Q.1 Which of the following muscles is primarily responsible for quiet inspiration?
Diaphragm
External intercostals
Internal intercostals
Abdominal muscles
Explanation - During quiet inspiration, the diaphragm contracts and flattens, increasing the vertical dimension of the thoracic cavity, which draws air into the lungs.
Correct answer is: Diaphragm
Q.2 What is the main function of surfactant in the alveoli?
Transport of oxygen
Decrease surface tension
Increase mucus production
Stimulate cilia movement
Explanation - Pulmonary surfactant reduces the surface tension in alveoli, preventing their collapse during exhalation and reducing the work of breathing.
Correct answer is: Decrease surface tension
Q.3 Which gas has the highest partial pressure in alveolar air under normal conditions?
Oxygen
Carbon dioxide
Nitrogen
Water vapor
Explanation - Alveolar air contains mostly nitrogen (~74%), oxygen (~13-14%), carbon dioxide (~5-6%), and water vapor (~6%), making nitrogen the gas with the highest partial pressure.
Correct answer is: Nitrogen
Q.4 Which of the following changes occurs in the lungs during forced expiration?
Diaphragm contracts
External intercostals contract
Internal intercostals contract
Alveolar volume increases
Explanation - During forced expiration, internal intercostals contract to pull the ribs downward and inward, decreasing thoracic volume and pushing air out of the lungs.
Correct answer is: Internal intercostals contract
Q.5 The majority of carbon dioxide in the blood is transported as:
Dissolved CO2
Carbaminohemoglobin
Bicarbonate ions
Carbonic acid
Explanation - About 70% of CO2 is transported as bicarbonate ions (HCO3-) formed from CO2 and water via the enzyme carbonic anhydrase in red blood cells.
Correct answer is: Bicarbonate ions
Q.6 Which receptor type primarily senses changes in arterial CO2?
Peripheral chemoreceptors
Central chemoreceptors
Mechanoreceptors
Baroreceptors
Explanation - Central chemoreceptors in the medulla respond to changes in cerebrospinal fluid pH, which reflects arterial CO2 levels, and adjust ventilation accordingly.
Correct answer is: Central chemoreceptors
Q.7 The functional residual capacity (FRC) is defined as:
Total lung capacity minus vital capacity
Volume of air remaining after normal exhalation
Tidal volume plus inspiratory reserve volume
Maximum volume inhaled after normal inspiration
Explanation - FRC is the amount of air left in the lungs at the end of a normal passive exhalation, which helps prevent alveolar collapse.
Correct answer is: Volume of air remaining after normal exhalation
Q.8 Which of the following best describes the Haldane effect?
Oxygen binding decreases CO2 affinity of hemoglobin
CO2 binding increases oxygen affinity
CO2 stimulates red blood cell production
Oxygen stimulates bicarbonate formation
Explanation - The Haldane effect describes how oxygenated hemoglobin binds less CO2, promoting CO2 release in the lungs and CO2 uptake in the tissues.
Correct answer is: Oxygen binding decreases CO2 affinity of hemoglobin
Q.9 Which lung volume cannot be measured directly by spirometry?
Tidal volume
Inspiratory reserve volume
Residual volume
Expiratory reserve volume
Explanation - Residual volume, the air remaining in the lungs after maximal exhalation, cannot be measured directly by spirometry because it is always present in the lungs.
Correct answer is: Residual volume
Q.10 What is the primary driving force for pulmonary ventilation?
Alveolar pressure changes
Oxygen diffusion
Carbon dioxide diffusion
Blood pressure changes
Explanation - Ventilation occurs due to pressure differences between the alveoli and the atmosphere. Air moves into the lungs when alveolar pressure falls below atmospheric pressure.
Correct answer is: Alveolar pressure changes
Q.11 Which of the following causes a right shift in the oxyhemoglobin dissociation curve?
Decrease in temperature
Decrease in PCO2
Increase in 2,3-BPG
Alkalosis
Explanation - An increase in 2,3-BPG reduces hemoglobin's affinity for oxygen, facilitating oxygen release to tissues, which shifts the curve to the right.
Correct answer is: Increase in 2,3-BPG
Q.12 The normal resting alveolar ventilation rate is approximately:
4 L/min
12 L/min
6 L/min
500 mL/min
Explanation - Alveolar ventilation accounts for the air actually reaching the alveoli for gas exchange. At rest, it is around 4 L/min.
Correct answer is: 4 L/min
Q.13 Which structure prevents food from entering the trachea during swallowing?
Epiglottis
Uvula
Glottis
Vocal cords
Explanation - The epiglottis folds over the glottis during swallowing, directing food into the esophagus and preventing aspiration into the trachea.
Correct answer is: Epiglottis
Q.14 Which condition is characterized by the destruction of alveolar walls and reduced surface area for gas exchange?
Asthma
Chronic bronchitis
Emphysema
Pneumothorax
Explanation - Emphysema involves permanent enlargement of alveoli and destruction of their walls, impairing gas exchange and reducing lung elasticity.
Correct answer is: Emphysema
Q.15 Which respiratory parameter is primarily affected in restrictive lung diseases?
Tidal volume
Vital capacity
Residual volume
Dead space volume
Explanation - Restrictive lung diseases reduce lung expansion, decreasing total lung capacity and vital capacity, while residual volume may be normal.
Correct answer is: Vital capacity
Q.16 During exercise, which factor primarily increases ventilation?
Decrease in arterial oxygen
Increase in arterial CO2
Increase in temperature and pH changes
Increase in residual volume
Explanation - During exercise, ventilation increases due to multiple factors including increased body temperature, acidosis, and neural input from muscles, not solely due to O2 or CO2 changes.
Correct answer is: Increase in temperature and pH changes
Q.17 The term 'dead space' refers to:
Air that reaches alveoli
Air that does not participate in gas exchange
Total lung volume
Functional residual capacity
Explanation - Dead space is the portion of inspired air that remains in the conducting airways and does not reach alveoli for gas exchange.
Correct answer is: Air that does not participate in gas exchange
Q.18 Which gas law explains the diffusion of gases across the alveolar-capillary membrane?
Boyle’s Law
Charles’ Law
Henry’s Law
Dalton’s Law
Explanation - Henry’s Law states that the amount of gas dissolved in a liquid is proportional to its partial pressure, explaining gas exchange in the lungs.
Correct answer is: Henry’s Law
Q.19 Which of the following will increase pulmonary vascular resistance?
Hypoxia
Hypercapnia
Alkalosis
Exercise
Explanation - Hypoxic pulmonary vasoconstriction occurs in response to low alveolar oxygen, increasing pulmonary vascular resistance to divert blood to better-ventilated areas.
Correct answer is: Hypoxia
Q.20 Which component of blood carries most oxygen?
Plasma
Hemoglobin
White blood cells
Platelets
Explanation - Hemoglobin in red blood cells carries the majority of oxygen (~98%) in the blood, with only a small amount dissolved in plasma.
Correct answer is: Hemoglobin
Q.21 Which of the following is the main site of gas exchange in the lungs?
Trachea
Bronchi
Alveoli
Bronchioles
Explanation - Alveoli are tiny air sacs with thin walls surrounded by capillaries, providing a large surface area for efficient gas exchange.
Correct answer is: Alveoli
Q.22 Which statement best describes the Bohr effect?
CO2 binding to hemoglobin reduces oxygen release
Increased CO2 and H+ facilitate oxygen release
High oxygen increases CO2 affinity
pH has no effect on hemoglobin
Explanation - The Bohr effect describes how elevated CO2 and H+ (low pH) reduce hemoglobin's affinity for oxygen, enhancing oxygen delivery to tissues.
Correct answer is: Increased CO2 and H+ facilitate oxygen release
Q.23 Which respiratory rhythm center is located in the medulla oblongata?
Dorsal respiratory group
Ventral respiratory group
Apneustic center
Pneumotaxic center
Explanation - The dorsal respiratory group in the medulla primarily controls inspiration by sending signals to the diaphragm and external intercostals.
Correct answer is: Dorsal respiratory group
Q.24 Which of the following increases during hyperventilation?
Arterial PCO2
Arterial PO2
Arterial pH
Bicarbonate concentration
Explanation - Hyperventilation reduces arterial CO2, which decreases hydrogen ion concentration and leads to respiratory alkalosis, raising arterial pH.
Correct answer is: Arterial pH