Regulation of respiration MCQs With Answer

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Regulation of respiration MCQs With Answer

The regulation of respiration is a core topic for B.Pharm students studying respiratory physiology and pharmacology. This introduction covers central and peripheral respiratory centers, chemoreceptor control, pulmonary ventilation, gas exchange, acid-base balance, and pharmacological effects on breathing. Emphasis is on mechanisms—central chemoreceptors responding to CO2 and CSF pH, peripheral carotid and aortic bodies sensing O2, H+ and CO2, reflexes like Hering–Breuer, and drug-induced respiratory depression by opioids or anesthetics. Understanding these concepts aids rational drug therapy and respiratory management in clinical contexts. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which structure contains the primary central chemoreceptors that respond to changes in CSF pH and CO2?

  • Carotid bodies
  • Aortic bodies
  • Medullary respiratory center (ventral and dorsal respiratory groups)
  • Pontine respiratory group

Correct Answer: Medullary respiratory center (ventral and dorsal respiratory groups)

Q2. Peripheral chemoreceptors that detect arterial PO2 are located in which of the following?

  • Medulla oblongata
  • Carotid bodies
  • Alveolar epithelium
  • Bronchial smooth muscle

Correct Answer: Carotid bodies

Q3. Which stimulus most potently increases ventilation under normal physiological conditions?

  • Decrease in arterial PO2 from 100 to 90 mmHg
  • Increase in arterial HCO3-
  • Increase in arterial PCO2
  • Decrease in body temperature

Correct Answer: Increase in arterial PCO2

Q4. Central chemoreceptors primarily sense changes in which of the following?

  • Arterial PO2 directly
  • Cerebrospinal fluid H+ concentration
  • Arterial hemoglobin concentration
  • Pulmonary stretch

Correct Answer: Cerebrospinal fluid H+ concentration

Q5. The Hering–Breuer inflation reflex primarily prevents which of the following?

  • Hypoventilation during exercise
  • Overinflation of the lungs
  • Bronchoconstriction
  • Increase in cardiac output

Correct Answer: Overinflation of the lungs

Q6. Which ion changes in CSF mediate the effect of raised arterial PCO2 on ventilation?

  • Decrease in CSF Na+
  • Increase in CSF H+
  • Decrease in CSF K+
  • Increase in CSF Cl-

Correct Answer: Increase in CSF H+

Q7. Carotid body glomus cells respond to hypoxia by releasing neurotransmitters. Which neurotransmitter is commonly involved?

  • Acetylcholine
  • Dopamine
  • Glutathione
  • Insulin

Correct Answer: Dopamine

Q8. In chronic respiratory acidosis, the kidneys compensate primarily by which mechanism?

  • Decreasing HCO3- reabsorption
  • Increasing HCO3- reabsorption and H+ secretion
  • Increasing respiratory rate to lower PCO2
  • Decreasing renal ammonium excretion

Correct Answer: Increasing HCO3- reabsorption and H+ secretion

Q9. The normal arterial PCO2 in a healthy adult is approximately:

  • 20 mmHg
  • 40 mmHg
  • 60 mmHg
  • 80 mmHg

Correct Answer: 40 mmHg

Q10. Opioids depress respiration mainly by acting on which of the following?

  • Peripheral chemoreceptors
  • Medullary respiratory centers via mu-opioid receptors
  • Bronchial smooth muscle relaxation
  • Carotid sinus baroreceptors

Correct Answer: Medullary respiratory centers via mu-opioid receptors

Q11. Which reflex is activated by pulmonary C-fiber (J receptor) stimulation and can produce rapid shallow breathing and bronchoconstriction?

  • Hering–Breuer inflation reflex
  • Cough reflex
  • Pulmonary chemoreflex

Correct Answer: Pulmonary chemoreflex

Q12. During acute hypoxia, which chemoreceptor response predominates in increasing ventilation?

  • Central chemoreceptors
  • Peripheral chemoreceptors
  • Baroreceptors
  • Stretch receptors

Correct Answer: Peripheral chemoreceptors

Q13. Which change occurs in the ventilatory response to CO2 during metabolic alkalosis?

  • Ventilation increases for a given PCO2
  • Ventilation decreases for a given PCO2
  • No change in ventilatory response
  • Peripheral chemoreceptor sensitivity increases

Correct Answer: Ventilation decreases for a given PCO2

Q14. The dorsal respiratory group primarily contributes to which phase of breathing?

  • Expiration by active contraction
  • Inspiration by integrating sensory input and generating inspiratory rhythm
  • Pontine modulation of respiration
  • Generation of cough reflex only

Correct Answer: Inspiration by integrating sensory input and generating inspiratory rhythm

Q15. Which drug is used as a respiratory stimulant in clinical settings acting on peripheral chemoreceptors?

  • Morphine
  • Doxapram
  • Propranolol
  • Diazepam

Correct Answer: Doxapram

Q16. In COPD patients with chronic hypercapnia, the drive to breathe may become more dependent on:

  • Central chemoreceptor CO2 sensitivity
  • Peripheral chemoreceptor hypoxic drive
  • Renal compensation only
  • Baroreceptor-mediated drive

Correct Answer: Peripheral chemoreceptor hypoxic drive

Q17. Which of the following best describes the effect of hyperventilation on arterial pH and PCO2?

  • Decrease pH, increase PCO2
  • Increase pH, decrease PCO2
  • No change in pH, increase PCO2
  • Decrease pH, decrease PCO2

Correct Answer: Increase pH, decrease PCO2

Q18. The pontine respiratory group (pneumotaxic center) primarily influences which aspect of breathing?

  • Tidal volume only
  • Inspiration termination and respiratory rate modulation
  • Alveolar gas diffusion
  • Peripheral chemoreceptor sensitivity

Correct Answer: Inspiration termination and respiratory rate modulation

Q19. Which receptor type in the lungs responds to rapid lung inflation and contributes to the Hering–Breuer reflex?

  • Slowly adapting pulmonary stretch receptors
  • Rapidly adapting irritant receptors
  • Type II pneumocytes
  • Bronchial C-fibers

Correct Answer: Slowly adapting pulmonary stretch receptors

Q20. High altitude acclimatization initially increases ventilation due to stimulation of which factor?

  • Decreased atmospheric pressure leading to lower inspired PO2 sensed by peripheral chemoreceptors
  • Increased ambient CO2
  • Renal failure
  • Elevation in body temperature

Correct Answer: Decreased atmospheric pressure leading to lower inspired PO2 sensed by peripheral chemoreceptors

Q21. Which of the following is true regarding central chemoreceptor response to chronic hypercapnia?

  • Sensitivity to CO2 is permanently increased
  • CSF buffering and renal compensation reduce central chemoreceptor response over time
  • Peripheral chemoreceptors stop functioning
  • Ventilation increases progressively without limit

Correct Answer: CSF buffering and renal compensation reduce central chemoreceptor response over time

Q22. Pulmonary stretch receptor signals travel to the brainstem via which nerve?

  • Glossopharyngeal nerve (CN IX)
  • Vagus nerve (CN X)
  • Phrenic nerve
  • Hypoglossal nerve (CN XII)

Correct Answer: Vagus nerve (CN X)

Q23. Which condition would shift the ventilation-perfusion (V/Q) matching and stimulate local hypoxic vasoconstriction?

  • High alveolar PO2
  • Poorly ventilated alveolus with low PO2
  • Systemic hypotension
  • Increased cardiac output

Correct Answer: Poorly ventilated alveolus with low PO2

Q24. The primary molecular sensor in carotid body glomus cells for hypoxia likely involves inhibition of which channel?

  • Voltage-gated sodium channels
  • SGLT glucose transporters
  • NMDA receptors

Correct Answer: O2-sensitive potassium channels (K+ channels)

Q25. Which ventilatory change is expected during moderate exercise in a healthy individual?

  • Minute ventilation increases primarily due to increased tidal volume and later increased respiratory rate
  • Minute ventilation decreases due to fatigue
  • Only respiratory rate increases while tidal volume decreases
  • Alveolar ventilation remains unchanged

Correct Answer: Minute ventilation increases primarily due to increased tidal volume and later increased respiratory rate

Q26. In metabolic acidosis, ventilation typically changes in which way to compensate?

  • Hypoventilation to retain CO2
  • Hyperventilation to lower PCO2
  • No change in ventilation
  • Intermittent apnea

Correct Answer: Hyperventilation to lower PCO2

Q27. Which neurotransmitter has been implicated in central chemoreceptor signaling and modulation of respiratory drive?

  • GABA
  • Serotonin (5-HT)
  • Insulin
  • Histamine only in peripheral tissues

Correct Answer: Serotonin (5-HT)

Q28. Sleep-related hypoventilation is primarily due to decreased activity of which control mechanism?

  • Behavioral cortical drive to breathe
  • Peripheral chemoreceptor sensitivity enhancement
  • Increased metabolic rate
  • Increased stretch receptor activity

Correct Answer: Behavioral cortical drive to breathe

Q29. Which change characterizes acute mountain sickness in terms of ventilation and blood gases?

  • Hypoventilation, increased PCO2, respiratory acidosis
  • Hyperventilation, decreased PCO2, respiratory alkalosis
  • No change in ventilation or blood gases
  • Increased PCO2 with metabolic alkalosis

Correct Answer: Hyperventilation, decreased PCO2, respiratory alkalosis

Q30. Which of the following drugs reduces ventilatory response to CO2 and is used as a sedative or anesthetic?

  • Almitrine
  • Opioids (e.g., morphine)
  • Doxapram
  • Acetazolamide

Correct Answer: Opioids (e.g., morphine)

Q31. Acetazolamide stimulates ventilation in altitude sickness by which mechanism?

  • Direct stimulation of central chemoreceptors
  • Inducing metabolic acidosis via carbonic anhydrase inhibition, increasing ventilation
  • Increasing hemoglobin’s affinity for oxygen
  • Blocking peripheral chemoreceptors

Correct Answer: Inducing metabolic acidosis via carbonic anhydrase inhibition, increasing ventilation

Q32. Which process explains why central chemoreceptors do not directly sense arterial H+?

  • Blood-brain barrier prevents rapid H+ movement; CO2 diffuses and forms H+ in CSF
  • Arterial H+ is irrelevant to ventilation control
  • CSF has no buffering capacity
  • Arterial H+ binds hemoglobin preventing sensing

Correct Answer: Blood-brain barrier prevents rapid H+ movement; CO2 diffuses and forms H+ in CSF

Q33. Which reflex increases ventilation in response to increased metabolic activity of exercising muscles?

  • Hering–Breuer reflex
  • Peripheral chemoreceptor reflex due to hypoxemia only
  • Exercise hyperpnea mediated by central command and muscle afferents
  • Cough reflex

Correct Answer: Exercise hyperpnea mediated by central command and muscle afferents

Q34. Alveolar hypoventilation leads to which of the following blood gas changes?

  • Decreased PaCO2 and respiratory alkalosis
  • Increased PaCO2 and respiratory acidosis
  • Increased PaO2 and metabolic alkalosis
  • No change in PaCO2

Correct Answer: Increased PaCO2 and respiratory acidosis

Q35. Which receptor type mediates the cough reflex from the upper airways?

  • Pulmonary stretch receptors only
  • Rapidly adapting (irritant) receptors
  • Olfactory receptors
  • Type I pneumocytes

Correct Answer: Rapidly adapting (irritant) receptors

Q36. In a patient with metabolic alkalosis, what is the expected compensatory respiratory response?

  • Hyperventilation to decrease pH
  • Hypoventilation to retain CO2 and raise H+ concentration
  • No respiratory compensation
  • Increased peripheral chemoreceptor firing due to low PO2

Correct Answer: Hypoventilation to retain CO2 and raise H+ concentration

Q37. Which physiological change reduces central chemoreceptor sensitivity to CO2 during chronic adaptation to high altitude?

  • Decrease in cerebral blood flow only
  • Renal compensation increasing plasma HCO3- and CSF HCO3- levels
  • Loss of peripheral chemoreceptors
  • Permanent cerebral acidosis

Correct Answer: Renal compensation increasing plasma HCO3- and CSF HCO3- levels

Q38. Which of the following best describes the mechanism of respiratory depression caused by benzodiazepines?

  • Blockade of peripheral chemoreceptors
  • Enhancement of GABAergic inhibition in brainstem respiratory centers
  • Direct inhibition of diaphragm muscle contraction
  • Activation of carotid body glomus cells

Correct Answer: Enhancement of GABAergic inhibition in brainstem respiratory centers

Q39. The term “ventilatory equivalent for oxygen (VE/VO2)” refers to:

  • The ratio of minute ventilation to oxygen consumption
  • Alveolar ventilation per breath
  • Arterial O2 content divided by CO2 production
  • Dead space volume only

Correct Answer: The ratio of minute ventilation to oxygen consumption

Q40. Which physiological response helps maintain cerebral pH during chronic hypercapnia?

  • Increased CSF bicarbonate via renal compensation
  • Decreased hemoglobin oxygen affinity
  • Increased pulmonary vasoconstriction
  • Immediate CSF acid removal by CSF pumps

Correct Answer: Increased CSF bicarbonate via renal compensation

Q41. Which of the following best explains the blunted hypoxic ventilatory response in chronic smokers?

  • Permanent destruction of medullary centers
  • Reduced peripheral chemoreceptor sensitivity due to chronic nicotine and hypercapnia effects
  • Increased baroreceptor activity only
  • Improved oxygen delivery due to increased hemoglobin

Correct Answer: Reduced peripheral chemoreceptor sensitivity due to chronic nicotine and hypercapnia effects

Q42. Which accessory respiratory muscle is primarily recruited during forced inspiration?

  • Internal intercostals
  • Sternocleidomastoid
  • Abdominal rectus
  • Transversus thoracis

Correct Answer: Sternocleidomastoid

Q43. Which of the following is a consequence of persistent hypercapnia on peripheral chemoreceptor function?

  • Peripheral chemoreceptor sensitivity increases indefinitely
  • Sensory adaptation may occur reducing responsiveness to CO2
  • Carotid bodies hypertrophy and stop functioning
  • No change; only central chemoreceptors adapt

Correct Answer: Sensory adaptation may occur reducing responsiveness to CO2

Q44. The phrenic nerve, which controls the diaphragm, originates from which spinal nerve roots?

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

Correct Answer: C3–C5

Q45. Which pharmacologic agent is known to enhance central respiratory drive by antagonizing GABA receptors and is occasionally used in specific overdose situations?

  • Flumazenil
  • Naloxone
  • Midazolam
  • Fentanyl

Correct Answer: Flumazenil

Q46. Ventilatory control during exercise involves feedforward signals from the motor cortex. This is called:

  • Peripheral chemoreception
  • Central command
  • Hering–Breuer reflex
  • Baroreflex

Correct Answer: Central command

Q47. Which acid-base disturbance is expected in a patient with opioid overdose causing prolonged hypoventilation?

  • Respiratory alkalosis
  • Respiratory acidosis with elevated PaCO2
  • Metabolic acidosis with low HCO3- only
  • Metabolic alkalosis

Correct Answer: Respiratory acidosis with elevated PaCO2

Q48. Which factor most strongly stimulates ventilation in healthy individuals during incremental exercise?

  • Arterial hypoxemia occurring early in exercise
  • Neural feedforward signals and increased body temperature
  • Major increases in arterial PCO2
  • Decreased metabolic CO2 production

Correct Answer: Neural feedforward signals and increased body temperature

Q49. Which clinical test reflects central chemoreceptor responsiveness to CO2?

  • Hypoxic ventilatory response test using reduced O2 only
  • Hypercapnic ventilatory response test (inhaled CO2 challenge)
  • Pulmonary function test measuring FEV1
  • Pulse oximetry during sleep

Correct Answer: Hypercapnic ventilatory response test (inhaled CO2 challenge)

Q50. In heart failure patients, pulmonary congestion can stimulate J receptors. This leads to which respiratory pattern?

  • Slow, deep breathing with prolonged inspiratory time
  • Rapid shallow breathing and dyspnea
  • Complete apnea
  • Unchanged breathing pattern

Correct Answer: Rapid shallow breathing and dyspnea

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