All Free Physiology MCQs with Answers

• A. Bronchial asthma
• B. Chronic bronchitis
• C. Scoliosis
• D. Acute bronchitis

Explanation: Scoliosis produces a restrictive ventilatory defect, reducing vital capacity while preserving the FEV₁/FVC percentage.

• A. Anemic Hypoxia
• B. Histotoxic Hypoxia
• C. Stagnant Hypoxia
• D. Hypoxic Hypoxia

Explanation: At high altitude, reduced atmospheric pressure lowers inspired and arterial PO₂, producing hypoxic or hypoxemic hypoxia.

• A. Expiratory reserve volume
• B. Functional residual capacity
• C. Residual volume
• D. Inspiratory reserve volume

Explanation: Functional residual capacity is the volume remaining in the lungs after a normal, quiet expiration.

• A. 125 ml
• B. 500 ml
• C. 1500 ml
• D. 2200 ml

Explanation: Normal adult tidal volume is approximately 500 ml during quiet breathing. It is the amount of air moved in or out with each normal breath.

• A. Carbon monoxide poisoning
• B. Increase in pH of blood
• C. Obstructive pulmonary disease
• D. Decrease in pH of blood

Explanation: Kussmaul breathing is a deep, laboured compensatory response to metabolic acidosis, in which reduced blood pH stimulates ventilation to…

• A. 2% - 3% of total energy spent
• B. 50% -75% of total energy spent
• C. 15% - 20% of total energy spent
• D. 25% - 50% of total energy spent

Explanation: Quiet breathing normally requires only about 2–3% of total body energy expenditure because lung and chest-wall resistance are low.

• A. -2
• B. -5
• C. 0
• D. -7

Explanation: At the start of inspiration, intrapleural pressure is subatmospheric, approximately −2 mmHg in commonly used clinical approximations, and…

• A. Increased pH of blood
• B. Increased oxygen concentration in blood
• C. Remains same
• D. Decreased pH of blood

Explanation: Hypercapnia means excess CO₂, which combines with water to form carbonic acid and increases hydrogen ions, thereby lowering blood pH.

• A. Oxygen dissociation curve shifts to left
• B. Hypoxic hypoxia
• C. Cyanosis
• D. Diffusion capacity of lungs decreases

Explanation: Carbon monoxide occupies haemoglobin binding sites and increases the oxygen affinity of the remaining sites, shifting the oxyhaemoglobin…

• A. Anion balance
• B. Sodium balance
• C. Potassium balance
• D. Ca+2 balance

Explanation: Through pulmonary conversion of angiotensin I to angiotensin II, the lungs influence aldosterone secretion and therefore sodium and water…

• A. Increased lung compliance
• B. Interpleural pressure becomes more negative
• C. The concentration of surfactant is reduced in alveoli
• D. Total chest wall diameter is increased

Explanation: In pneumothorax, pleural pressure approaches atmospheric pressure, so the lung recoils inward while the chest wall recoils outward…

• A. 0.5 L
• B. 2.0 L
• C. 1.1 L
• D. 1.8 L

Explanation: Air remaining after maximal forced expiration is the residual volume, which is approximately 1.1 L in an average woman.

• A. Differential pressure of oxygen in venous blood
• B. Differential pressure of oxygen in arterial blood
• C. Differential pressure of oxygen in in tissue fluids
• D. Differential pressure of oxygen in in hemoglobin synthesis

Explanation: Carotid bodies primarily detect a fall in arterial oxygen partial pressure, especially when PaO₂ falls markedly, and then stimulate…

• A. Partial pressure of CO is less
• B. Bind avidly with Hb
• C. CO is less absorbed in water
• D. Alveolar membrane is less permeable

Explanation: Carbon monoxide binds haemoglobin very avidly, so capillary blood maintains an extremely low dissolved CO partial pressure and continued…

• A. 200 ML
• B. 400 ML
• C. 600 ML
• D. 800 ML

Explanation: Expired air is fully humidified in the airways, causing roughly 400 mL of water loss per day in a resting adult under ordinary conditions.

• A. Increased workload, decreasing duration of exercise
• B. Decreasing workload, increasing duration of exercise
• C. Increased workload, increasing duration of exercise
• D. Decreasing workload, decreasing duration of exercise

Explanation: At high altitude, reduced oxygen availability limits aerobic power, so work capacity is best maintained by lowering the workload and…

• A. is not affected by respiratory
• B. remains constant during exercise
• C. is inversely related to lung compliance
• D. decreased in lying posture

Explanation: When lung compliance is low, greater pressure and muscular effort are needed to produce the same tidal volume, so the elastic work of…

• A. Increased 2,3 BPG
• B. Increased temperature
• C. Increased concentration of carbon - di - oxide
• D. Increased concentration of oxygen

Explanation: Raised 2,3-BPG, temperature and carbon dioxide each reduce haemoglobin's oxygen affinity and shift the dissociation curve to the right.

• A. Increase in respiratory rate
• B. Increase in partial pressure of CO2
• C. Increase in oxygen carrying capacity of blood
• D. Increases in depth of respiration

Explanation: High altitude causes hyperventilation, with increased respiratory rate and depth, and later increases oxygen-carrying capacity through…

• A. It is secreted by Type II pneumocytes
• B. It contains lecithin and sphingomyelin
• C. It increases surface tension
• D. It prevents collapse of smaller alveoli

Explanation: Surfactant is secreted by type II pneumocytes and contains phospholipids including lecithin; it lowers surface tension and prevents small…