Mechanism of breathing MCQs With Answer

by

Mechanism of breathing MCQs With Answer – This concise, Student-friendly post covers the core principles of pulmonary ventilation, pressure gradients, lung compliance, surfactant action, respiratory muscles and neural control tailored for B. Pharm students. It emphasizes clinical relevance, pharmacological implications and physiological concepts such as alveolar and intrapleural pressures, airway resistance, and gas exchange. Ideal for exam preparation and rapid revision, these targeted MCQs strengthen understanding of respiratory mechanics and highlight areas where drugs may influence breathing. Clear explanations and focused questions improve retention and application in pharmacy practice. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which law best explains the inverse relationship between pressure and volume during pulmonary ventilation?

  • Henry’s law
  • Poiseuille’s law
  • Boyle’s law
  • Charles’s law

Correct Answer: Boyle’s law

Q2. During quiet inspiration, the primary muscle responsible for increasing thoracic volume is the:

  • External intercostals
  • Diaphragm
  • Sternocleidomastoid
  • Internal intercostals

Correct Answer: Diaphragm

Q3. At the end of a normal relaxed expiration (functional residual capacity), intrapleural pressure is typically:

  • Greater than atmospheric pressure
  • Equal to atmospheric pressure
  • Negative relative to atmospheric pressure
  • Zero absolute pressure

Correct Answer: Negative relative to atmospheric pressure

Q4. Surfactant reduces surface tension in alveoli primarily by:

  • Increasing alveolar elastic recoil
  • Decreasing alveolar surface area
  • Lowering surface tension at the air–liquid interface
  • Preventing capillary leakage

Correct Answer: Lowering surface tension at the air–liquid interface

Q5. Lung compliance is defined as the change in lung volume per unit change in:

  • Airway resistance
  • Transpulmonary pressure
  • Arterial oxygen tension
  • Minute ventilation

Correct Answer: Transpulmonary pressure

Q6. Airflow resistance is most influenced by which factor in the airways?

  • Length of the airway
  • Viscosity of inspired air
  • Radius of the airway
  • Alveolar size

Correct Answer: Radius of the airway

Q7. Which pressure must be lower than alveolar pressure to allow airflow into the lungs?

  • Atmospheric pressure
  • Intrapleural pressure
  • Pulmonary venous pressure
  • Transmural pressure of bronchi

Correct Answer: Atmospheric pressure

Q8. The primary neural control center for rhythmic breathing is located in the:

  • Hypothalamus
  • Pons and medulla oblongata
  • Thalamus
  • Basal ganglia

Correct Answer: Pons and medulla oblongata

Q9. Peripheral chemoreceptors that respond to hypoxemia are located in the:

  • Medulla oblongata
  • Carotid and aortic bodies
  • Pulmonary alveoli
  • Bronchial mucosa

Correct Answer: Carotid and aortic bodies

Q10. An increase in alveolar CO2 (hypercapnia) primarily stimulates ventilation by acting on:

  • Peripheral chemoreceptors only
  • Central chemoreceptors in the medulla
  • The neuromuscular junction
  • Mechanical stretch receptors in the lungs

Correct Answer: Central chemoreceptors in the medulla

Q11. Tidal volume refers to:

  • The maximum air expelled after maximal inspiration
  • Air remaining after maximal expiration
  • Volume of air inspired or expired in a normal breath
  • Sum of residual and expiratory reserve volumes

Correct Answer: Volume of air inspired or expired in a normal breath

Q12. Minute ventilation equals tidal volume multiplied by:

  • Residual volume
  • Respiratory rate
  • Dead space volume
  • Functional residual capacity

Correct Answer: Respiratory rate

Q13. Anatomical dead space is best described as:

  • Alveoli not perfused with blood
  • Conducting airways where no gas exchange occurs
  • Collapsed alveoli after expiration
  • Area of shunt physiology

Correct Answer: Conducting airways where no gas exchange occurs

Q14. Which statement about pneumothorax is correct regarding pleural pressure?

  • Pleural pressure becomes more negative
  • Pleural pressure equals atmospheric pressure
  • Alveolar pressure falls below pleural pressure
  • Pleural pressure becomes extremely positive

Correct Answer: Pleural pressure equals atmospheric pressure

Q15. The major effect of bronchodilators (e.g., beta-2 agonists) on airflow is to:

  • Increase airway resistance
  • Decrease airway radius
  • Increase airway radius and reduce resistance
  • Thicken airway secretions

Correct Answer: Increase airway radius and reduce resistance

Q16. During forced expiration, airway collapse in small airways is promoted by:

  • Increase in intrapleural pressure making it exceed airway pressure
  • Decrease in alveolar pressure
  • Action of diaphragm pulling air out
  • Activation of central chemoreceptors

Correct Answer: Increase in intrapleural pressure making it exceed airway pressure

Q17. Pulmonary surfactant is produced by which cells?

  • Type I alveolar cells
  • Type II alveolar cells (pneumocytes)
  • Macrophages
  • Endothelial cells

Correct Answer: Type II alveolar cells (pneumocytes)

Q18. The primary determinant of oxygen diffusion from alveoli to blood is:

  • Alveolar ventilation only
  • Thickness and surface area of the alveolar-capillary membrane
  • Ventilatory rate alone
  • Total lung capacity

Correct Answer: Thickness and surface area of the alveolar-capillary membrane

Q19. Which law governs the solubility of a gas in a liquid at equilibrium with its partial pressure in a gas phase?

  • Boyle’s law
  • Henry’s law
  • Poiseuille’s law
  • Fick’s law

Correct Answer: Henry’s law

Q20. According to Poiseuille’s law, airflow through a tube is directly proportional to:

  • Length of the tube
  • Viscosity of the gas
  • Radius of the tube to the fourth power
  • Resistance of the tube

Correct Answer: Radius of the tube to the fourth power

Q21. The Hering–Breuer inflation reflex helps prevent overinflation by:

  • Stimulating inspiratory neurons during deep inspiration
  • Inhibiting inspiratory neurons as lungs inflate
  • Increasing respiratory rate during sleep
  • Enhancing surfactant release

Correct Answer: Inhibiting inspiratory neurons as lungs inflate

Q22. Ventilation-perfusion (V/Q) ratio reflects the relationship between:

  • Alveolar ventilation and pulmonary capillary blood flow
  • Tidal volume and dead space
  • Minute ventilation and metabolic rate
  • Oxygen content and hemoglobin concentration

Correct Answer: Alveolar ventilation and pulmonary capillary blood flow

Q23. A physiologic shunt leads to hypoxemia primarily because:

  • Ventilated alveoli are over-perfused
  • Perfused areas are not ventilated
  • Dead space is increased
  • Diffusion across the membrane is excessive

Correct Answer: Perfused areas are not ventilated

Q24. Forced vital capacity (FVC) is best described as:

  • Total air in the lungs after a normal inspiration
  • Volume expelled during a rapid, maximal expiration after maximal inspiration
  • Air remaining after a normal exhalation
  • Volume of one normal breath

Correct Answer: Volume expelled during a rapid, maximal expiration after maximal inspiration

Q25. Which parameter increases in obstructive lung disease like asthma?

  • Forced expiratory volume in 1 second (FEV1)
  • Airway resistance
  • Vital capacity
  • Lung compliance always decreases

Correct Answer: Airway resistance

Q26. The main effect of emphysema on breathing mechanics is:

  • Decreased lung compliance and increased elastic recoil
  • Loss of elastic fibers leading to increased compliance and airway collapse
  • Increased surfactant production
  • Reduced alveolar surface area but unchanged compliance

Correct Answer: Loss of elastic fibers leading to increased compliance and airway collapse

Q27. Fick’s law of diffusion indicates that gas transfer across a membrane is directly proportional to:

  • Membrane thickness
  • Partial pressure difference and surface area
  • Molecular weight squared
  • Viscosity of the gas

Correct Answer: Partial pressure difference and surface area

Q28. During hypoventilation, arterial CO2 levels typically:

  • Decrease (hypocapnia)
  • Remain unchanged
  • Increase (hypercapnia)
  • Are determined solely by oxygen levels

Correct Answer: Increase (hypercapnia)

Q29. The compliance curve of the lung shifts rightward in conditions where:

  • Lungs become stiffer (fibrosis)
  • Lungs become more compliant (emphysema)
  • Surfactant production increases
  • Airway resistance decreases

Correct Answer: Lungs become more compliant (emphysema)

Q30. Which receptors are activated by lung inflation and send inhibitory signals to the medullary respiratory center?

  • C-fiber receptors
  • Stretch receptors in airway smooth muscle (pulmonary stretch receptors)
  • Central chemoreceptors
  • Thermoreceptors

Correct Answer: Stretch receptors in airway smooth muscle (pulmonary stretch receptors)

Q31. Alveolar dead space is increased in pulmonary embolism because:

  • Alveoli are ventilated but not perfused
  • Alveoli are perfused but not ventilated
  • Surfactant levels rise
  • Airway resistance decreases

Correct Answer: Alveoli are ventilated but not perfused

Q32. Which ion change in cerebrospinal fluid primarily stimulates central chemoreceptors to increase ventilation?

  • Decrease in sodium concentration
  • Increase in hydrogen ion concentration (H+)
  • Decrease in potassium concentration
  • Increase in chloride concentration

Correct Answer: Increase in hydrogen ion concentration (H+)

Q33. Work of breathing increases with:

  • Decreased airway resistance and increased compliance
  • Increased airway resistance and decreased compliance
  • Reduced respiratory rate only
  • Increased alveolar oxygen tension

Correct Answer: Increased airway resistance and decreased compliance

Q34. Which of the following best describes the role of accessory muscles during respiration?

  • They are active during quiet breathing only
  • They assist during increased ventilatory demand or labored breathing
  • They reduce lung compliance
  • They are only used during sleep

Correct Answer: They assist during increased ventilatory demand or labored breathing

Q35. In obstructive diseases, the FEV1/FVC ratio is typically:

  • Increased
  • Normal
  • Decreased
  • Unchanged by airway obstruction

Correct Answer: Decreased

Q36. The primary function of pulmonary surfactant during small alveolar volumes is to:

  • Increase surface tension so alveoli collapse
  • Prevent alveolar collapse by reducing surface tension
  • Increase mucus clearance
  • Stimulate leukocyte activity

Correct Answer: Prevent alveolar collapse by reducing surface tension

Q37. Which factor causes a rightward shift in the oxygen-hemoglobin dissociation curve (facilitates O2 release)?

  • Decreased temperature
  • Increased pH (alkalosis)
  • Decreased CO2 and 2,3-BPG
  • Increased CO2, increased temperature, or increased 2,3-BPG

Correct Answer: Increased CO2, increased temperature, or increased 2,3-BPG

Q38. An increase in alveolar ventilation with constant metabolic CO2 production will:

  • Increase arterial CO2 tension (PaCO2)
  • Decrease PaCO2 and may cause respiratory alkalosis
  • Have no effect on PaCO2
  • Increase oxygen consumption

Correct Answer: Decrease PaCO2 and may cause respiratory alkalosis

Q39. The major determinant of airway resistance in the tracheobronchial tree is:

  • Number of alveoli
  • Total cross-sectional area of small airways
  • Lung volume only
  • Capillary blood flow

Correct Answer: Total cross-sectional area of small airways

Q40. Central chemoreceptors are most sensitive to changes in which of the following?

  • Arterial oxygen (PaO2)
  • Arterial pH directly
  • Cerebrospinal fluid CO2/pH
  • Blood glucose levels

Correct Answer: Cerebrospinal fluid CO2/pH

Q41. The elastic recoil of the lung is primarily due to:

  • Surface tension and elastic fibers in the lung parenchyma
  • Bronchial smooth muscle contraction
  • Surfactant alone
  • Airway dead space

Correct Answer: Surface tension and elastic fibers in the lung parenchyma

Q42. Which measurement indicates diffusion capacity of the lung for carbon monoxide (DLCO) is reduced?

  • Increased DLCO value
  • Unchanged DLCO
  • Decreased DLCO due to thickened alveolar membrane or reduced surface area
  • Increased pulmonary capillary volume only

Correct Answer: Decreased DLCO due to thickened alveolar membrane or reduced surface area

Q43. The main pharmacologic reason to administer supplemental oxygen is to:

  • Increase CO2 removal from tissues
  • Increase the fraction of inspired oxygen and raise arterial PO2
  • Directly stimulate respiratory muscles
  • Lower the alveolar ventilation rate

Correct Answer: Increase the fraction of inspired oxygen and raise arterial PO2

Q44. Which of the following increases anatomical dead space?

  • Tracheal intubation or mechanical ventilation with large tubing
  • Bronchodilation
  • Increased alveolar perfusion
  • Enhanced surfactant production

Correct Answer: Tracheal intubation or mechanical ventilation with large tubing

Q45. In restrictive lung disease, which pulmonary function change is characteristic?

  • Increased total lung capacity
  • Decreased total lung capacity and reduced compliance
  • Normal compliance with increased residual volume
  • Marked increase in airway resistance

Correct Answer: Decreased total lung capacity and reduced compliance

Q46. The main driver for passive expiration during quiet breathing is:

  • Active contraction of abdominal muscles
  • Elastic recoil of the lungs and chest wall
  • Voluntary neural input
  • Increased diaphragm activity

Correct Answer: Elastic recoil of the lungs and chest wall

Q47. The mechanism by which carbon dioxide crosses the alveolar-capillary membrane most effectively is:

  • Simple diffusion driven by partial pressure gradient
  • Active transport via ion pumps
  • Carrier-mediated facilitated diffusion only
  • Bulk flow through channels

Correct Answer: Simple diffusion driven by partial pressure gradient

Q48. Which condition will most likely increase work of breathing?

  • Low airway resistance and increased compliance
  • High airway resistance and low compliance
  • Use of accessory muscles during deep breathing only
  • Increased alveolar oxygen tension

Correct Answer: High airway resistance and low compliance

Q49. The primary effect of increased intrapulmonary (alveolar) pressure relative to atmospheric pressure is:

  • Air flows into the lungs
  • Air flows out of the lungs
  • Pleural space pressure becomes negative
  • Cardiac output increases

Correct Answer: Air flows out of the lungs

Q50. Which factor most directly reduces surface tension and stabilizes small alveoli to prevent atelectasis?

  • Mucus secretion
  • Pulmonary surfactant phospholipids
  • Type I pneumocytes’ cilia
  • High intrapleural pressure

Correct Answer: Pulmonary surfactant phospholipids

Leave a Comment