All Free Physiology MCQs with Answers

• A. Haldane effect
• B. Hamburger effect
• C. Breur effect
• D. Bohr effect

Explanation: The Bohr effect describes reduced haemoglobin affinity for oxygen when tissue CO2 and hydrogen ion concentration rise, promoting oxygen…

• A. Apex of lung
• B. Base of lung
• C. Posterior lobe of lung
• D. Middle lobe of lung

Explanation: The apex has relatively greater ventilation-perfusion ratio because perfusion decreases more sharply than ventilation toward the top of…

• A. Tidal volume
• B. Inspiratory reserve volume plus expiratory volume
• C. Tidal volume plus inspiratory reserve volume plus expiratory reserve volume
• D. Expiratory reserve volume plus reserve volume

Explanation: Vital capacity is the maximum volume expired after a maximal inspiration, so it equals tidal volume plus inspiratory reserve volume plus…

• A. Increased pH
• B. Hypothermia
• C. HbF
• D. Hypoxia

Explanation: Hypoxia decreases haemoglobin's oxygen affinity mainly through increased 2,3-BPG, shifting the dissociation curve to the right.

• A. Hypoxia
• B. Alkalosis
• C. Increased HbF
• D. Hypothermia

Explanation: Alkalosis, hypothermia and HbF increase haemoglobin's oxygen affinity by shifting the dissociation curve to the left.

• A. Dopamine metabolism
• B. Serotonin metabolism
• C. Adrenaline metabolism
• D. PGE2 production

Explanation: Pulmonary endothelial cells metabolise circulating serotonin, making serotonin clearance a recognised non-respiratory function of the…

• A. Ciliary motility
• B. Cellular hyperplasia
• C. Mucous secretion
• D. All of the above

Explanation: Smoking impairs ciliary movement and causes mucous gland or epithelial hyperplasia with increased mucus secretion.

• A. Herring - Breur reflex
• B. Bainbridge reflex
• C. Autonomic reflex
• D. Dynamic stretch reflex

Explanation: The Hering-Breuer inflation reflex is triggered by vagal stretch receptors during lung inflation and limits further inspiration.

• A. The relative proportion of reduced and oxygenated hemoglobin
• B. The absolute amount of reduced hemoglobin
• C. Thickness of the skin
• D. Fragility of capillaries

Explanation: Cyanosis becomes clinically apparent when the absolute amount of reduced haemoglobin rises to roughly 5 g/dL, rather than simply from a…

• A. Intrapulmonary pressure falls
• B. Intra thoracic pressure rises
• C. Intra-abdominal pressure rises
• D. The partial pressure of O2 in dead space rises

Explanation: During inspiration, intrapulmonary and intrathoracic pressures fall, while descent of the diaphragm raises intra-abdominal pressure.

• A. Decrease in arterial carbon dioxide level
• B. None of the above
• C. Increase in arterial oxygen level
• D. Increase in arterial carbon dioxide level

Explanation: An increase in arterial CO₂ raises hydrogen ion concentration in brain extracellular fluid and strongly stimulates the medullary…

• A. Rise in pH
• B. Rise in carbon dioxide tension
• C. Rise in temperature
• D. Rise in H+ ion

Explanation: A rise in temperature, CO₂, or H⁺ shifts the curve rightward and promotes oxygen unloading.

• A. Cyanosis
• B. Hypercapnia
• C. Dyspnea
• D. Hypoxia

Explanation: Hypoventilation reduces CO₂ elimination, so arterial CO₂ rises and hypercapnia is the defining biochemical abnormality.

• A. Positive
• B. Less negative
• C. More negative
• D. Equal to the intra alveolar pressure

Explanation: Diaphragmatic contraction enlarges the thoracic cavity and makes intrapleural pressure more negative.

• A. Bicarbonate
• B. Carbomino compounds
• C. Dissolved
• D. CO

Explanation: Most carbon dioxide is converted inside red blood cells to bicarbonate, which then circulates in the plasma; only a smaller fraction is…

• A. Cerebrum
• B. Medulla oblongata
• C. Hypothalamus
• D. Cerebellum

Explanation: The medulla contains the essential respiratory rhythm-generating centres, so its destruction stops the automatic drive to breathe.

• A. Midbrain
• B. Spinal cord
• C. Medulla oblongata
• D. HypothalamusTry Nootropic Supplements

Explanation: The medulla contains the main dorsal and ventral respiratory groups that generate and regulate the basic breathing rhythm.