevated cardiac output
B) High altitude exposure C) Anemia D) Carbon monoxide poisoning Answer: A Explanation: A pulmonary embolus blocks perfusion to ventilated alveoli, creating a V/Q mismatch and resulting hypoxemia. Question 34. The primary mechanism by which carbon monoxide (CO) causes tissue hypoxia is: A. Decreasing atmospheric oxygen partial pressure B. Binding to hemoglobin with a higher affinity than O₂, reducing O₂ delivery C. Directly destroying alveolar capillary membranes D. Increasing metabolic demand of cells Answer: B Explanation: CO binds to the same site on hemoglobin as O₂ but with ~250‑times greater affinity, forming carboxyhemoglobin and preventing O₂ transport. Question 35. Which of the following best characterizes the hemodynamic changes in early (compensated) hypovolemic shock? A) Decreased systemic vascular resistance and increased cardiac output B) Increased heart rate, increased systemic vascular resistance, and maintained blood pressure C) Decreased heart rate and decreased preload only D) Increased cardiac output with reduced afterload Answer: B Explanation: Early hypovolemic shock triggers sympathetic activation: tachycardia, vasoconstriction (↑SVR), and mechanisms to preserve MAP despite reduced volume.
Question 36. In the setting of severe hypercapnia, the primary driver of the respiratory center’s increased ventilation is: A) Low arterial pH (acidosis) detected by central chemoreceptors B) High arterial pH detected by peripheral chemoreceptors C) Decreased oxygen saturation sensed by carotid bodies D) Increased blood glucose levels Answer: A Explanation: Central chemoreceptors in the medulla respond to elevated PaCO₂ (which diffuses into CSF, forming carbonic acid) by stimulating ventilation to blow off CO₂. Question 37. Which of the following best explains the phenomenon of “shunting” in the lung? A) Air moving from low‑pressure alveoli to high‑pressure alveoli B) Blood flowing through alveoli that are not ventilated, resulting in no gas exchange C) Increased diffusion of gases across the alveolar membrane D) Redistribution of blood from peripheral to central circulation Answer: B Explanation: A physiologic shunt occurs when perfusion passes through non‑ventilated (or poorly ventilated) alveoli, leading to arterial hypoxemia unresponsive to O₂ therapy. Question 38. Which type of cellular adaptation is most likely to occur in the urothelium of a patient with chronic bladder outlet obstruction? A) Atrophy B) Hypertrophy C) Metaplasia D) Dysplasia Answer: C
C) High serum lactate reflecting tissue hypoperfusion D) Decreased serum cortisol Answer: C Explanation: Septic shock leads to cellular hypoxia despite normal or high cardiac output, causing anaerobic metabolism and elevated lactate levels. Question 42. Which of the following best explains why the right ventricle is more susceptible to failure in massive pulmonary embolism? A) It operates at lower pressures under normal conditions and cannot generate high pressures against an obstructed pulmonary arterial tree. B) It has a thicker myocardium than the left ventricle, making it more prone to ischemia. C) It receives blood from the systemic circulation, which is already compromised. D) It is supplied primarily by the coronary artery, which is occluded in embolism. Answer: A Explanation: The right ventricle normally pumps against a low‑pressure pulmonary circuit; a sudden increase in pulmonary vascular resistance overwhelms its ability to maintain output. Question 43. Which of the following is the most common cause of metabolic acidosis in patients with severe COPD exacerbation? A) Retention of CO₂ leading to respiratory acidosis only B) Accumulation of lactic acid due to tissue hypoxia C) Excessive vomiting causing loss of HCl D) Administration of bicarbonate therapy Answer: B Explanation: In severe COPD, hypoxemia can cause tissue hypoxia, leading to anaerobic glycolysis and lactic acid buildup, contributing to metabolic acidosis.
Question 44. Which of the following best describes the role of 2,3‑BPG in oxygen transport? A) Increases hemoglobin affinity for O₂, facilitating loading in the lungs. B) Decreases hemoglobin affinity for O₂, facilitating unloading in peripheral tissues. C) Acts as a co‑factor for carbonic anhydrase in red blood cells. D) Directly binds to O₂ and transports it to tissues. Answer: B Explanation: 2,3‑BPG binds to the β‑chains of deoxy‑hemoglobin, stabilizing the T‑state and lowering O₂ affinity, thus promoting oxygen release in tissues. Question 45. Which of the following statements about the alveolar‑arterial (A‑a) gradient is true? A) It remains constant regardless of age or FiO₂. B) A widened A‑a gradient indicates a problem with diffusion, V/Q mismatch, or shunt. C) A normal A‑a gradient rules out any pulmonary pathology. D) It is calculated by subtracting PaCO₂ from alveolar PO₂. Answer: B Explanation: An increased A‑a gradient suggests impaired gas exchange due to diffusion limitation, V/Q mismatch, or shunt; it varies with age and FiO₂. Question 46. In the event of a large myocardial infarction, which of the following changes in the ECG is most characteristic? A) Diffuse ST‑segment elevation across all leads B) ST‑segment depression in leads V1‑V C) ST‑segment elevation localized to leads corresponding to the infarcted region D) Tall, peaked T waves in all leads Answer: C
C) Widened P wave D) ST‑segment depression Answer: B Explanation: Elevated extracellular K⁺ accelerates repolarization, producing characteristic tall, peaked T waves on the ECG. Question 50. Which of the following best describes the “Starling curve” for the heart? A) Relationship between heart rate and contractility B) Relationship between preload (end‑diastolic volume) and stroke volume C) Relationship between afterload and ejection fraction D) Relationship between systemic vascular resistance and cardiac output Answer: B Explanation: The Starling relationship demonstrates that, up to a point, increased preload leads to increased stroke volume due to optimal sarcomere length. Question 51. Which of the following best explains the mechanism of action of loop diuretics in treating pulmonary edema? A) Inhibit Na⁺/K⁺‑ATPase in the distal tubule B) Block Na⁺‑K⁺‑2Cl⁻ cotransporter in the thick ascending limb, promoting natriuresis and diuresis C) Increase aldosterone secretion leading to fluid excretion D) Enhance reabsorption of water in the collecting duct Answer: B Explanation: Loop diuretics inhibit the Na⁺‑K⁺‑2Cl⁻ transporter in the Henle’s loop, causing marked natriuresis and diuresis, reducing intravascular volume and pulmonary capillary pressure.
Question 52. Which of the following best characterizes the effect of increased intrathoracic pressure on venous return? A) Increases venous return by compressing the heart B) Decreases venous return because elevated pressure impedes flow into the right atrium C) Has no effect on venous return D) Increases afterload on the left ventricle only Answer: B Explanation: Elevated intrathoracic pressure reduces the pressure gradient between peripheral veins and the right atrium, thereby diminishing venous return. Question 53. In a patient with obstructive sleep apnea, the most common nocturnal arterial blood gas abnormality is: A) Hypercapnia due to hypoventilation B) Severe metabolic alkalosis C) Hypoxemia with normal CO₂ D) Respiratory alkalosis from hyperventilation Answer: A Explanation: Apneic episodes cause intermittent hypoventilation, leading to CO₂ retention (hypercapnia) and consequent hypoxemia. Question 54. Which of the following best explains the term “capillary leak syndrome” in severe sepsis? A) Increased hydrostatic pressure causing fluid transudation B) Loss of endothelial integrity allowing plasma proteins and fluid to escape into interstitium C) Decreased cardiac output leading to tissue edema D) Overproduction of urine by the kidneys
