Regulation of respiration MCQs With Answer

by

Regulation of respiration MCQs With Answer provides B.Pharm students a focused, exam-oriented review of respiratory physiology and pharmacology. This concise introduction covers respiratory centers, central and peripheral chemoreceptors, ventilation control, gas transport, reflexes (Hering–Breuer, J-receptors), and drug effects on breathing. Each well-crafted question emphasizes mechanisms, clinical correlations, and calculation-based concepts to strengthen understanding for pharmacology, physiology, and therapeutics. Keywords included: regulation of respiration, respiratory physiology MCQs, chemoreceptors, ventilation, pulmonary mechanics, and B.Pharm exam practice. Clear explanations and targeted practice prepare you for university tests and competitive exams. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which parameter do central chemoreceptors primarily respond to?

  • Arterial PO2
  • CSF pH
  • Arterial pH
  • Pulmonary stretch

Correct Answer: CSF pH

Q2. Where are the main peripheral chemoreceptors located?

  • Medulla oblongata
  • Carotid and aortic bodies
  • Bronchial mucosa
  • Alveolar epithelium

Correct Answer: Carotid and aortic bodies

Q3. The most potent immediate chemical stimulus that increases ventilation is:

  • Decreased arterial PO2
  • Decreased arterial pH
  • Increased arterial PCO2 (PaCO2)
  • Increased alveolar PO2

Correct Answer: Increased arterial PCO2 (PaCO2)

Q4. The Hering–Breuer inflation reflex is mediated by sensory fibers in which nerve?

  • Glossopharyngeal nerve (IX)
  • Phrenic nerve
  • Vagus nerve (X)
  • Trigeminal nerve (V)

Correct Answer: Vagus nerve (X)

Q5. The primary respiratory rhythm-generating network in the medulla is called:

  • Apneustic center
  • Pneumotaxic center
  • Pre-Bötzinger complex
  • Substantia nigra

Correct Answer: Pre-Bötzinger complex

Q6. Peripheral chemoreceptors are most strongly activated when arterial PO2 falls below approximately:

  • 100 mmHg
  • 80 mmHg
  • 60 mmHg
  • 40 mmHg

Correct Answer: 60 mmHg

Q7. The Bohr effect refers to which physiological phenomenon?

  • CO2 binding to hemoglobin increasing O2 affinity
  • Increased temperature causing left shift of O2-Hb curve
  • H+ and CO2 causing right shift of oxygen-hemoglobin dissociation curve
  • Hemoglobin releasing CO2 in the lungs

Correct Answer: H+ and CO2 causing right shift of oxygen-hemoglobin dissociation curve

Q8. The Haldane effect describes:

  • The decrease in CO2 content of blood with increased oxygenation of hemoglobin
  • An increase in hemoglobin’s affinity for O2 in the presence of CO2
  • Ventilation increase during exercise
  • Pulmonary vasoconstriction in hypoxia

Correct Answer: The decrease in CO2 content of blood with increased oxygenation of hemoglobin

Q9. Pulmonary surfactant primarily functions to:

  • Increase alveolar surface tension
  • Decrease lung compliance
  • Reduce alveolar surface tension and increase compliance
  • Prevent airway mucus secretion

Correct Answer: Reduce alveolar surface tension and increase compliance

Q10. Stimulation of pulmonary J (C-fiber) receptors typically produces which respiratory pattern?

  • Slow deep breathing
  • Rapid shallow breathing and dyspnea
  • Complete apnea only
  • No change in breathing

Correct Answer: Rapid shallow breathing and dyspnea

Q11. The ventral respiratory group (VRG) is primarily active during:

  • Quiet tidal breathing only
  • Sleep apnea
  • Forced breathing, generating expiratory signals
  • Only during swallowing

Correct Answer: Forced breathing, generating expiratory signals

Q12. The dorsal respiratory group (DRG) mainly integrates sensory input and controls which muscles?

  • Accessory expiratory muscles only
  • Intrinsic laryngeal muscles only
  • Inspiratory muscles including the diaphragm
  • Intercostal muscles exclusively

Correct Answer: Inspiratory muscles including the diaphragm

Q13. In metabolic acidosis, ventilatory compensation typically results in:

  • Hypoventilation to retain CO2
  • No change in ventilation
  • Hyperventilation to lower PaCO2
  • Only central chemoreceptor inhibition

Correct Answer: Hyperventilation to lower PaCO2

Q14. Opioid analgesics affect respiration by:

  • Stimulating peripheral chemoreceptors
  • Depressing medullary respiratory centers and reducing CO2 sensitivity
  • Increasing phrenic nerve firing
  • Enhancing Hering–Breuer reflex

Correct Answer: Depressing medullary respiratory centers and reducing CO2 sensitivity

Q15. Alveolar ventilation (VA) is calculated by which formula?

  • VA = Tidal volume × Respiratory rate
  • VA = (Tidal volume − Dead space) × Respiratory rate
  • VA = Minute ventilation + Dead space
  • VA = Inspiratory reserve volume × Respiratory rate

Correct Answer: VA = (Tidal volume − Dead space) × Respiratory rate

Q16. Typical anatomical dead space in a healthy adult is approximately:

  • 50 mL
  • 150 mL
  • 500 mL
  • 1000 mL

Correct Answer: 150 mL

Q17. Which mechanism helps reduce ventilation-perfusion (V/Q) mismatch in poorly ventilated lung regions?

  • Bronchodilation
  • Pulmonary vasodilation
  • Hypoxic pulmonary vasoconstriction
  • Increased surfactant production

Correct Answer: Hypoxic pulmonary vasoconstriction

Q18. Chronic hypercapnia, as seen in COPD, is compensated renal physiologically by:

  • Decreasing bicarbonate reabsorption
  • Increasing bicarbonate retention
  • Immediate elimination of H+ by lungs
  • Suppressing renal HCO3- generation

Correct Answer: Increasing bicarbonate retention

Q19. Central chemoreceptors respond to CO2 changes more slowly because:

  • CO2 cannot cross the blood-brain barrier
  • They respond directly to arterial O2
  • They detect changes via CSF pH after CO2 diffusion and buffering
  • They are insensitive to pH

Correct Answer: They detect changes via CSF pH after CO2 diffusion and buffering

Q20. Signals from the carotid body are transmitted to the brainstem primarily via which cranial nerve?

  • Vagus nerve (X)
  • Glossopharyngeal nerve (IX)
  • Facial nerve (VII)
  • Accessory nerve (XI)

Correct Answer: Glossopharyngeal nerve (IX)

Q21. The pneumotaxic center in the pons primarily functions to:

  • Prolong inspiration indefinitely
  • Inhibit inspiration to regulate respiratory rate and tidal volume
  • Initiate cough reflex
  • Control voluntary breath-holding

Correct Answer: Inhibit inspiration to regulate respiratory rate and tidal volume

Q22. The apneustic center in the lower pons is associated with:

  • Inhibition of cough reflex
  • Promotion of prolonged inspiratory gasps (apneusis)
  • Direct control of peripheral chemoreceptors
  • Regulation of alveolar macrophages

Correct Answer: Promotion of prolonged inspiratory gasps (apneusis)

Q23. Early increase in ventilation at the start of exercise is mainly driven by:

  • Changes in arterial PO2 and PCO2 only
  • Central command and proprioceptor input from muscles
  • Hypoxic pulmonary vasoconstriction
  • Renal compensation

Correct Answer: Central command and proprioceptor input from muscles

Q24. Which gas is diffusion-limited rather than perfusion-limited under normal resting conditions?

  • Nitrogen
  • Carbon monoxide (CO)
  • Oxygen (O2)
  • Helium

Correct Answer: Carbon monoxide (CO)

Q25. Anemia affects which of the following most directly?

  • Arterial PO2
  • Oxygen content of blood (CaO2)
  • Alveolar ventilation equation
  • Pulmonary surfactant levels

Correct Answer: Oxygen content of blood (CaO2)

Q26. Which receptors are primarily responsible for sensing changes in arterial H+ (acidosis) quickly?

  • Central chemoreceptors in medulla
  • Peripheral chemoreceptors in carotid and aortic bodies
  • Pulmonary stretch receptors
  • Baroreceptors in carotid sinus

Correct Answer: Peripheral chemoreceptors in carotid and aortic bodies

Q27. Carotid body glomus cells respond to hypoxia by:

  • Opening potassium channels leading to hyperpolarization
  • Depolarizing and releasing neurotransmitters to afferent fibers
  • Reducing blood flow to the carotid sinus
  • Increasing surfactant secretion

Correct Answer: Depolarizing and releasing neurotransmitters to afferent fibers

Q28. High-altitude exposure typically causes which initial changes in ventilation and acid-base status?

  • Decreased ventilation and metabolic acidosis
  • Increased ventilation and respiratory alkalosis
  • No change in ventilation and respiratory acidosis
  • Increased ventilation and metabolic acidosis

Correct Answer: Increased ventilation and respiratory alkalosis

Q29. Dizziness after hyperventilation is mainly due to:

  • Increased cerebral blood flow from high CO2
  • Decrease in PaO2
  • Cerebral vasoconstriction caused by decreased PaCO2
  • Peripheral chemoreceptor overactivation

Correct Answer: Cerebral vasoconstriction caused by decreased PaCO2

Q30. The respiratory quotient (RQ) for pure carbohydrate metabolism is approximately:

  • 0.7
  • 0.8
  • 1.0
  • 1.2

Correct Answer: 1.0

Q31. Fever affects ventilation by:

  • Decreasing metabolic rate and ventilation
  • Increasing metabolic rate and ventilation
  • Only altering chemoreceptor sensitivity to oxygen
  • Suppressing respiratory centers permanently

Correct Answer: Increasing metabolic rate and ventilation

Q32. A commonly used respiratory stimulant in neonatal apnea is:

  • Naloxone
  • Doxapram
  • Diltiazem
  • Propranolol

Correct Answer: Doxapram

Q33. Apneustic breathing pattern is most likely caused by lesions in:

  • Medulla oblongata
  • Upper spinal cord
  • Pons
  • Cerebral cortex

Correct Answer: Pons

Q34. Carbon dioxide crosses the blood–brain barrier mainly as:

  • Bicarbonate ion (HCO3−)
  • Hydrogen ion (H+)
  • Molecular CO2 which then forms H+ in CSF
  • Carbamino compounds

Correct Answer: Molecular CO2 which then forms H+ in CSF

Q35. The phrenic nerve that innervates the diaphragm arises from which spinal segments?

  • C1–C3
  • C3–C5
  • T1–T4
  • L1–L3

Correct Answer: C3–C5

Q36. Pulmonary compliance is decreased in which condition?

  • Pulmonary fibrosis
  • Emphysema
  • Pulmonary edema only increases compliance
  • Normal aging always increases compliance

Correct Answer: Pulmonary fibrosis

Q37. Increasing temperature shifts the oxygen-hemoglobin dissociation curve in which direction?

  • Left shift, increasing O2 affinity
  • Right shift, decreasing O2 affinity
  • No change in curve position
  • Causes a vertical shift only

Correct Answer: Right shift, decreasing O2 affinity

Q38. In chronic CO2 retention (hypoventilatory states), administering high inspired oxygen can cause:

  • Increased respiratory drive in all patients
  • No change in ventilation
  • Suppression of hypoxic drive and further respiratory depression in some COPD patients
  • Immediate improvement of CO2 elimination regardless of ventilation

Correct Answer: Suppression of hypoxic drive and further respiratory depression in some COPD patients

Q39. Minute ventilation (VE) is defined as:

  • Tidal volume × Respiratory rate
  • Alveolar ventilation + Dead space
  • Inspiratory capacity × Respiratory rate
  • Functional residual capacity × Respiratory rate

Correct Answer: Tidal volume × Respiratory rate

Q40. The majority of CO2 in blood is transported as:

  • Dissolved CO2 in plasma
  • Carbaminohemoglobin exclusively
  • Bicarbonate ion (HCO3−)
  • Bound to plasma proteins only

Correct Answer: Bicarbonate ion (HCO3−)

Q41. Hypoventilation leads to which acid–base disturbance?

  • Respiratory alkalosis
  • Respiratory acidosis
  • Metabolic alkalosis
  • Metabolic acidosis

Correct Answer: Respiratory acidosis

Q42. The “ramp” signal from inspiratory neurons is characterized by:

  • A sudden burst of activity at the end of inspiration
  • Gradual increase in inspiratory neuronal firing during inspiration
  • Continuous inhibition of inspiration
  • Only activity during expiration

Correct Answer: Gradual increase in inspiratory neuronal firing during inspiration

Q43. Chronic hypoxemia increases ventilatory sensitivity mainly via which mechanism?

  • Downregulation of carotid body activity
  • Upregulation of carotid body sensitivity and increased afferent firing
  • Suppression of medullary centers permanently
  • Increased alveolar surface tension

Correct Answer: Upregulation of carotid body sensitivity and increased afferent firing

Q44. Carboxyhemoglobinemia from carbon monoxide exposure causes:

  • Increased PaO2 and decreased O2 content
  • Normal PaO2 but decreased O2 content due to CO occupying hemoglobin
  • Decreased PaO2 only
  • No effect on oxygen delivery

Correct Answer: Normal PaO2 but decreased O2 content due to CO occupying hemoglobin

Q45. Which pulmonary receptors are slowly adapting and mediate the inflation reflex?

  • Rapidly adapting irritant receptors (RARs)
  • Slowly adapting stretch receptors (SARs)
  • J receptors
  • Baroreceptors

Correct Answer: Slowly adapting stretch receptors (SARs)

Q46. In metabolic acidosis, which receptors primarily drive the acute ventilatory response?

  • Central chemoreceptors only
  • Peripheral chemoreceptors (carotid bodies)
  • Pulmonary stretch receptors
  • Digestive tract chemoreceptors

Correct Answer: Peripheral chemoreceptors (carotid bodies)

Q47. An increased alveolar-arterial (A–a) O2 gradient is consistent with which condition?

  • Shunt, V/Q mismatch, or diffusion limitation (e.g., pulmonary fibrosis)
  • Hypoventilation due to central depression only
  • Pure anemia without lung disease
  • Hyperventilation causing low PaCO2

Correct Answer: Shunt, V/Q mismatch, or diffusion limitation (e.g., pulmonary fibrosis)

Q48. Ventilation–perfusion ratio (V/Q) at the apex of a normal upright lung is typically:

  • Less than 0.5
  • Approximately 1.0
  • Greater than 1.0
  • Equal to alveolar ventilation only

Correct Answer: Greater than 1.0

Q49. Which of the following best describes perfusion-limited gas exchange?

  • Exchange limited by diffusion across the alveolar membrane regardless of blood flow
  • Exchange increases with increased blood flow and equilibrium is reached rapidly (e.g., N2O)
  • Occurs only for CO2 and never for O2
  • Only relevant at extremely high altitudes

Correct Answer: Exchange increases with increased blood flow and equilibrium is reached rapidly (e.g., N2O)

Q50. During exercise, which change in the oxygen-hemoglobin dissociation curve facilitates oxygen unloading to tissues?

  • Left shift due to decreased temperature and decreased CO2
  • Right shift due to increased temperature, CO2, and H+
  • No shift occurs during exercise
  • Curve becomes steeper without shifting

Correct Answer: Right shift due to increased temperature, CO2, and H+

Leave a Comment