Breathing and Exchange of Gases

Topic: Respiration in Humans; Subtopic: Sequence of Events in Respiration

Keyword Definitions:

• Respiration: A biochemical process involving intake of oxygen and release of carbon dioxide during oxidation of organic molecules to produce energy.

• Pulmonary Ventilation: The physical process of breathing in and out of air through lungs.

• Alveoli: Thin-walled air sacs in lungs where exchange of gases occurs between air and blood.

• Gas Exchange: Movement of O2 and CO2 between alveoli, blood, and tissues by diffusion.

• Cellular Respiration: Utilisation of O2 by cells to produce energy (ATP) through oxidative catabolism of food molecules.

Lead Question - 2024 (Jhajjhar)

In humans, the process of respiration involves the following steps:
A. Diffusion of gases across alveolar membrane
B. Diffusion of gases between blood and tissues
C. Transport of gases by blood
D. Utilisation of O2 by the cells for catabolic reactions
E. Breathing or pulmonary ventilation

Choose the correct sequence of steps from the options given below:

1. A → E → B → C → D
2. C → E → A → B → D
3. B → D → C → E → A
4. E → A → C → B → D

Explanation: The correct sequence of respiration steps is E → A → C → B → D. Breathing (E) allows air to enter the lungs. Then gas exchange occurs across alveolar membrane (A). Blood transports these gases (C), which then diffuse between blood and tissues (B). Finally, cells use oxygen for metabolism (D). This entire process ensures continuous oxygen supply and removal of carbon dioxide for maintaining cellular energy balance.

1. (Guessed Question)
During external respiration, which process occurs?
1. Exchange of O2 and CO2 between alveoli and blood
2. Exchange of gases between blood and tissues
3. Breakdown of glucose into pyruvate
4. Production of ATP inside mitochondria

Explanation: External respiration is the exchange of O2 and CO2 between alveolar air and pulmonary blood through diffusion. It occurs across the alveolar-capillary membrane. This step ensures oxygen enters the blood and carbon dioxide leaves it, maintaining proper gas balance. Hence, option 1 is correct.

2. (Guessed Question)
Which structure of the respiratory system has the largest surface area for gas exchange?
1. Trachea
2. Bronchi
3. Alveoli
4. Larynx

Explanation: Alveoli have a large surface area and thin epithelial walls, providing the ideal site for diffusion of gases. Millions of alveoli increase the efficiency of oxygen and carbon dioxide exchange in the lungs. Thus, alveoli are the main site of gaseous exchange.

3. (Guessed Question)
Oxygen transport in blood occurs mainly through:
1. Dissolved form in plasma
2. Binding with hemoglobin
3. Attached to white blood cells
4. Reacting with plasma proteins

Explanation: Nearly 97% of oxygen is transported bound to hemoglobin as oxyhemoglobin (HbO2). Only about 3% remains dissolved in plasma. This efficient binding facilitates oxygen delivery to tissues according to metabolic demand, maintaining body homeostasis. Hence, option 2 is correct.

4. (Guessed Question)
Which enzyme helps in the conversion of CO2 to carbonic acid inside RBCs?
1. Carbonic anhydrase
2. Catalase
3. Peroxidase
4. Amylase

Explanation: Carbonic anhydrase catalyzes the reversible reaction between CO2 and water to form carbonic acid (H2CO3). This enzyme facilitates rapid CO2 transport in blood and its release during expiration. The process maintains acid–base balance efficiently. Hence, option 1 is correct.

5. (Guessed Question)
Which part of the brain regulates the rate of respiration?
1. Hypothalamus
2. Cerebellum
3. Medulla oblongata
4. Cerebrum

Explanation: The respiratory rhythm center located in the medulla oblongata controls the rate and depth of breathing. It responds to CO2 concentration and maintains the acid-base balance in blood by adjusting ventilation rate. Therefore, option 3 is correct.

6. (Guessed Question)
The primary site of exchange of gases between blood and tissues is:
1. Arteries
2. Veins
3. Capillaries
4. Lymphatic vessels

Explanation: Capillaries have thin walls that allow diffusion of oxygen and carbon dioxide between blood and tissue cells. Oxygen diffuses into tissues while carbon dioxide moves into blood. Hence, option 3 is correct. This exchange maintains the body’s oxygen supply and removes metabolic waste efficiently.

7. (Assertion–Reason Type)
Assertion (A): Hemoglobin has a high affinity for oxygen at lungs.
Reason (R): Partial pressure of oxygen (pO2) is high and that of carbon dioxide (pCO2) is low in alveoli.
1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, R is false.
4. A is false, R is true.

Explanation: Both Assertion and Reason are true, and Reason correctly explains Assertion. High pO2 and low pCO2 in alveoli favor oxyhemoglobin formation, enhancing oxygen loading at lungs. Hence, option 1 is correct.

8. (Matching Type)
Match the following processes with their sites:
A. Diffusion of gases – (i) Alveoli
B. Transport of gases – (ii) Blood
C. Regulation of breathing – (iii) Medulla
D. Cellular respiration – (iv) Mitochondria

1. A–i, B–ii, C–iii, D–iv
2. A–ii, B–iii, C–iv, D–i
3. A–iv, B–i, C–ii, D–iii
4. A–iii, B–iv, C–ii, D–i

Explanation: Diffusion of gases occurs in alveoli (A–i), transport in blood (B–ii), regulation in medulla (C–iii), and cellular respiration in mitochondria (D–iv). Thus, option 1 is correct. Each step is vital for maintaining oxygen balance and energy production.

9. (Fill in the Blanks)
Each hemoglobin molecule can carry ______ molecules of oxygen.
1. Two
2. Four
3. Six
4. Eight

Explanation: Each hemoglobin molecule has four polypeptide chains, each containing one heme group. Every heme group binds one O2 molecule; hence, each hemoglobin carries four oxygen molecules in total. This ensures efficient oxygen transport throughout the body. Correct answer: four.

10. (Choose the Correct Statements)
Statement I: Breathing rate increases during exercise.
Statement II: Increased CO2 concentration stimulates respiratory center in medulla.
1. Both statements are true.
2. Both statements are false.
3. Only Statement I true.
4. Only Statement II true.

Explanation: Both statements are true. During exercise, more CO2 is produced due to enhanced metabolism. Elevated CO2 levels activate chemoreceptors, stimulating the respiratory center in medulla to increase breathing rate for maintaining oxygen supply and pH balance. Hence, option 1 is correct.

Subtopic: Respiratory Disorders and Their Causes

Keyword Definitions:

• Emphysema: A chronic respiratory disorder where alveolar walls are damaged, decreasing the respiratory surface area.

• Asbestosis: Lung disease caused by inhaling asbestos fibers, leading to fibrosis and scarring of lung tissue.

• Asthma: A condition causing difficulty in breathing due to inflammation of bronchi and bronchioles.

• Fibrosis: Formation of excessive fibrous tissue in the lungs, reducing elasticity and gas exchange capacity.

• Bronchioles: Small branches of bronchi that regulate air passage and resistance in the lungs.

• Alveoli: Tiny air sacs where gas exchange occurs between air and blood.

Lead Question - 2024 (Jhajjhar)
Match List-I with List-II:
List-I List-II
A. Emphysema I. Proliferation of fibrous tissues
B. Asbestosis II. Alveolar walls are damaged and respiratory surface is decreased
C. Asthma III. Serious lung damage
D. Fibrosis IV. Difficulty in breathing due to inflammation of bronchi and bronchioles
1. A-I, B-III, C-IV, D-II
2. A-II, B-III, C-IV, D-I
3. A-IV, B-III, C-II, D-I
4. A-I, B-II, C-IV, D-III

Explanation: Emphysema results from damage to alveolar walls, reducing gas exchange area. Asbestosis causes severe lung damage due to asbestos fibers. Asthma leads to breathing difficulty from bronchi inflammation, while Fibrosis causes fibrous tissue buildup in the lungs. Therefore, the correct match is A-II, B-III, C-IV, D-I, i.e., Option 2.

1. Which respiratory disorder is associated with destruction of alveolar walls?
1. Asthma
2. Bronchitis
3. Emphysema
4. Pneumonia

In Emphysema, the alveolar walls are destroyed due to prolonged exposure to irritants like cigarette smoke. This reduces the surface area for gas exchange, leading to shortness of breath and reduced oxygen intake. Therefore, the correct answer is Option 3 (Emphysema).

2. Which occupational disease is caused by asbestos exposure?
1. Silicosis
2. Asbestosis
3. Fibrosis
4. Pneumoconiosis

Prolonged exposure to asbestos dust leads to Asbestosis, a chronic lung condition characterized by fibrosis, breathlessness, and reduced lung function. It is an occupational hazard found among workers handling asbestos materials. Hence, the correct answer is Option 2 (Asbestosis).

3. Which of the following statements about Asthma is correct?
1. It causes inflammation of alveoli.
2. It results in fibrosis of lungs.
3. It involves constriction of bronchi and bronchioles.
4. It leads to alveolar rupture.

In Asthma, bronchi and bronchioles undergo inflammation and narrowing due to allergic or environmental triggers. This leads to difficulty in breathing and wheezing sounds. The alveoli remain unaffected. Therefore, the correct answer is Option 3.

4. Assertion-Reason Type:
Assertion (A): Smoking is one of the main causes of Emphysema.
Reason (R): Smoking causes permanent dilation of alveoli and destruction of their walls.
1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Cigarette smoke contains harmful chemicals that destroy alveolar walls, reducing elasticity and causing air trapping, characteristic of Emphysema. Hence, both statements are true, and the Reason correctly explains the Assertion. The correct answer is Option 1.

5. Match the following:
List-I (Disease) — List-II (Cause)
A. Bronchitis — I. Asbestos exposure
B. Emphysema — II. Smoke and air pollutants
C. Asbestosis — III. Inflammation of bronchi
D. Fibrosis — IV. Proliferation of connective tissue
1. A-III, B-II, C-I, D-IV
2. A-I, B-III, C-IV, D-II
3. A-II, B-I, C-III, D-IV
4. A-IV, B-II, C-I, D-III

Bronchitis results from inflammation of bronchi, Emphysema from air pollutants, Asbestosis from asbestos fibers, and Fibrosis from connective tissue growth. Thus, the correct matching is A-III, B-II, C-I, D-IV, i.e., Option 1.

6. Which of the following is a symptom of Fibrosis?
1. Increased oxygen absorption
2. Increased lung elasticity
3. Stiffness of lungs and reduced lung capacity
4. Excess mucus secretion

In Fibrosis, fibrous tissue replaces healthy lung tissue, leading to stiffness, reduced elasticity, and lower gas exchange efficiency. This causes shortness of breath and fatigue. Hence, the correct answer is Option 3 (Stiffness of lungs and reduced lung capacity).

7. Fill in the Blank:
Asbestosis is caused by prolonged exposure to __________ dust.

Asbestosis results from long-term inhalation of asbestos fibers, a material used in construction and insulation. The fibers damage lung tissue, leading to fibrosis and chronic respiratory problems. Therefore, the correct word to fill is asbestos.

8. Choose the correct statements:
Statement I: Emphysema decreases respiratory surface area.
Statement II: Fibrosis increases elasticity of the lungs.
1. Both statements are correct.
2. Both statements are incorrect.
3. Only Statement I is correct.
4. Only Statement II is correct.

In Emphysema, alveolar walls are destroyed, reducing the respiratory surface area. In contrast, Fibrosis reduces elasticity due to thickening of lung tissue. Thus, only Statement I is correct, and the answer is Option 3.

9. Which of the following disorders is allergic in nature?
1. Asthma
2. Fibrosis
3. Asbestosis
4. Emphysema

Asthma is an allergic disorder where allergens like dust, pollen, or cold air trigger inflammation of bronchi and bronchioles. This causes breathlessness and wheezing. Hence, the correct answer is Option 1 (Asthma).

10. Which disease is associated with alveolar damage and poor oxygen diffusion?
1. Emphysema
2. Bronchitis
3. Asthma
4. Fibrosis

In Emphysema, alveolar walls break down, merging small sacs into large ones, reducing surface area for gas exchange. As a result, oxygen diffusion decreases, and the patient experiences breathlessness. Therefore, the correct answer is Option 1 (Emphysema).

Topic: Pulmonary Volumes and Capacities; Subtopic: Respiratory Volumes and Their Combinations

Keyword Definitions:
• Tidal Volume (TV): Volume of air inspired or expired during normal breathing, approximately 500 mL in a healthy adult.
• Expiratory Reserve Volume (ERV): Extra air expelled after a normal expiration, around 1000–1200 mL.
• Inspiratory Reserve Volume (IRV): Maximum volume of air inspired after a normal inspiration, about 2500–3000 mL.
• Residual Volume (RV): Air remaining in lungs after maximal expiration, about 1100–1200 mL.
• Vital Capacity (VC): Total volume of air exhaled after maximum inspiration (TV + IRV + ERV).

Lead Question – 2024

Match List I with List II
List I          List II
A. Expiratory capacity     I. Expiratory reserve volume + Tidal volume + Inspiratory reserve volume
B. Functional residual capacity     II. Tidal volume + Expiratory reserve volume
C. Vital capacity     III. Tidal volume + Inspiratory reserve volume
D. Inspiratory capacity     IV. Expiratory reserve volume + Residual volume

Choose the correct answer from the options given below
(1) A-III, B-II, C-IV, D-I
(2) A-II, B-IV, C-I, D-III
(3) A-I, B-III, C-II, D-IV
(4) A-II, B-I, C-IV, D-III

Explanation: The correct answer is (2) A-II, B-IV, C-I, D-III. Expiratory capacity equals tidal volume plus expiratory reserve volume. Functional residual capacity equals expiratory reserve volume plus residual volume. Vital capacity equals tidal volume, expiratory reserve, and inspiratory reserve volumes. Inspiratory capacity equals tidal volume plus inspiratory reserve volume. These combinations help assess lung efficiency and capacity.

1. Which of the following represents the functional residual capacity of lungs?
(1) TV + IRV
(2) ERV + RV
(3) IRV + ERV
(4) TV + ERV

Explanation: The correct answer is (2) ERV + RV. Functional residual capacity represents the volume of air remaining in lungs after normal expiration. It includes expiratory reserve and residual volumes, helping prevent alveolar collapse. FRC provides a continuous gas exchange between breaths, maintaining oxygenation during short apneas or shallow breathing.

2. Vital capacity is the sum of:
(1) TV + IRV
(2) IRV + ERV
(3) TV + IRV + ERV
(4) TV + ERV + RV

Explanation: The correct answer is (3) TV + IRV + ERV. Vital capacity measures the maximum volume of air exhaled after the deepest inspiration. It reflects lung strength and elasticity. Reduced VC indicates restrictive lung disorders. It helps in evaluating respiratory health and the efficiency of ventilatory muscles during breathing.

3. Inspiratory capacity is composed of:
(1) IRV + RV
(2) IRV + ERV
(3) IRV + TV
(4) TV + ERV

Explanation: The correct answer is (3) IRV + TV. Inspiratory capacity represents the maximum air volume that can be inhaled after a normal expiration. It measures the capacity of lungs to draw in fresh air. It increases with physical training and decreases in restrictive pulmonary conditions such as fibrosis or obesity.

4. Residual volume refers to:
(1) Air expelled after maximum expiration
(2) Air remaining after normal expiration
(3) Air remaining after maximum expiration
(4) Air inhaled during normal breathing

Explanation: The correct answer is (3) Air remaining after maximum expiration. Residual volume prevents alveoli from collapsing by keeping them partially inflated. It cannot be measured directly using spirometry but is essential in maintaining constant gas exchange and stable blood oxygen levels even between successive breaths.

5. Tidal volume during quiet breathing in a normal adult is approximately:
(1) 200 mL
(2) 500 mL
(3) 800 mL
(4) 1000 mL

Explanation: The correct answer is (2) 500 mL. Tidal volume represents air inspired or expired during a normal breath. It maintains efficient alveolar ventilation. It increases during exercise and decreases in restrictive lung conditions. Tidal volume ensures constant oxygen delivery and carbon dioxide removal at rest and during mild activity.

6. Which of the following is the sum of tidal volume and expiratory reserve volume?
(1) Functional residual capacity
(2) Expiratory capacity
(3) Inspiratory capacity
(4) Vital capacity

Explanation: The correct answer is (2) Expiratory capacity. It measures the total volume of air exhaled after a normal inspiration. It combines tidal and expiratory reserve volumes and indicates the lungs’ ability to expel air effectively. It is useful in diagnosing obstructive pulmonary diseases such as asthma and bronchitis.

7. Assertion-Reason Type Question
Assertion (A): Residual volume cannot be measured by a simple spirometer.
Reason (R): Because it represents air that never leaves the lungs, even after maximum expiration.
(1) Both A and R are true, and R is the correct explanation of A
(2) Both A and R are true, but R is not the correct explanation of A
(3) A is true, R is false
(4) A is false, R is true

Explanation: The correct answer is (1). Residual volume cannot be measured by spirometry because it is the air that remains in lungs even after maximal expiration. This air ensures alveolar stability and continuous gas exchange, preventing collapse of pulmonary alveoli during forced expiration.

8. Matching Type Question
Match the following pulmonary volumes:
A. Tidal Volume     I. 1100 mL
B. Expiratory Reserve Volume     II. 500 mL
C. Residual Volume     III. 1200 mL
D. Inspiratory Reserve Volume     IV. 2500–3000 mL
(1) A-II, B-I, C-III, D-IV
(2) A-II, B-III, C-I, D-IV
(3) A-I, B-II, C-III, D-IV
(4) A-II, B-IV, C-III, D-I

Explanation: The correct answer is (1). Tidal Volume = 500 mL, Expiratory Reserve Volume = 1100 mL, Residual Volume = 1200 mL, and Inspiratory Reserve Volume = 2500–3000 mL. Each value represents a specific lung volume component critical for maintaining normal respiration and total lung capacity.

9. Fill in the Blanks Type Question
Total Lung Capacity (TLC) is equal to ________.
(1) VC + RV
(2) ERV + TV
(3) IRV + TV + ERV
(4) TV + RV

Explanation: The correct answer is (1) VC + RV. Total Lung Capacity represents the maximum volume of air lungs can hold after the deepest inspiration. It includes vital capacity and residual volume, typically around 6000 mL in adults. TLC helps evaluate restrictive and obstructive pulmonary disorders.

10. Choose the Correct Statements
Statement I: Vital capacity decreases in asthma and emphysema.
Statement II: Residual volume increases in obstructive lung diseases.
(1) Both statements are true
(2) Both statements are false
(3) Statement I is true, Statement II is false
(4) Statement I is false, Statement II is true

Explanation: The correct answer is (1). In asthma and emphysema, airflow obstruction reduces vital capacity due to incomplete exhalation, while residual volume increases as trapped air remains in lungs. These respiratory parameters are important indicators for lung function tests and disease diagnosis.

Topic: Respiratory System Physiology; Subtopic: Oxyhaemoglobin Formation and Gas Transport

Keyword Definitions:

• Oxyhaemoglobin: Compound formed when oxygen binds reversibly with haemoglobin in red blood cells under high pO2 and low pCO2 conditions.

• pO2 (Partial Pressure of Oxygen): Measure of oxygen concentration in a gas or liquid, influencing oxygen binding with haemoglobin.

• pCO2 (Partial Pressure of Carbon dioxide): Indicates the concentration of CO2; lower pCO2 favors oxygen binding in lungs.

• H+ Concentration: Determines acidity; lower H+ concentration (higher pH) promotes oxyhaemoglobin formation.

• Haemoglobin: Iron-containing respiratory pigment in red blood cells that carries oxygen and carbon dioxide.

Lead Question (2024)

Which of the following factors are favourable for the formation of oxyhaemoglobin in alveoli?
(1) High pO2 and Lesser H+ concentration
(2) Low pCO2 and High H+ concentration
(3) Low pCO2 and High temperature
(4) High pO2 and High pCO2

Explanation: The correct answer is (1) High pO2 and Lesser H+ concentration. In alveoli, oxygen binds efficiently to haemoglobin when oxygen tension is high, carbon dioxide tension is low, temperature is moderate, and the environment is slightly alkaline (low H+). These conditions shift the oxygen-haemoglobin dissociation curve to the left, favoring oxyhaemoglobin formation.

1. Which factor promotes dissociation of oxyhaemoglobin at the tissue level?
(1) High pO2
(2) Low pCO2
(3) High pCO2 and High H+
(4) Low temperature
Explanation: The correct answer is (3) High pCO2 and High H+. At the tissue level, high CO2 and acidity lower haemoglobin’s affinity for oxygen, promoting oxygen release for cellular respiration. This phenomenon, known as the Bohr effect, facilitates efficient oxygen unloading where it is most needed.

2. Which of the following best describes the Bohr effect?
(1) Increase in oxygen binding due to high CO2
(2) Decrease in oxygen binding due to high CO2 and H+
(3) Increase in CO2 binding due to high O2
(4) Oxygen binding independent of CO2
Explanation: The correct answer is (2). The Bohr effect states that increased carbon dioxide concentration and acidity reduce haemoglobin’s affinity for oxygen. This aids in oxygen release to active tissues where CO2 levels are high, ensuring proper gas exchange and cellular respiration efficiency.

3. What happens to haemoglobin at the tissue level where pO2 is low?
(1) It forms oxyhaemoglobin
(2) It releases oxygen
(3) It becomes more alkaline
(4) It binds with more oxygen
Explanation: The correct answer is (2) It releases oxygen. In tissues, oxygen concentration is low and carbon dioxide concentration is high, causing haemoglobin to release oxygen. This ensures proper oxygen delivery to body cells for metabolic processes, maintaining efficient cellular energy production.

4. Assertion-Reason Type:
Assertion (A): High temperature in tissues helps in oxygen release from oxyhaemoglobin.
Reason (R): Oxygen binding to haemoglobin is favored by high temperature.
(1) Both A and R are true and R is correct explanation of A.
(2) Both A and R are true but R is not correct explanation of A.
(3) A is true but R is false.
(4) Both A and R are false.
Explanation: The correct answer is (3). Higher temperature in active tissues weakens the haemoglobin-oxygen bond, facilitating oxygen release. However, oxygen binding is favored by low temperature, not high. This thermally induced dissociation supports metabolic activity during exercise or fever.

5. Matching Type:
Match the following conditions with their effects on haemoglobin:
A. High pO2 — (i) Favors oxyhaemoglobin formation
B. High pCO2 — (ii) Promotes oxygen dissociation
C. High temperature — (iii) Decreases oxygen affinity
(1) A-i, B-ii, C-iii
(2) A-ii, B-i, C-iii
(3) A-iii, B-ii, C-i
(4) A-i, B-iii, C-ii
Explanation: The correct answer is (1). High oxygen pressure favors oxyhaemoglobin formation, while elevated CO2 and temperature promote oxygen release. This combination of factors ensures oxygen binds in the lungs and is released effectively in tissues requiring energy.

6. Fill in the Blanks:
Oxygen dissociation from oxyhaemoglobin is enhanced by ________.
(1) Low pCO2 and Low temperature
(2) High pCO2 and High H+ concentration
(3) High pO2 and Low H+ concentration
(4) Low temperature and Low H+
Explanation: The correct answer is (2) High pCO2 and High H+ concentration. In metabolically active tissues, CO2 and acidity increase, shifting the dissociation curve rightward, promoting oxygen unloading. This physiological adaptation ensures oxygen supply meets tissue demand.

7. Choose the correct statements:
Statement I: Low pCO2 favors oxyhaemoglobin formation.
Statement II: High temperature favors oxyhaemoglobin dissociation.
(1) Both statements are true.
(2) Only Statement I is true.
(3) Only Statement II is true.
(4) Both statements are false.
Explanation: The correct answer is (1). Low carbon dioxide tension promotes oxygen binding in lungs, while elevated temperature enhances oxygen release in tissues. These contrasting conditions ensure proper gas exchange and efficient transport of respiratory gases throughout the body.

8. The oxygen-haemoglobin dissociation curve is shifted to the right by:
(1) Decreased CO2 concentration
(2) Increased temperature and acidity
(3) Low H+ concentration
(4) Decreased temperature
Explanation: The correct answer is (2). Increased temperature, pCO2, and acidity shift the curve rightward, decreasing oxygen affinity and promoting oxygen release. This adaptive response supports active tissue metabolism where oxygen demand is elevated during exercise or stress.

9. Which statement correctly explains the effect of pH on haemoglobin-oxygen binding?
(1) High pH decreases oxygen binding
(2) Low pH enhances oxygen binding
(3) High pH promotes oxygen binding
(4) pH has no effect on oxygen binding
Explanation: The correct answer is (3). A high pH (low H+) environment increases haemoglobin’s affinity for oxygen, promoting oxyhaemoglobin formation in lungs. In contrast, low pH reduces oxygen affinity, ensuring oxygen release to acidic, metabolically active tissues.

10. Which of the following conditions in alveoli favors oxygen loading?
(1) High pO2, Low pCO2, Low temperature
(2) Low pO2, High pCO2, High temperature
(3) High pCO2, High temperature
(4) Low pO2, Low pCO2
Explanation: The correct answer is (1). In alveoli, high oxygen tension, low carbon dioxide levels, and cooler temperature enhance oxygen binding with haemoglobin. These conditions optimize oxygen loading into blood for transport to tissues throughout the body.

Topic: Respiratory System; Subtopic: High Altitude Physiology and Adaptation

Keyword Definitions:

• Altitude Sickness: A condition caused by rapid exposure to low oxygen at high altitudes.

• Atmospheric pressure: The pressure exerted by the weight of air in the atmosphere.

• Hypoxia: Deficiency of oxygen in tissues.

• High altitude: Elevation above 2,500 meters (8,200 feet) where oxygen availability decreases.

• Respiration: The process of gas exchange between body and environment.

• Heart palpitations: Rapid or irregular heartbeat.

• Breathing difficulty: Shortness of breath or dyspnea due to low oxygen.

• Acclimatization: Physiological adaptation to high-altitude conditions.

• Erythropoiesis: Production of red blood cells, often increased at high altitude.

• Oxygen saturation: The percentage of hemoglobin bound with oxygen in blood.

• Barometric pressure: Pressure exerted by the atmosphere, decreasing with altitude.

Lead Question - 2023 (Manipur)

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R)

Assertion (A): A person goes to high altitude and experiences "Altitude Sickness" with symptoms like breathing difficulty and heart palpitations.

Reason (R): Due to low atmospheric pressure at high altitude, the body does not get sufficient oxygen.

In the light of the above statements, choose the correct answer from the options given below:

1. (A) is True but (R) is False

2. (A) is False but (R) is True

3. Both (A) and (R) are True and (R) is the correct explanation of (A)

4. Both (A) and (R) are True but (R) is not the correct explanation of (A)

Explanation:

Altitude sickness occurs when a person rapidly ascends to high elevations where the atmospheric pressure is lower. This reduction decreases the partial pressure of oxygen, leading to hypoxia. As a result, symptoms like breathlessness, dizziness, headache, and heart palpitations appear. The Assertion correctly describes these symptoms, and the Reason correctly explains that low atmospheric pressure reduces oxygen availability, which is the cause. Hence, both statements are true, and the Reason is the correct explanation of the Assertion. Correct answer is 3.

1. Single Correct Answer MCQ:

Which physiological response helps acclimatization to high altitude?

1. Decreased heart rate

2. Increased erythropoiesis

3. Reduced breathing rate

4. Vasoconstriction in lungs

Explanation:

At high altitude, the body adapts by increasing erythropoiesis, which raises red blood cell count to improve oxygen carrying capacity. Heart rate and breathing rate increase to compensate, and vasodilation occurs in tissues. Correct answer is 2.

2. Single Correct Answer MCQ:

Low atmospheric pressure at high altitude primarily reduces:

1. Blood flow

2. Oxygen partial pressure

3. Carbon dioxide levels

4. Nitrogen levels

Explanation:

As altitude increases, atmospheric pressure decreases, lowering the partial pressure of oxygen. This limits the amount of oxygen diffused into blood, causing hypoxia. Correct answer is 2.

3. Single Correct Answer MCQ:

Which symptom is NOT commonly associated with altitude sickness?

1. Nausea

2. Headache

3. Heart palpitations

4. Increased appetite

Explanation:

Altitude sickness symptoms include headache, dizziness, nausea, vomiting, breathlessness, and heart palpitations. Increased appetite is not typically associated with this condition. Correct answer is 4.

4. Single Correct Answer MCQ:

Acclimatization includes which of the following adaptations?

1. Decreased hemoglobin concentration

2. Increased respiratory rate

3. Lowered red blood cell production

4. Reduced capillary density

Explanation:

Acclimatization involves increased respiratory rate, higher red blood cell production, and increased hemoglobin concentration to enhance oxygen delivery. Correct answer is 2.

5. Single Correct Answer MCQ:

The main cause of altitude sickness is:

1. Cold temperature

2. Low oxygen availability

3. High humidity

4. Excess carbon dioxide

Explanation:

Altitude sickness is caused by hypoxia due to low oxygen availability at high altitude, which results from reduced atmospheric pressure. Correct answer is 2.

6. Single Correct Answer MCQ:

Which hormone increases to stimulate red blood cell production at high altitude?

1. Insulin

2. Erythropoietin

3. Cortisol

4. Adrenaline

Explanation:

Erythropoietin secretion rises at high altitude, stimulating bone marrow to produce more red blood cells, enhancing oxygen transport to tissues. Correct answer is 2.

7. Assertion-Reason MCQ:

Assertion (A): Hyperventilation occurs during altitude sickness.

Reason (R): Low oxygen levels in blood trigger increased respiratory rate.

1. Both A and R are true and R explains A

2. Both A and R are true but R does not explain A

3. A is true but R is false

4. Both A and R are false

Explanation:

Hyperventilation is a compensatory mechanism to increase oxygen intake when blood oxygen is low. Both Assertion and Reason are true, and the Reason correctly explains the Assertion. Correct answer is 1.

8. Matching Type MCQ:

Match the symptom with its physiological cause:

A. Breathlessness — (i) Low oxygen saturation

B. Heart palpitations — (ii) Hypoxia-induced tachycardia

C. Headache — (iii) Cerebral hypoxia

D. Nausea — (iv) Gastrointestinal response to hypoxia

1. A-(i), B-(ii), C-(iii), D-(iv)

2. A-(ii), B-(i), C-(iv), D-(iii)

3. A-(i), B-(iv), C-(ii), D-(iii)

4. A-(iii), B-(ii), C-(i), D-(iv)

Explanation:

Breathlessness arises due to low oxygen saturation, heart palpitations due to hypoxia-induced tachycardia, headache due to cerebral hypoxia, and nausea due to gastrointestinal response to low oxygen. Correct matching is 1.

9. Fill in the Blanks MCQ:

At high altitude, oxygen availability _______ and erythropoiesis _______.

1. Increases, decreases

2. Decreases, increases

3. Remains same, remains same

4. Decreases, decreases

Explanation:

With increasing altitude, oxygen partial pressure decreases, leading to hypoxia. The body compensates by increasing erythropoiesis to raise red blood cell count, improving oxygen delivery. Correct answer is 2.

10. Choose the correct statements MCQ:

Statement I: Low atmospheric pressure reduces oxygen diffusion into blood.

Statement II: Altitude sickness symptoms appear immediately in all individuals.

1. Statement I only

2. Statement II only

3. Both statements are true

4. Both statements are false

Explanation:

Low atmospheric pressure reduces oxygen diffusion, causing hypoxia, which can trigger altitude sickness. However, symptoms vary and may take hours or days to appear. Statement I is correct; Statement II is incorrect. Correct answer is 1.

Topic: Mechanism of Respiration; Subtopic: Sequence and Process of Gaseous Exchange

Keyword Definitions:

• Pulmonary Ventilation: The process of breathing where air is drawn into and expelled from the lungs.

• Alveolar Membrane: Thin barrier between alveolar air and blood capillaries where exchange of O2 and CO2 occurs.

• Gas Transport: The movement of O2 and CO2 in the blood via hemoglobin and plasma.

• Cellular Respiration: Utilisation of oxygen by cells to oxidize organic molecules, releasing energy and CO2.

• Diffusion: Passive movement of gases from higher to lower concentration across biological membranes.

Lead Question – 2023 (Manipur)

Select the sequence of steps in respiration.
(A) Diffusion of gases (O2 and CO2) across alveolar membrane.
(B) Diffusion of O2 and CO2 between blood and tissues.
(C) Transport of gases by the blood.
(D) Pulmonary ventilation by which atmospheric air is drawn in and CO2-rich alveolar air is released out.
(E) Utilisation of O2 by the cells for catabolic reactions and resultant release of CO2.

Choose the correct answer from the options given below:
1. (D), (A), (C), (B), (E)
2. (C), (B), (A), (E), (D)
3. (B), (C), (E), (D), (A)
4. (A), (C), (B), (E), (D)

Explanation: The correct answer is (1) (D), (A), (C), (B), (E). Respiration begins with pulmonary ventilation, followed by diffusion of gases through alveoli. Oxygen and carbon dioxide are transported via blood, exchanged at tissues, and finally utilized in cellular respiration for energy production. This sequence ensures efficient oxygen delivery and carbon dioxide removal for metabolism.

Guessed Question 1: In human respiration, the exchange of gases between alveoli and blood takes place by:
1. Active transport
2. Osmosis
3. Diffusion
4. Filtration
Explanation: The correct answer is Diffusion. The exchange of O2 and CO2 across alveolar and capillary membranes occurs by simple diffusion due to partial pressure differences. Oxygen diffuses from alveolar air to blood, while CO2 moves from blood to alveoli, ensuring proper gas exchange during breathing.

Guessed Question 2: Which one of the following has the highest affinity for oxygen?
1. Myoglobin
2. Hemoglobin
3. Plasma
4. Red Blood Cells
Explanation: The correct answer is Myoglobin. Myoglobin, present in muscle cells, binds oxygen more tightly than hemoglobin, serving as an oxygen reserve for muscle activity. Its high affinity helps maintain oxygen supply during intense exercise when oxygen availability decreases in the bloodstream.

Guessed Question 3: The respiratory pigment in human blood is:
1. Chlorocruorin
2. Hemocyanin
3. Hemoglobin
4. Hemerythrin
Explanation: The correct answer is Hemoglobin. It is an iron-containing protein present in red blood cells responsible for oxygen transport. Hemoglobin binds oxygen in the lungs to form oxyhemoglobin and releases it in tissues, ensuring efficient respiration. Other pigments occur in non-human species like annelids and mollusks.

Guessed Question 4: The respiratory surface in humans is formed by:
1. Bronchioles
2. Alveoli
3. Trachea
4. Bronchi
Explanation: The correct answer is Alveoli. Alveoli are tiny air sacs at the end of bronchioles providing a large surface area for gaseous exchange. They are lined by a thin epithelial membrane facilitating diffusion of oxygen into blood and carbon dioxide out of blood during breathing.

Guessed Question 5: Which of the following processes is also called internal respiration?
1. Exchange of gases in lungs
2. Utilisation of O2 by cells
3. Transport of O2 by blood
4. Diffusion across alveolar membrane
Explanation: The correct answer is Utilisation of O2 by cells. Internal respiration refers to cellular respiration, where oxygen is used to oxidize glucose producing energy, water, and CO2. It is distinct from external respiration, which involves gas exchange between lungs and external environment.

Guessed Question 6: During expiration, the diaphragm:
1. Contracts
2. Relaxes
3. Remains flat
4. Moves downward
Explanation: The correct answer is Relaxes. During expiration, diaphragm muscles relax and move upward into a dome shape, decreasing thoracic cavity volume. This increases pressure inside the lungs, causing air rich in CO2 to move out, completing the exhalation process efficiently.

Guessed Question 7 (Assertion–Reason Type):
Assertion (A): Oxygen transport in blood occurs mainly by hemoglobin.
Reason (R): Each hemoglobin molecule can carry a maximum of four molecules of oxygen.
1. (A) and (R) are true and (R) is the correct explanation of (A).
2. (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true, (R) is false.
4. (A) is false, (R) is true.
Explanation: The correct answer is Option 1. Oxygen is primarily transported by hemoglobin, forming oxyhemoglobin in lungs. Each hemoglobin molecule has four heme groups, each binding one oxygen molecule. Thus, four oxygen molecules can be carried per hemoglobin, making (R) the correct explanation for (A).

Guessed Question 8 (Matching Type):
Match the following respiratory structures with their functions:
A. Alveoli — (i) Transport of gases
B. Trachea — (ii) Passage of air
C. Hemoglobin — (iii) Oxygen transport
D. Diaphragm — (iv) Pulmonary ventilation

1. A–i, B–ii, C–iii, D–iv
2. A–ii, B–iii, C–iv, D–i
3. A–iv, B–i, C–ii, D–iii
4. A–iii, B–ii, C–i, D–iv
Explanation: The correct answer is 1. A–i, B–ii, C–iii, D–iv. Alveoli facilitate gas exchange, trachea conducts air, hemoglobin transports oxygen, and diaphragm aids in breathing movements. Together, these components ensure smooth functioning of the respiratory system maintaining oxygen and carbon dioxide balance.

Guessed Question 9 (Fill in the Blanks):
______ is the volume of air inspired or expired during normal breathing.
1. Vital capacity
2. Tidal volume
3. Residual volume
4. Expiratory reserve volume
Explanation: The correct answer is Tidal volume. It represents the amount of air (about 500 mL in an adult) inhaled or exhaled in a normal respiratory cycle. This volume ensures sufficient oxygen intake and carbon dioxide elimination during quiet breathing, maintaining efficient gas exchange.

Guessed Question 10 (Choose the Correct Statements):
Statement I: The exchange of gases in lungs occurs by diffusion.
Statement II: The diffusion rate depends on partial pressure gradients of gases.
1. Both statements are true.
2. Both statements are false.
3. Only Statement I is true.
4. Only Statement II is true.
Explanation: The correct answer is 1. Both statements are true. Gas exchange across alveolar membranes occurs by simple diffusion, driven by differences in partial pressures of O2 and CO2 between alveolar air and blood. This principle ensures effective respiration and oxygen supply to body tissues.

Topic: Respiratory System; Subtopic: Lung Volumes and Capacities

Lead Question - 2023

Vital capacity of lung is _________
(1) IRV + ERV + TV – RV
(2) IRV + ERV + TV
(3) IRV + ERV
(4) IRV + ERV + TV + RV

Answer: (2) IRV + ERV + TV. Vital capacity (VC) is the maximum volume of air a person can expel from the lungs after a maximum inhalation. It includes tidal volume (TV), inspiratory reserve volume (IRV), and expiratory reserve volume (ERV). Residual volume (RV) is not included in VC as it represents air remaining in lungs after maximal exhalation. Measurement of VC helps assess pulmonary function and diagnose respiratory disorders like restrictive or obstructive lung diseases. Regular breathing exercises can improve VC by enhancing lung elasticity and increasing total air exchange efficiency over time.

Keyword Definitions:

• Vital Capacity (VC): The maximum volume of air expelled from lungs after maximal inhalation, calculated as IRV + ERV + TV.

• Tidal Volume (TV): Air volume inhaled or exhaled during normal breathing.

• Inspiratory Reserve Volume (IRV): Additional air that can be inhaled after normal inspiration.

• Expiratory Reserve Volume (ERV): Additional air that can be exhaled after normal expiration.

• Residual Volume (RV): Air remaining in lungs after maximal exhalation, not included in VC.

• Lung capacities: Combination of lung volumes that reflect respiratory function.

• Respiratory system: Organs and structures involved in gas exchange.

1. Single Correct Answer:

Which volume represents air remaining in lungs after maximal exhalation?
(1) Tidal volume
(2) Residual volume
(3) Inspiratory reserve volume
(4) Expiratory reserve volume

Answer: (2) Residual volume. RV prevents lung collapse and maintains continuous gas exchange even after maximum exhalation, ensuring oxygen supply between breaths.

2. Single Correct Answer:

Maximum air that can be inhaled after normal inspiration is called?
(1) IRV
(2) ERV
(3) TV
(4) RV

Answer: (1) IRV. Inspiratory reserve volume represents the additional air a person can inhale beyond normal tidal inspiration, important in calculating vital capacity.

3. Single Correct Answer:

Which combination gives Total Lung Capacity (TLC)?
(1) VC + RV
(2) TV + IRV + ERV
(3) IRV + ERV
(4) VC only

Answer: (1) VC + RV. Total lung capacity includes vital capacity plus residual volume, representing total volume of air lungs can hold after maximal inhalation.

4. Single Correct Answer:

Which lung capacity is decreased in restrictive lung diseases?
(1) Vital capacity
(2) Residual volume
(3) Expiratory reserve volume
(4) Tidal volume

Answer: (1) Vital capacity. Restrictive lung diseases reduce lung compliance and expandability, decreasing the maximum air volume exchanged, which is reflected in reduced VC.

5. Single Correct Answer:

Normal air inhaled or exhaled during quiet breathing is?
(1) TV
(2) IRV
(3) ERV
(4) RV

Answer: (1) Tidal volume. TV is the volume of air moved during normal, restful breathing, essential for baseline gas exchange and pulmonary ventilation.

6. Single Correct Answer:

Which lung volume can be directly measured using spirometry?
(1) RV
(2) TV
(3) TLC
(4) FRC

Answer: (2) TV. Spirometry measures tidal volume, inspiratory and expiratory volumes, but residual volume and total lung capacity require indirect methods.

7. Assertion-Reason:

Assertion A: Vital capacity is a measure of maximum air exchange.
Reason R: VC includes TV, IRV, and ERV.
Options:
(1) A true, R false
(2) A false, R true
(3) Both true, R explains A
(4) Both true, R does not explain A

Answer: (3) Both true, R explains A. VC quantifies the maximum volume of air exhaled after full inhalation, summing tidal, inspiratory reserve, and expiratory reserve volumes.

8. Matching Type:

Match the lung volume with its description:
List I | List II
A. IRV | I. Normal inhalation
B. ERV | II. Maximal exhalation
C. TV | III. Additional inhalation beyond TV
D. RV | IV. Air remaining after maximal exhalation
Options:
(1) A-III, B-II, C-I, D-IV
(2) A-I, B-II, C-III, D-IV
(3) A-II, B-III, C-I, D-IV
(4) A-III, B-I, C-II, D-IV

Answer: (1) A-III, B-II, C-I, D-IV. IRV is extra inhalation, ERV is additional exhalation, TV is normal breath, RV is residual air.

9. Fill in the Blanks:

The sum of tidal volume, inspiratory reserve volume, and expiratory reserve volume is called _______.
Options: (1) TLC (2) VC (3) RV (4) FRC

Answer: (2) VC. Vital capacity represents the maximum exhaled air after a full inhalation, essential for assessing pulmonary function.

10. Choose the correct statements:

Statement I: Residual volume is included in vital capacity.
Statement II: Vital capacity can be increased with breathing exercises.
Options:
(1) Only I is correct
(2) Only II is correct
(3) Both I and II are correct
(4) Both I and II are incorrect

Answer: (2) Only II is correct. Residual volume is not included in VC, but regular exercises can enhance lung expansion, increasing vital capacity over time.

Chapter: Breathing and Exchange of Gases; Topic: Neural Regulation of Respiration; Subtopic: Respiratory Centers of Brain

Keyword Definitions:
• Pneumotaxic Centre: A neural centre in the pons that regulates breathing rhythm by reducing inspiration duration.
• Medulla Oblongata: The part of the brainstem that controls vital reflexes like heart rate and respiration.
• Pons: The part of the brainstem connecting medulla and midbrain, containing pneumotaxic centre.
• Thalamus: A sensory relay centre in the forebrain, not involved in respiration control.
• Cerebrum: Controls voluntary actions and higher thought processes.

Lead Question - 2022 (Ganganagar)

Identify the region of human brain which has pneumotaxic centre that alters respiratory rate by reducing the duration of inspiration.

1. Medulla
2. Pons
3. Thalamus
4. Cerebrum

Explanation: The correct answer is option 2 (Pons). The pneumotaxic centre is located in the pons region of the brainstem. It regulates breathing rhythm by controlling the switch-off point of inspiration. By reducing the duration of inspiration, it increases the rate of breathing. The medulla contains inspiratory and expiratory centres, not pneumotaxic control.

1. Which part of the brain primarily regulates the basic rhythm of respiration?
1. Medulla oblongata
2. Cerebrum
3. Hypothalamus
4. Cerebellum

Explanation: The correct answer is medulla oblongata. The medullary respiratory centre contains inspiratory and expiratory neurons that generate the basic rhythm of breathing. It automatically controls the respiratory muscles. The cerebrum and hypothalamus can influence but not directly generate the rhythm of respiration.

2. The apneustic centre present in the pons is responsible for:
1. Promoting inspiration
2. Inhibiting inspiration
3. Controlling heart rate
4. Regulating blood pressure

Explanation: The correct answer is promoting inspiration. The apneustic centre in the lower pons stimulates the inspiratory centre in the medulla, prolonging inspiration. Its action is balanced by the pneumotaxic centre, which inhibits inspiration, ensuring normal rhythmic breathing.

3. The chemoreceptors that regulate respiration are located in:
1. Aorta and carotid arteries
2. Cerebellum
3. Pons
4. Thalamus

Explanation: The correct answer is aorta and carotid arteries. These peripheral chemoreceptors detect changes in CO₂, O₂, and pH levels of blood. Increased CO₂ or decreased pH stimulates these receptors, which signal the medullary respiratory centre to increase the breathing rate.

4. Which of the following is responsible for voluntary control of breathing?
1. Cerebrum
2. Pons
3. Medulla oblongata
4. Hypothalamus

Explanation: The correct answer is cerebrum. The cerebrum allows voluntary control of respiration during activities like talking, singing, or breath-holding. However, involuntary rhythmic breathing is maintained by the medulla and pons even when conscious control ceases.

5. Which nerve transmits impulses from chemoreceptors to the brain for respiration control?
1. Vagus nerve
2. Sciatic nerve
3. Optic nerve
4. Facial nerve

Explanation: The correct answer is vagus nerve. The vagus nerve carries sensory impulses from peripheral chemoreceptors and baroreceptors to the medulla. It plays an important role in adjusting respiratory rate in response to blood gas levels and maintaining homeostasis.

6. Which part of the brain controls the rhythmic contraction of the diaphragm?
1. Medulla oblongata
2. Pons
3. Cerebrum
4. Midbrain

Explanation: The correct answer is medulla oblongata. The medullary respiratory centre sends rhythmic impulses to the phrenic nerve, which stimulates the diaphragm for inspiration. It ensures automatic, rhythmic contraction of respiratory muscles necessary for breathing.

7. Assertion-Reason Question:
Assertion (A): Pneumotaxic centre decreases the duration of inspiration.
Reason (R): It sends inhibitory signals to the inspiratory centre in the medulla.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, R is false.
4. A is false, R is true.

Explanation: The correct answer is option 1. The pneumotaxic centre in the pons sends inhibitory signals to the inspiratory centre in the medulla. This limits inspiration duration, thus controlling breathing frequency. Hence, both the assertion and reason are true, and the reason correctly explains the assertion.

8. Matching Type:
Match the following respiratory centres with their functions:
(a) Inspiratory centre - (i) Promotes inhalation
(b) Pneumotaxic centre - (ii) Inhibits inspiration
(c) Apneustic centre - (iii) Prolongs inspiration

1. (a)-(i), (b)-(ii), (c)-(iii)
2. (a)-(iii), (b)-(ii), (c)-(i)
3. (a)-(ii), (b)-(i), (c)-(iii)
4. (a)-(i), (b)-(iii), (c)-(ii)

Explanation: The correct answer is option 1. The inspiratory centre promotes inhalation, pneumotaxic centre inhibits it, and apneustic centre prolongs it. These centres coordinate to maintain smooth respiratory rhythm. Any imbalance can lead to irregular breathing patterns.

9. Fill in the Blanks:
The respiratory rhythm centre that generates basic breathing rhythm is located in the ________.

1. Cerebellum
2. Medulla oblongata
3. Hypothalamus
4. Pons

Explanation: The correct answer is medulla oblongata. It contains the dorsal and ventral respiratory groups responsible for rhythmic inspiration and expiration. The centre operates automatically, maintaining respiratory rhythm even without conscious control.

10. Choose the Correct Statements:
Statement I: Pneumotaxic centre facilitates longer inspiration.
Statement II: Apneustic centre prolongs inspiration duration.

1. Both statements are true
2. Both statements are false
3. Statement I true, Statement II false
4. Statement I false, Statement II true

Explanation: The correct answer is option 4. Pneumotaxic centre shortens inspiration, while the apneustic centre prolongs it. Together, they balance breathing rhythm, ensuring proper ventilation. This coordination prevents over-inflation or insufficient expansion of lungs during breathing.

Topic: Respiratory System; Subtopic: Lung Volumes and Capacities

Keyword Definitions:

• Vital Capacity (VC): Maximum volume of air a person can exhale after a maximal inhalation, sum of IRV, TV, and ERV.

• Tidal Volume (TV): Volume of air inspired or expired during normal breathing.

• Inspiratory Reserve Volume (IRV): Extra air inhaled during a deep breath after normal inspiration.

• Expiratory Reserve Volume (ERV): Extra air exhaled after a normal expiration.

• Residual Volume (RV): Air remaining in lungs after maximal expiration, cannot be measured directly.

• Lung Capacity: Combination of two or more lung volumes.

• Total Lung Capacity (TLC): Sum of all lung volumes including RV.

• Respiratory physiology: Study of breathing, gas exchange, and lung function.

• Forced expiration: Exhalation after maximal inhalation.

• Forced inspiration: Inhalation beyond normal tidal volume.

• Pulmonary function test: Measurement of lung volumes and capacities to assess function.

Lead Question - 2022 (Ganganagar)

Which of the following statements are correct with respect to vital capacity?

(a) It includes ERV, TV and IRV

(b) Total volume of air a person can inspire after a normal expiration

(c) The maximum volume of air a person can breathe in after forced expiration

(d) It includes ERV, RV and IRV

(e) The maximum volume of air a person can breathe out after a forced inspiration

Choose the most appropriate answer from the options given below:

1. (b), (d) and (e)

2. (a), (c) and (d)

3. (a), (c) and (e)

4. (a) and (e)

Explanation: Vital capacity (VC) is the maximum volume of air a person can exhale after a maximal inhalation. It is the sum of inspiratory reserve volume (IRV), tidal volume (TV), and expiratory reserve volume (ERV). Residual volume (RV) is not included in VC. Therefore, statements (a), (c), and (e) correctly describe VC, while statements (b) and (d) are incorrect. VC reflects lung efficiency and is measured during pulmonary function tests using spirometry. Correct answer is 3.

1. Single Correct Answer MCQ:

Which of the following volumes is not included in vital capacity?

a) IRV

b) TV

c) ERV

d) RV

Explanation: Residual volume (RV) is the air remaining in the lungs after maximal exhalation and is not part of vital capacity, which only includes IRV, TV, and ERV. Correct answer is d.

2. Single Correct Answer MCQ:

Tidal volume (TV) refers to:

a) Air inspired or expired during normal breathing

b) Maximum air exhaled after deep inspiration

c) Extra air inhaled beyond normal inspiration

d) Air left in lungs after expiration

Explanation: Tidal volume (TV) is the volume of air exchanged in normal, quiet breathing. IRV and ERV correspond to extra inhaled or exhaled air. Correct answer is a.

3. Single Correct Answer MCQ:

Expiratory reserve volume (ERV) is:

a) Air inspired during forced inspiration

b) Air exhaled after normal expiration

c) Air exhaled after maximal exhalation

d) Air left in lungs after forced expiration

Explanation: ERV is the extra air that can be exhaled after normal expiration, forming part of vital capacity along with IRV and TV. Correct answer is b.

4. Single Correct Answer MCQ:

Which instrument measures vital capacity?

a) Stethoscope

b) Spirometer

c) Sphygmomanometer

d) Peak flow meter

Explanation: A spirometer measures lung volumes and capacities, including vital capacity, by recording inhaled and exhaled air. Correct answer is b.

5. Single Correct Answer MCQ:

Maximum volume of air a person can breathe in after forced expiration is:

a) Tidal volume

b) Inspiratory capacity

c) Vital capacity

d) Residual volume

Explanation: Vital capacity is the maximum volume of air inhaled after a maximal exhalation, including IRV, TV, and ERV. Correct answer is c.

6. Single Correct Answer MCQ:

Which combination represents vital capacity?

a) IRV + TV + ERV

b) IRV + TV + RV

c) TV + ERV + RV

d) IRV + RV + TLC

Explanation: Vital capacity is the sum of IRV, TV, and ERV. Residual volume (RV) is excluded. Correct answer is a.

7. Assertion-Reason MCQ:

Assertion (A): Vital capacity includes tidal, inspiratory, and expiratory volumes.

Reason (R): Vital capacity also includes residual volume.

a) Both A and R true, R explains A

b) Both A and R true, R does not explain A

c) A true, R false

d) Both false

Explanation: Assertion is true; VC includes IRV, TV, and ERV. Reason is false because RV is not part of VC. Correct answer is c.

8. Matching Type MCQ:

Match List-I with List-II:

List-I | List-II

(a) VC | (i) IRV + TV + ERV

(b) TLC | (ii) VC + RV

(c) TV | (iii) Normal breath volume

(d) RV | (iv) Air left after maximal exhalation

Options:

1. a-i, b-ii, c-iii, d-iv

2. a-ii, b-i, c-iv, d-iii

3. a-iii, b-iv, c-i, d-ii

4. a-iv, b-iii, c-ii, d-i

Explanation: Correct matches: VC (i), TLC (ii), TV (iii), RV (iv). Correct answer is 1.

9. Fill in the Blanks / Completion MCQ:

The maximum volume of air a person can exhale after a maximal inhalation is _______.

a) Tidal volume

b) Vital capacity

c) Residual volume

d) Total lung capacity

Explanation: Vital capacity represents the maximal exhaled volume after full inspiration, combining IRV, TV, and ERV. Correct answer is b.

10. Choose the correct statements MCQ (Statement I & II):

Statement I: Vital capacity includes IRV, TV, and ERV.

Statement II: Vital capacity includes residual volume.

a) Both I and II correct

b) Only I correct

c) Only II correct

d) Both incorrect

Explanation: Statement I is correct as VC includes IRV, TV, and ERV. Statement II is incorrect; residual volume is excluded from VC. Correct answer is b. 

Topic: Respiratory System; Subtopic: Neural Regulation of Respiration

Keyword Definitions:

• Chemosensitive area: Region near the medullary respiratory center sensitive to chemical changes in blood, regulating respiration rate.

• Rhythm center: Medullary respiratory center that generates the basic rhythm of breathing.

• Medulla: Part of the brainstem that contains centers controlling involuntary functions, including respiration and cardiovascular activity.

• CO2: Carbon dioxide, a byproduct of cellular respiration, detected by chemoreceptors to modulate breathing.

• O2: Oxygen, essential for cellular respiration, monitored by peripheral chemoreceptors for hypoxia detection.

• HCO3-: Bicarbonate ion, a buffer in blood that indirectly influences respiratory rate by affecting pH.

• N2: Nitrogen, an inert gas, does not significantly affect chemosensitive respiratory regulation.

• Peripheral chemoreceptors: Receptors in carotid and aortic bodies that detect O2, CO2, and pH changes.

• Respiratory control: Neural and chemical mechanisms maintaining homeostasis of blood gases.

• Homeostasis: Physiological maintenance of stable internal conditions, including blood gases.

• pH regulation: Control of hydrogen ion concentration in blood, influencing respiratory rate via central and peripheral chemoreceptors.

Lead Question - 2022 (Abroad)

In the regulation of respiration, a chemosensitive area adjacent to the rhythm centre in the medulla region of the brain, is highly sensitive to:

1. HCO3-

2. CO2

3. O2

4. N2

Explanation: The chemosensitive area near the medullary rhythm center detects changes in CO2 levels in arterial blood. Elevated CO2 increases H+ concentration, lowering pH, which stimulates the central chemoreceptors to increase the rate and depth of respiration. This mechanism maintains homeostasis of blood gases. O2 is monitored mainly by peripheral chemoreceptors, HCO3- indirectly influences pH, and N2 has negligible effect. Proper function of this area is vital for normal respiratory control and acid-base balance. Correct answer: 2

1. SINGLE CORRECT ANSWER MCQ

Which gas primarily stimulates central chemoreceptors in the medulla to control breathing?

1. O2

2. CO2

3. HCO3-

4. N2

Explanation: Central chemoreceptors in the medulla respond primarily to CO2 levels. CO2 diffuses into cerebrospinal fluid, forming H+ ions that lower pH and trigger increased respiration. O2 is mainly detected by peripheral chemoreceptors, HCO3- indirectly affects pH, and N2 is physiologically inert. This feedback system is crucial for maintaining acid-base balance and normal respiratory rate. Correct answer: 2

2. SINGLE CORRECT ANSWER MCQ

Peripheral chemoreceptors primarily monitor:

1. CO2

2. O2

3. HCO3-

4. N2

Explanation: Peripheral chemoreceptors in carotid and aortic bodies respond mainly to hypoxia (low O2) in arterial blood. They also respond to CO2 and pH changes to a lesser degree. HCO3- indirectly affects chemoreceptor activity, and N2 does not stimulate them. These receptors provide rapid feedback to adjust respiration rate and maintain oxygen homeostasis. Correct answer: 2

3. SINGLE CORRECT ANSWER MCQ

An increase in arterial CO2 leads to:

1. Decreased respiratory rate

2. Increased respiratory rate

3. No change in breathing

4. Only peripheral vasodilation

Explanation: Elevated arterial CO2 increases H+ concentration, stimulating central chemoreceptors in the medulla. This triggers an increase in both rate and depth of respiration, enhancing CO2 removal and restoring pH. Peripheral chemoreceptors contribute minimally, and N2 does not affect breathing. This mechanism maintains homeostasis of blood gases and acid-base balance. Correct answer: 2

4. SINGLE CORRECT ANSWER MCQ

Which region of the medulla generates the basic rhythm of respiration?

1. Apneustic center

2. Pneumotaxic center

3. Rhythm center

4. Hypothalamus

Explanation: The rhythm center in the medulla, specifically the dorsal and ventral respiratory groups, generates the basic rhythm of breathing. It receives input from central chemoreceptors monitoring CO2 and pH. The apneustic and pneumotaxic centers in the pons modulate rhythm, while the hypothalamus regulates breathing during emotional or temperature changes. Proper function ensures steady ventilation matching metabolic demands. Correct answer: 3

5. SINGLE CORRECT ANSWER MCQ

Which ion indirectly affects central chemoreceptor activity in the medulla?

1. HCO3-

2. Cl-

3. K+

4. Na+

Explanation: HCO3- (bicarbonate) indirectly influences central chemoreceptors by buffering pH changes. Elevated CO2 increases H+ and decreases pH, triggering increased ventilation. Central chemoreceptors detect H+ in cerebrospinal fluid. Other ions like Cl-, K+, and Na+ do not directly regulate respiratory chemoreception. This mechanism maintains acid-base balance and proper oxygen-carbon dioxide homeostasis. Correct answer: 1

6. SINGLE CORRECT ANSWER MCQ

The primary stimulus for increasing ventilation under normal conditions is:

1. Low O2

2. High CO2

3. Low N2

4. High HCO3-

Explanation: High CO2 in blood is the primary stimulus for increasing ventilation under normal physiological conditions. Central chemoreceptors in the medulla detect CO2-induced pH changes, prompting increased breathing to restore homeostasis. Low O2 stimulates peripheral chemoreceptors only in hypoxic conditions. N2 is inert, and HCO3- indirectly affects pH but is not the primary stimulus. Correct answer: 2

7. ASSERTION-REASON MCQ

Assertion (A): Central chemoreceptors respond primarily to CO2 in arterial blood.

Reason (R): Increased CO2 lowers pH in cerebrospinal fluid, stimulating respiration.

1. Both A and R are true and R explains A

2. Both A and R are true but R does not explain A

3. A is true but R is false

4. A is false but R is true

Explanation: Central chemoreceptors in the medulla detect CO2-induced pH changes in cerebrospinal fluid. Elevated CO2 produces H+ ions, lowering pH, which directly stimulates the chemoreceptors to increase respiratory rate and depth. Both Assertion and Reason are true, and the Reason explains the mechanism of central CO2 sensitivity. This system is essential for maintaining acid-base balance and proper oxygen-carbon dioxide homeostasis. Correct answer: 1

8. MATCHING TYPE MCQ

Match the following structures with their respiratory function:

Column A:

1. Medullary chemoreceptors

2. Peripheral chemoreceptors

3. Pneumotaxic center

4. Apneustic center

Column B:

1. Respond to CO2 and pH

2. Respond to O2 and pH

3. Inhibits inspiration, controls rate

4. Promotes inspiration, prolongs inhalation

Explanation: Correct matching: Medullary chemoreceptors → Respond to CO2 and pH, Peripheral chemoreceptors → Respond to O2 and pH, Pneumotaxic center → Inhibits inspiration and controls rate, Apneustic center → Promotes inspiration and prolongs inhalation. These centers coordinate breathing rhythm and maintain homeostasis of blood gases. Correct answer: 1-A, 2-B, 3-C, 4-D

9. FILL IN THE BLANKS / COMPLETION MCQ

The central chemoreceptors detect changes in _______ to regulate respiration.

1. O2

2. CO2

3. N2

4. H2O

Explanation: Central chemoreceptors in the medulla monitor CO2 levels indirectly via H+ ions in cerebrospinal fluid. Elevated CO2 lowers pH, triggering increased ventilation. Oxygen is primarily sensed by peripheral chemoreceptors, while N2 and H2O have negligible effects on central chemoreceptors. This mechanism maintains blood gas homeostasis and acid-base balance. Correct answer: 2

10. CHOOSE THE CORRECT STATEMENTS MCQ

Statement I: Central chemoreceptors respond mainly to CO2 levels.
Statement II: Peripheral chemoreceptors respond mainly to O2 levels.

1. Only Statement I is correct

2. Only Statement II is correct

3. Both Statements I and II are correct

4. Both Statements I and II are incorrect

Explanation: Central chemoreceptors detect CO2-induced pH changes in cerebrospinal fluid, while peripheral chemoreceptors in carotid and aortic bodies respond primarily to low O2. Both mechanisms work together to regulate ventilation and maintain homeostasis. Understanding the distinction between central and peripheral chemoreceptors is crucial for respiratory physiology. Correct answer: 3

Topic: Respiratory Disorders; Subtopic: Alveolar Damage and Gas Exchange

Keyword Definitions:

• Emphysema: A chronic lung disease where alveolar walls are damaged, reducing respiratory surface and impairing gas exchange.

• Alveoli: Tiny air sacs in the lungs where gas exchange occurs between air and blood.

• Respiratory Surface: Area in the lungs available for oxygen and carbon dioxide exchange.

• Asthma: A condition characterized by constriction of bronchi, causing difficulty in breathing but not destruction of alveoli.

• Bronchitis: Inflammation of the bronchial tubes, leading to cough and mucus production, but alveolar walls remain intact.

Lead Question - 2022 (Abroad)
Which of the following disorders represents decrease in respiratory surface due to damaged alveolar walls?
1. Hypocapnia
2. Bronchitis
3. Asthma
4. Emphysema
Explanation: Emphysema is a chronic lung disease characterized by destruction of alveolar walls, leading to a significant reduction in respiratory surface area. This decreases oxygen diffusion capacity, resulting in breathlessness and hypoxia. Unlike asthma or bronchitis, which involve airway constriction or inflammation, emphysema directly reduces the alveolar area, impairing gas exchange efficiency. Risk factors include smoking, air pollution, and genetic predisposition. The condition is progressive and irreversible, highlighting the importance of early prevention and management. It is a prime example of how structural damage to alveoli affects respiratory function.

1. Single Correct Answer Type:
Which symptom is most associated with emphysema?
1. Wheezing
2. Chronic breathlessness
3. Productive cough
4. Fever
Explanation: The hallmark symptom of emphysema is chronic breathlessness due to reduced alveolar surface and impaired oxygen exchange. Unlike bronchitis, which produces cough and mucus, or asthma with wheezing, emphysema primarily affects gas diffusion. Over time, patients may develop barrel-shaped chest and hyperinflated lungs, reflecting air trapping and loss of elasticity in alveoli.

2. Single Correct Answer Type:
Which of the following is a major risk factor for emphysema?
1. Sedentary lifestyle
2. Smoking
3. Viral infections
4. Excessive exercise
Explanation: Smoking is the most significant risk factor for emphysema. Tobacco smoke damages alveolar walls, causing destruction of respiratory surface. Chronic exposure leads to inflammation, elastin degradation, and progressive airflow limitation. Other factors like air pollution and genetic deficiencies (alpha-1 antitrypsin deficiency) can contribute, but smoking remains the primary preventable cause of alveolar damage and reduced gas exchange capacity.

3. Single Correct Answer Type:
Emphysema primarily affects which part of the respiratory system?
1. Bronchi
2. Trachea
3. Alveoli
4. Nasal cavity
Explanation: Alveoli are the primary site affected in emphysema. The walls of alveoli are destroyed, reducing surface area for gas exchange. This leads to hypoxia and hypercapnia. Bronchi and trachea may remain structurally intact, though secondary airflow obstruction can occur. Damage to alveoli also reduces lung elasticity, making exhalation less efficient and contributing to the clinical features of breathlessness and hyperinflation.

4. Single Correct Answer Type:
Which diagnostic test best detects alveolar destruction in emphysema?
1. Chest X-ray
2. Spirometry
3. CT scan of lungs
4. Sputum culture
Explanation: A CT scan of lungs is most sensitive for detecting alveolar destruction in emphysema. It can visualize areas of hyperinflation, bullae formation, and loss of alveolar walls. Spirometry shows airflow limitation but cannot directly visualize alveolar damage. Early detection is critical for management, as emphysema is irreversible and progresses with continued exposure to risk factors.

5. Single Correct Answer Type:
Which physiological change occurs due to emphysema?
1. Increased oxygen diffusion
2. Reduced alveolar surface area
3. Increased mucus production
4. Bronchial constriction
Explanation: Emphysema leads to reduced alveolar surface area, impairing oxygen diffusion. As alveoli are destroyed, less respiratory surface is available for gas exchange, causing hypoxia. Mucus production and bronchial constriction are more characteristic of bronchitis and asthma. The structural loss in emphysema also reduces lung elasticity, causing air trapping and inefficient ventilation, contributing to breathlessness.

6. Single Correct Answer Type:
Which treatment is primarily used to manage emphysema symptoms?
1. Antibiotics
2. Bronchodilators and oxygen therapy
3. Antivirals
4. Steroids only
Explanation: Management of emphysema includes bronchodilators and oxygen therapy to relieve breathlessness and improve oxygenation. While structural damage is irreversible, symptom control improves quality of life. Pulmonary rehabilitation and lifestyle changes like smoking cessation are essential. Antibiotics treat infections but do not reverse alveolar destruction. Oxygen therapy compensates for decreased respiratory surface and impaired gas exchange.

7. Assertion-Reason Type:
Assertion (A): Emphysema causes reduced oxygen intake.
Reason (R): Damage to alveolar walls decreases respiratory surface area.
1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, R is false
4. A is false, R is true
Explanation: Both Assertion and Reason are true. The destruction of alveolar walls in emphysema decreases the surface area for gas exchange, leading to reduced oxygen intake and hypoxia. This direct relationship between structural damage and functional impairment explains the primary pathophysiology of emphysema, distinguishing it from other respiratory conditions like asthma or bronchitis.

8. Matching Type:
Match the respiratory disorder with its primary feature:
A. Emphysema → (i) Airway inflammation
B. Asthma → (ii) Alveolar wall destruction
C. Bronchitis → (iii) Bronchial constriction
D. Hypocapnia → (iv) Low CO₂ in blood
1. A-(ii), B-(iii), C-(i), D-(iv)
2. A-(i), B-(ii), C-(iii), D-(iv)
3. A-(iii), B-(i), C-(iv), D-(ii)
4. A-(iv), B-(ii), C-(i), D-(iii)
Explanation: Correct matching is A-(ii), B-(iii), C-(i), D-(iv). Emphysema is defined by alveolar wall destruction, asthma by bronchial constriction, bronchitis by airway inflammation and mucus production, and hypocapnia refers to decreased blood CO₂. Each disorder has distinct pathological and physiological features, helping differentiate diagnosis and management strategies.

9. Fill in the Blanks Type:
In emphysema, the reduction in _______ leads to decreased oxygen exchange.
1. Bronchial tubes
2. Alveolar surface area
3. Tracheal diameter
4. Lung compliance
Explanation: The correct answer is alveolar surface area. Destruction of alveoli in emphysema directly reduces the area available for oxygen diffusion, causing hypoxia. While lung elasticity also decreases, the primary factor limiting gas exchange is the loss of alveolar walls, which differentiates emphysema from asthma or bronchitis, where alveolar structure is largely intact.

10. Choose the Correct Statements Type:
Which of the following statements about emphysema are correct?
1.

Subtopic: Conducting and Respiratory Portions

Keyword Definitions:

• Conducting part: The portion of the respiratory tract that transports, filters, warms, and humidifies air but does not participate in gas exchange.

• Respiratory part: The portion of the system where gaseous exchange occurs, including bronchioles, alveolar ducts, and alveoli.

• Diffusion: The passive movement of gases like oxygen and carbon dioxide across the respiratory membrane.

• Alveoli: Thin-walled air sacs in lungs where exchange of gases occurs between air and blood.

• Cilia: Hair-like projections lining the respiratory passages that trap and move foreign particles out of the airway.

Lead Question – 2022
Which of the following is not the function of conducting part of respiratory system:
(1) Inhaled air is humidified
(2) Temperature of inhaled air is brought to body temperature
(3) Provides surface for diffusion of O₂ and CO₂
(4) It clears inhaled air from foreign particles

Explanation: The conducting part of the respiratory system filters, warms, and humidifies air but does not take part in gas exchange. Diffusion of O₂ and CO₂ occurs only in the respiratory zone of alveoli. Hence, the correct answer is (3) Provides surface for diffusion of O₂ and CO₂.

1. The actual exchange of gases in humans occurs in:
(1) Alveoli
(2) Trachea
(3) Bronchi
(4) Pharynx
Explanation: Gaseous exchange in humans takes place across the walls of alveoli, which are richly supplied with capillaries. Thus, the correct answer is (1) Alveoli.

2. Which structure connects the larynx to the bronchi?
(1) Trachea
(2) Pharynx
(3) Bronchioles
(4) Alveoli
Explanation: The trachea is a cartilaginous tube that connects the larynx to the bronchi and conducts air into the lungs. Therefore, the correct answer is (1) Trachea.

3. Which of the following forms the respiratory zone?
(1) Nasal cavity and trachea
(2) Bronchi and bronchioles
(3) Alveolar ducts, alveolar sacs, and alveoli
(4) Larynx and trachea
Explanation: The respiratory zone includes alveolar ducts, sacs, and alveoli, where gas exchange occurs between air and blood. The correct answer is (3).

4. Which is a part of conducting portion of human respiratory system?
(1) Alveoli
(2) Bronchioles
(3) Nasal passage
(4) Alveolar sacs
Explanation: The conducting portion includes nasal passage, pharynx, larynx, trachea, bronchi, and terminal bronchioles. Hence, the correct answer is (3) Nasal passage.

5. The respiratory membrane facilitates diffusion of gases due to:
(1) Large surface area and thin walls
(2) Ciliated epithelium
(3) Cartilaginous rings
(4) Mucous glands
Explanation: The alveolar surface provides a large area with very thin walls and moist lining, favoring diffusion of gases. Therefore, the correct answer is (1).

6. The trachea does not collapse due to:
(1) Ciliated epithelium
(2) Elastic fibres
(3) Cartilaginous rings
(4) Mucus secretion
Explanation: The trachea remains open due to the presence of C-shaped cartilaginous rings that prevent collapse during breathing. The correct answer is (3).

7. Assertion (A): The conducting part of the respiratory system purifies and humidifies air.
Reason (R): The alveoli of lungs perform the exchange of gases.
(1) Both A and R are true and R explains A
(2) Both A and R are true but R does not explain A
(3) A is true but R is false
(4) A is false but R is true
Explanation: Both statements are true but the reason describes the respiratory zone, not the conducting part. Hence, (2) Both A and R are true but R is not the correct explanation.

8. Match the following:
A. Trachea — (i) Voice production
B. Larynx — (ii) Air passage to lungs
C. Alveoli — (iii) Gas exchange
Options:
(1) A-(ii), B-(i), C-(iii)
(2) A-(i), B-(iii), C-(ii)
(3) A-(iii), B-(ii), C-(i)
(4) A-(ii), B-(iii), C-(i)
Explanation: The trachea conducts air, the larynx helps in voice production, and alveoli are the site of gas exchange. The correct answer is (1).

9. Fill in the blank:
The exchange of gases takes place in ______ part of the respiratory system.
(1) Conducting
(2) Respiratory
(3) Digestive
(4) Circulatory
Explanation: Gaseous exchange occurs in the respiratory part consisting of alveoli, alveolar ducts, and sacs. Hence, the correct answer is (2) Respiratory.

10. Choose the correct statements:
(1) Conducting part helps in gas exchange.
(2) Respiratory part only filters the air.
(3) Conducting part includes trachea and bronchi.
(4) Alveoli are part of conducting part.
Explanation: The conducting part consists of passages like trachea and bronchi that filter, warm, and humidify air before it reaches alveoli. The correct answer is (3).

Subtopic: Oxygen Transport in Blood

Keyword Definitions:
• Oxygenated Blood: Blood rich in oxygen, mainly found in arteries.
• Hemoglobin: Iron-containing protein in red blood cells that binds and transports oxygen.
• Oxygen Delivery: The amount of oxygen transported to tissues per unit volume of blood.
• Partial Pressure of Oxygen (pO2): Pressure exerted by oxygen in blood plasma.
• Arteries: Blood vessels that carry oxygenated blood from heart to tissues.
• Capillaries: Smallest blood vessels where gas exchange occurs.
• Tissues: Cells and structures that utilize oxygen for respiration.
• Oxygen Saturation: Percentage of hemoglobin binding sites occupied by oxygen.
• Red Blood Cells: Erythrocytes that carry hemoglobin and oxygen.
• Physiological Conditions: Normal body conditions without disease or abnormality.

Lead Question (2022):
Under normal physiological conditions in human beings, every 100 ml of oxygenated blood can deliver __________ ml of O2 to the tissues.
1. 5 ml
2. 4 ml
3. 10 ml
4. 2 ml

Explanation: The correct answer is 1. Under normal physiological conditions, each 100 ml of oxygenated blood delivers approximately 5 ml of oxygen to body tissues. Hemoglobin in red blood cells binds most oxygen, while a small amount is dissolved in plasma, ensuring adequate tissue respiration and energy production.

Guessed MCQs:

1. Which protein primarily carries oxygen in blood?
Options:
(a) Hemoglobin
(b) Myosin
(c) Albumin
(d) Fibrinogen
Explanation: The correct answer is (a) Hemoglobin. Hemoglobin in red blood cells binds oxygen molecules, facilitating transport from lungs to tissues. Albumin and fibrinogen are plasma proteins, while myosin is a muscle protein unrelated to oxygen transport.

2. Single Correct Answer:
Which blood vessel carries oxygenated blood to tissues?
Options:
(a) Arteries
(b) Veins
(c) Capillaries
(d) Lymphatic vessels
Explanation: The correct answer is (a) Arteries. Arteries transport oxygen-rich blood from the heart to tissues, while veins return deoxygenated blood to the heart. Capillaries allow gas exchange, and lymphatic vessels transport lymph, not oxygenated blood.

3. Assertion-Reason MCQ:
Assertion (A): Oxygen delivery to tissues depends on hemoglobin content.
Reason (R): Higher hemoglobin increases oxygen carrying capacity of blood.
Options:
(a) Both A and R are true, R explains A
(b) Both A and R are true, R does not explain A
(c) A is true, R is false
(d) A is false, R is true
Explanation: The correct answer is (a). Oxygen delivery is directly proportional to hemoglobin concentration. Higher hemoglobin increases oxygen binding and transport, ensuring adequate oxygen supply to tissues, which explains the assertion.

4. Matching Type MCQ:
Match the component with its function:
List - I List - II
(a) Hemoglobin (i) Oxygen transport
(b) Plasma (ii) Dissolved oxygen and nutrients
(c) Red blood cells (iii) Carry hemoglobin
Options:
1. a-i, b-ii, c-iii
2. a-iii, b-i, c-ii
3. a-i, b-iii, c-ii
4. a-ii, b-i, c-iii
Explanation: The correct answer is 1. Hemoglobin transports oxygen, plasma carries dissolved oxygen and nutrients, and red blood cells contain hemoglobin to facilitate oxygen delivery to tissues efficiently.

5. Single Correct Answer:
Which factor increases oxygen delivery to tissues?
Options:
(a) Higher hemoglobin concentration
(b) Lower cardiac output
(c) Decreased arterial oxygen saturation
(d) Vasoconstriction
Explanation: The correct answer is (a). Higher hemoglobin increases oxygen carrying capacity. Lower cardiac output, decreased saturation, or vasoconstriction reduces oxygen delivery to tissues, impairing cellular respiration and energy metabolism.

6. Single Correct Answer:
Which molecule carries a small portion of dissolved oxygen in blood?
Options:
(a) Plasma
(b) Hemoglobin
(c) Myoglobin
(d) Carbonic anhydrase
Explanation: The correct answer is (a) Plasma. While hemoglobin carries most oxygen, a small portion remains dissolved in plasma, contributing to oxygen delivery and partial pressure maintenance for diffusion into tissues.

7. Fill in the Blanks:
The total amount of oxygen delivered to tissues depends on hemoglobin content, oxygen saturation, and __________.
Options:
(a) Cardiac output
(b) Blood pressure
(c) Blood viscosity
(d) Respiratory rate
Explanation: The correct answer is (a) Cardiac output. Oxygen delivery equals cardiac output multiplied by arterial oxygen content. Blood pressure, viscosity, and respiratory rate indirectly influence delivery but do not directly determine the total oxygen delivered to tissues.

8. Single Correct Answer:
Which structure is the primary site of oxygen exchange?
Options:
(a) Capillaries
(b) Arteries
(c) Veins
(d) Heart chambers
Explanation: The correct answer is (a) Capillaries. Capillaries have thin walls allowing diffusion of oxygen into tissues. Arteries and veins transport blood, and heart chambers pump blood but are not sites of oxygen exchange.

9. Single Correct Answer:
What is the normal oxygen content delivered per 100 ml of oxygenated blood?
Options:
(a) 5 ml
(b) 10 ml
(c) 2 ml
(d) 8 ml
Explanation: The correct answer is (a) 5 ml. Normally, 100 ml of oxygenated blood delivers approximately 5 ml of oxygen to tissues. Hemoglobin-bound oxygen forms the majority, with a small fraction dissolved in plasma, ensuring efficient cellular respiration.

10. Choose the correct statements:
(a) Hemoglobin binds oxygen reversibly.
(b) Oxygen delivery depends on hemoglobin and cardiac output.
(c) Most oxygen in blood is dissolved in plasma.
(d) Arteries carry oxygenated blood to tissues.
Options:
1. a, b, d only
2. a, c only
3. b, c, d only
4. All statements
Explanation: The correct answer is 1. Hemoglobin binds oxygen reversibly, oxygen delivery depends on hemoglobin concentration and cardiac output, and arteries transport oxygenated blood. Most oxygen is bound to hemoglobin, not dissolved in plasma.

Topic: Respiratory Adaptations

Subtopic: High Altitude Physiology

Keyword Definitions:

• Altitude sickness: A group of symptoms like headache, breathlessness, and palpitations experienced at high altitude due to low oxygen levels.

• Atmospheric pressure: The pressure exerted by the weight of air; decreases at higher altitudes.

• Oxygen availability: The amount of oxygen present in the air; decreases as altitude increases.

• Respiratory adaptation: Physiological changes enabling organisms to survive at varying oxygen concentrations.

Lead Question - 2021

Assertion (A): A person goes to high altitude and experiences 'altitude sickness' with symptoms like breathing difficulty and heart palpitations.
Reason (R): Due to low atmospheric pressure at high altitude, the body does not get sufficient oxygen.
In the light of the above statements, choose the correct answer from the options given below.

(1) Both (A) and (R) are true but (R) is not the correct explanation of (A)
(2) (A) is true but (R) is false
(3) (A) is false but (R) is true
(4) Both (A) and (R) are true and (R) is the correct explanation of (A)

Explanation: Both assertion and reason are correct, and the reason correctly explains the assertion. At high altitude, low barometric pressure reduces oxygen availability, leading to hypoxia. This results in breathlessness and palpitations, commonly termed altitude sickness. Hence, option (4) is correct.

1. Which enzyme facilitates the conversion of carbon dioxide into bicarbonate in RBCs?
(1) Carbonic anhydrase
(2) Catalase
(3) Amylase
(4) Dehydrogenase

Explanation: Carbonic anhydrase catalyzes the rapid conversion of carbon dioxide to bicarbonate inside red blood cells. This enzyme plays a major role in transport of CO₂ and maintenance of acid-base balance. The correct answer is option (1).

2. Which structure prevents food from entering the trachea during swallowing?
(1) Epiglottis
(2) Glottis
(3) Larynx
(4) Vocal cords

Explanation: The epiglottis is a flap-like cartilaginous structure that closes the tracheal opening during swallowing. This prevents food particles from entering the respiratory tract. Hence, option (1) is correct.

3. Which lung volume increases significantly during exercise?
(1) Residual volume
(2) Inspiratory reserve volume
(3) Expiratory reserve volume
(4) Tidal volume

Explanation: During exercise, tidal volume increases to meet higher oxygen demand. More air is inhaled and exhaled per breath to facilitate efficient gas exchange. Therefore, the correct answer is option (4).

4. Which pigment has the highest affinity for oxygen?
(1) Hemocyanin
(2) Hemoglobin
(3) Myoglobin
(4) Chlorocruorin

Explanation: Myoglobin, present in muscles, has higher oxygen affinity than hemoglobin. It serves as an oxygen reservoir, facilitating release during oxygen deficiency in muscles. Thus, option (3) is correct.

5. In alveoli, gaseous exchange occurs primarily by:
(1) Active transport
(2) Simple diffusion
(3) Facilitated diffusion
(4) Osmosis

Explanation: The exchange of gases in alveoli is driven by differences in partial pressure of oxygen and carbon dioxide, allowing simple diffusion. No energy expenditure is required. Correct answer is option (2).

6. Which form carries the maximum amount of carbon dioxide in blood?
(1) Dissolved in plasma
(2) As carbaminohemoglobin
(3) As bicarbonate ions
(4) Attached to plasma proteins

Explanation: Around 70% of carbon dioxide in the blood is carried as bicarbonate ions in plasma, formed after enzymatic conversion in RBCs. Thus, option (3) is correct.

7. Assertion (A): Oxygen dissociation curve is sigmoid shaped.
Reason (R): Hemoglobin shows cooperative binding with oxygen molecules.
(1) Both A and R are true, and R explains A
(2) Both A and R are true, but R does not explain A
(3) A is true, R is false
(4) A is false, R is true

Explanation: The oxygen dissociation curve is sigmoid due to cooperative binding of oxygen with hemoglobin. Binding of one oxygen molecule increases affinity for the next, producing the S-shaped curve. Correct answer is option (1).

8. Match List-I with List-II:
List-I:
(a) Residual volume
(b) Vital capacity
(c) Inspiratory reserve volume
(d) Tidal volume
List-II:
(i) Air remaining after maximal expiration
(ii) Maximum air inspired after normal inspiration
(iii) Maximum air expelled after maximal inspiration
(iv) Normal air exchanged during breathing
Options:
(1) (a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)
(2) (a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
(3) (a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)
(4) (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)

Explanation: Residual volume is air left after maximal expiration, vital capacity is maximum volume expired after maximal inspiration, inspiratory reserve volume is maximum air inspired beyond normal inspiration, tidal volume is normal breathing volume. Correct matching is option (1).

9. Fill in the blank: The respiratory pigment in annelids like earthworm is ______.
(1) Hemoglobin
(2) Hemocyanin
(3) Hemerythrin
(4) Chlorocruorin

Explanation: Earthworms possess hemoglobin dissolved in plasma, unlike vertebrates where it is within RBCs. This pigment binds oxygen and transports it efficiently. Therefore, option (1) is correct.

10. Which of the following statements are correct?
(a) Surfactant prevents alveolar collapse.
(b) Medulla oblongata regulates breathing rhythm.
(c) Bohr’s effect enhances oxygen unloading.
(d) Carbon monoxide increases oxygen binding capacity of hemoglobin.
(1) a, b, c only
(2) b, c, d only
(3) a, c, d only
(4) a, b, d only

Explanation: Surfactant prevents alveolar collapse, medulla regulates breathing rhythm, and Bohr’s effect enhances oxygen release. Carbon monoxide, however, reduces oxygen carrying capacity by binding strongly to hemoglobin. Hence, correct answer is option (1).

Subtopic: Oxygen Transport and Hemoglobin Function

• Oxyhaemoglobin: The combination of oxygen with hemoglobin in red blood cells for transport from lungs to tissues.

• Alveoli: Tiny air sacs in the lungs where gas exchange occurs.

• pO2: Partial pressure of oxygen in blood or alveoli, influencing hemoglobin saturation.

• pCO2: Partial pressure of carbon dioxide affecting oxygen release from hemoglobin (Bohr effect).

• H+ concentration: Measure of acidity; higher H+ lowers hemoglobin affinity for oxygen.

• Temperature: Influences hemoglobin-oxygen affinity; higher temperature decreases affinity.

• Hemoglobin saturation: Percentage of hemoglobin molecules bound to oxygen.

• Bohr effect: The phenomenon where increased CO2 or H+ promotes oxygen release from hemoglobin.

• Oxygen loading: Process of hemoglobin binding oxygen in the lungs under favorable conditions.

• Oxygen unloading: Release of oxygen from hemoglobin in tissues where oxygen is needed.

• Gas exchange: Diffusion of oxygen and carbon dioxide between alveoli and blood.

Lead Question - 2021

Select the favourable conditions required for the formation of oxyhaemoglobin at the alveoli.

(1) Low pO2, high pCO2, more H+, higher temperature
(2) High pO2, high pCO2, less H+, higher temperature
(3) Low pO2, low pCO2, more H+, higher temperature
(4) High pO2, low pCO2, less H+, lower temperature

Explanation: Oxyhaemoglobin forms at alveoli where oxygen concentration is high (high pO2), carbon dioxide concentration is low (low pCO2), hydrogen ion concentration is low (less acidic), and temperature is slightly lower. These conditions favor oxygen binding to hemoglobin. Answer: High pO2, low pCO2, less H+, lower temperature.

1. Single Correct Answer MCQ: The partial pressure of oxygen at alveoli favors oxyhaemoglobin formation when it is:
Options:
A. Low
B. High
C. Zero
D. Moderate

Explanation: High pO2 at alveoli ensures hemoglobin binds oxygen efficiently to form oxyhaemoglobin. Low or zero pO2 would prevent oxygen loading. Answer: High.

2. Single Correct Answer MCQ: Low pCO2 at alveoli promotes:
Options:
A. Oxygen unloading
B. Oxyhaemoglobin formation
C. Acidic conditions
D. CO2 retention

Explanation: Low pCO2 reduces H+ concentration and acidity, enhancing hemoglobin's affinity for oxygen. This favors formation of oxyhaemoglobin in the lungs. Answer: Oxyhaemoglobin formation.

3. Single Correct Answer MCQ: Hemoglobin binds oxygen efficiently under which pH condition?
Options:
A. High H+ concentration
B. Low H+ concentration
C. Neutral pH only
D. Any pH

Explanation: Low H+ concentration (less acidic, higher pH) in alveoli enhances oxygen binding to hemoglobin. High H+ or acidic conditions decrease affinity. Answer: Low H+ concentration.

4. Single Correct Answer MCQ: Temperature effect on oxyhaemoglobin formation at lungs:
Options:
A. Higher temperature favors binding
B. Lower temperature favors binding
C. Temperature has no effect
D. Only body temperature is effective

Explanation: Lower temperature at alveoli favors oxygen binding to hemoglobin, increasing oxyhaemoglobin formation. High temperature decreases affinity. Answer: Lower temperature.

5. Single Correct Answer MCQ: The phenomenon where increased CO2 promotes oxygen release is called:
Options:
A. Bohr effect
B. Haldane effect
C. Fick’s law
D. Henry’s law

Explanation: The Bohr effect describes how high CO2 or H+ reduces hemoglobin affinity for oxygen, promoting release in tissues. At alveoli, low CO2 supports oxygen loading. Answer: Bohr effect.

6. Single Correct Answer MCQ: Oxygen loading in alveoli occurs mainly because of:
Options:
A. Low pO2
B. High pO2
C. High CO2
D. High H+

Explanation: High pO2 at alveoli drives diffusion of oxygen into blood and binding to hemoglobin to form oxyhaemoglobin. Answer: High pO2.

7. Assertion-Reason MCQ:
Assertion (A): Oxyhaemoglobin formation occurs efficiently in lungs.
Reason (R): High pO2, low pCO2, low H+, and lower temperature favor hemoglobin binding oxygen.
Options:
A. Both A and R true, R correct explanation
B. Both A and R true, R not correct explanation
C. A true, R false
D. A false, R true

Explanation: Oxyhaemoglobin forms efficiently in lungs under favorable conditions: high oxygen, low CO2, low H+ concentration, and slightly lower temperature. Reason correctly explains assertion. Answer: Both A and R true, R correct explanation.

8. Matching Type MCQ:
Column I: 1. High pO2 2. Low pCO2 3. Low H+ 4. Low temperature
Column II: A. Promotes oxyhaemoglobin formation B. Causes oxygen release C. Unrelated D. Inhibits binding
Options:
A. 1-A, 2-A, 3-A, 4-A
B. 1-B, 2-B, 3-B, 4-B
C. 1-A, 2-B, 3-A, 4-D
D. 1-B, 2-A, 3-D, 4-C

Explanation: All four factors (high pO2, low pCO2, low H+, low temperature) at alveoli favor oxyhaemoglobin formation. Answer: 1-A, 2-A, 3-A, 4-A.

9. Fill in the Blank MCQ: Oxyhaemoglobin formation is maximal when oxygen partial pressure is ______.
Options:
A. High
B. Low
C. Zero
D. Moderate

Explanation: High oxygen partial pressure at alveoli ensures maximum hemoglobin saturation to form oxyhaemoglobin. Answer: High.

10. Choose the correct statements MCQ:
(a) High pO2 favors oxyhaemoglobin formation.
(b) High pCO2 favors oxygen loading in lungs.
(c) Low H+ concentration promotes binding of oxygen.
(d) Lower temperature increases hemoglobin affinity for oxygen.
Options:
1. (a), (c), (d) only
2. (b) and (c) only
3. (a) and (b) only
4. All of the above

Explanation: Favorable conditions at alveoli include high p

Subtopic: Gas Exchange and Partial Pressures

• Partial Pressure: The pressure exerted by a single gas in a mixture of gases, measured in mm Hg.

• pO2: Partial pressure of oxygen in blood or alveoli, indicating oxygen availability for diffusion.

• pCO2: Partial pressure of carbon dioxide, reflecting CO2 levels for exhalation.

• Alveoli: Tiny air sacs in lungs where gas exchange occurs between air and blood.

• Gas Exchange: Diffusion of O2 into blood and CO2 out of blood at alveoli.

• Diffusion Gradient: Difference in partial pressures driving gas movement across respiratory membrane.

• Arterial Blood: Oxygen-rich blood leaving alveoli, with pO2 around 95 mm Hg and pCO2 around 40 mm Hg.

• Atmospheric Air: Contains pO2 ~159 mm Hg and pCO2 ~0.3 mm Hg at sea level.

• Respiratory Membrane: Thin barrier between alveolar air and blood facilitating diffusion.

• Oxygen Transport: Mainly via hemoglobin in red blood cells.

• Carbon Dioxide Transport: Dissolved, as bicarbonate, and bound to hemoglobin for removal.

Lead Question - 2021

The partial pressures (in mm Hg) of oxygen (O2) and carbon dioxide (CO2) at alveoli (the site of diffusion) are:

1. pO2 = 40 and pCO2 = 45
2. pO2 = 95 and pCO2 = 40
3. pO2 = 159 and pCO2 = 0.3
4. pO2 = 104 and pCO2 = 40

Explanation: At alveoli, the partial pressure of oxygen (pO2) is approximately 95 mm Hg, allowing diffusion into blood, while carbon dioxide (pCO2) is around 40 mm Hg, facilitating removal. This reflects the diffusion gradient between alveolar air and pulmonary capillaries. Answer: pO2 = 95 and pCO2 = 40.

1. The main site of gas exchange in lungs is:
Options:
A. Bronchi
B. Alveoli
C. Trachea
D. Pleura

Explanation: Alveoli are tiny air sacs with thin respiratory membranes that allow oxygen to diffuse into blood and carbon dioxide to exit. Bronchi and trachea conduct air, while pleura is a protective membrane. Answer: Alveoli.

2. Arterial blood leaving alveoli has pO2 approximately:
Options:
A. 40 mm Hg
B. 95 mm Hg
C. 159 mm Hg
D. 104 mm Hg

Explanation: Arterial blood leaving alveoli is oxygenated with pO2 around 95 mm Hg, slightly lower than atmospheric oxygen (159 mm Hg) due to humidification and mixing with residual alveolar air. Answer: 95 mm Hg.

3. Carbon dioxide partial pressure in alveoli is approximately:
Options:
A. 0.3 mm Hg
B. 40 mm Hg
C. 45 mm Hg
D. 95 mm Hg

Explanation: The alveolar pCO2 is about 40 mm Hg, facilitating diffusion from blood to alveoli for exhalation. Atmospheric CO2 is negligible (~0.3 mm Hg). Answer: 40 mm Hg.

4. The diffusion of gases depends on:
Options:
A. Partial pressure gradient
B. Blood viscosity
C. Muscle activity
D. Atmospheric pressure only

Explanation: Gas exchange at alveoli follows partial pressure gradients: O2 moves from alveoli (95 mm Hg) to blood (40 mm Hg), and CO2 moves opposite. Blood viscosity or muscles do not directly drive diffusion. Answer: Partial pressure gradient.

5. The pO2 of atmospheric air at sea level is approximately:
Options:
A. 40 mm Hg
B. 95 mm Hg
C. 104 mm Hg
D. 159 mm Hg

Explanation: Atmospheric air contains pO2 ~159 mm Hg at sea level. Humidification and mixing with residual air in alveoli reduce alveolar pO2 to ~95 mm Hg. Answer: 159 mm Hg.

6. Single correct answer: Alveolar pCO2 is maintained around 40 mm Hg by:
Options:
A. Exhalation of CO2
B. O2 diffusion
C. Residual volume
D. Atmospheric CO2

Explanation: Exhalation of CO2 maintains alveolar pCO2 at ~40 mm Hg, ensuring proper diffusion from blood. Residual volume and atmospheric CO2 minimally affect alveolar CO2. Answer: Exhalation of CO2.

7. Assertion-Reason:
Assertion (A): Alveolar pO2 is lower than atmospheric pO2.
Reason (R): Mixing with residual alveolar air and humidification reduce oxygen concentration.
Options:
A. Both A and R true, R correct explanation
B. Both A and R true, R not correct explanation
C. A true, R false
D. A false, R true

Explanation: Alveolar pO2 (~95 mm Hg) is lower than atmospheric pO2 (~159 mm Hg) because inhaled air mixes with residual air and is humidified, reducing oxygen concentration. Answer: Both A and R true, R correct explanation.

8. Matching Type:
Column I: 1. Alveolar pO2 2. Alveolar pCO2 3. Atmospheric pO2
Column II: A. 95 mm Hg B. 40 mm Hg C. 159 mm Hg
Options:
A. 1-A, 2-B, 3-C
B. 1-B, 2-A, 3-C
C. 1-C, 2-A, 3-B
D. 1-A, 2-C, 3-B

Explanation: Correct matching: Alveolar pO2 – 95 mm Hg, Alveolar pCO2 – 40 mm Hg, Atmospheric pO2 – 159 mm Hg. This reflects normal gas exchange physiology. Answer: 1-A, 2-B, 3-C.

9. Fill in the blank: Oxygen diffuses from alveoli into blood due to _______.
Options:
A. Partial pressure gradient
B. Blood flow rate
C. Hemoglobin concentration
D. Tidal volume

Explanation: Oxygen moves from alveoli (pO2 95 mm Hg) to blood (pO2 40 mm Hg) following the partial pressure gradient, ensuring efficient oxygenation. Other factors assist transport but do not drive diffusion. Answer: Partial pressure gradient.

10. Choose the correct statements:
1. Alveolar pO2 is 95 mm Hg
2. Alveolar pCO2 is 40 mm Hg
3. Atmospheric pO2 is 104 mm Hg
4. Diffusion depends on partial pressure gradients
Options:
A. 1, 2, 4 only
B. 1, 3, 4 only
C. 2, 3 only
D. 1, 2, 3, 4

Explanation: Statements 1, 2, and 4 are correct. Alveolar pO2 is ~95 mm Hg, pCO2 ~40 mm Hg, and diffusion occurs along partial pressure gradients. Atmospheric pO2 is ~159 mm Hg, not 104. Answer: 1, 2, 4 only.

Subtopic: Respiratory Regulation and Gas Transport

Keyword Definitions:
Pneumotaxic Centre: Region in the pons that regulates the rate and pattern of breathing.
Dissociation Curve: Graph showing the relationship between oxygen partial pressure and hemoglobin saturation.
Carbonic Anhydrase: Enzyme in red blood cells catalyzing conversion of CO2 and water to carbonic acid.
Primary site of gas exchange: Alveoli, where oxygen enters blood and carbon dioxide is removed.
R.B.C.: Red Blood Cells, which transport oxygen and carbon dioxide.
Haemoglobin: Oxygen-carrying protein in RBCs.
Pons: Part of brainstem controlling respiration.
Alveoli: Small air sacs in lungs facilitating gas exchange.

Lead Question - 2020 (COVID Reexam):
Match the following columns and select the correct option:
Column - I Column - II
(a) Pneumotaxic Centre (i) Alveoli
(b) Dissociation curve (ii) Pons region of the brain
(c) Carbonic Anhydrase (iii) Haemoglobin
(d) Primary site of exchange (iv) R.B.C.
1. (a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)
2. (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)
3. (a)-(iii), (b)-(ii), (c)-(iv), (d)-(i)
4. (a)-(iv), (b)-(i), (c)-(iii), (d)-(ii)
Explanation: The pneumotaxic centre regulates breathing and is located in the pons (a-ii). Dissociation curve represents oxygen binding with haemoglobin (b-iii). Carbonic anhydrase is present in RBCs (c-iv). The primary site of gas exchange is the alveoli (d-i). Correct answer is 2.

1. Single Correct Answer MCQ:
Which region of the brain regulates breathing rate?
1. Medulla oblongata
2. Pons
3. Cerebellum
4. Hypothalamus
Explanation: The pons contains the pneumotaxic centre which regulates the rate and pattern of breathing. Medulla also contributes but pons specifically modulates inspiratory and expiratory duration. Cerebellum and hypothalamus do not directly control respiration. Correct answer is 2. Pons.

2. Single Correct Answer MCQ:
Carbonic anhydrase is present in:
1. Alveoli
2. RBCs
3. Plasma
4. Bronchioles
Explanation: Carbonic anhydrase is present inside red blood cells and catalyzes the reversible conversion of CO2 and water to carbonic acid, facilitating CO2 transport and pH regulation. It is not present in alveoli, plasma, or bronchioles. Correct answer is 2. RBCs.

3. Single Correct Answer MCQ:
The oxygen dissociation curve represents:
1. CO2 solubility
2. Oxygen saturation of haemoglobin
3. Respiratory rate
4. Tidal volume
Explanation: Dissociation curve illustrates the relationship between oxygen partial pressure and the saturation of haemoglobin, showing how easily hemoglobin acquires and releases oxygen. It does not represent CO2 solubility, respiratory rate, or tidal volume. Correct answer is 2. Oxygen saturation of haemoglobin.

4. Single Correct Answer MCQ:
Primary site for gas exchange in lungs is:
1. Bronchi
2. Alveoli
3. Trachea
4. Bronchioles
Explanation: Alveoli are tiny sacs where oxygen enters the blood and carbon dioxide is removed, forming the primary site for gas exchange. Bronchi, trachea, and bronchioles serve as air passages. Correct answer is 2. Alveoli.

5. Single Correct Answer MCQ:
Haemoglobin is found in:
1. Plasma
2. RBCs
3. White blood cells
4. Platelets
Explanation: Haemoglobin is an oxygen-carrying protein located inside red blood cells. It binds oxygen in lungs and releases it in tissues. Plasma, white blood cells, and platelets do not contain haemoglobin. Correct answer is 2. RBCs.

6. Single Correct Answer MCQ:
Which enzyme helps in CO2 transport in blood?
1. Pepsin
2. Carbonic anhydrase
3. Amylase
4. Lipase
Explanation: Carbonic anhydrase in red blood cells catalyzes CO2 and water conversion to carbonic acid, facilitating CO2 transport in blood. Pepsin digests proteins, amylase digests starch, and lipase digests fats. Correct answer is 2. Carbonic anhydrase.

7. Assertion-Reason MCQ:
Assertion (A): Alveoli are the primary sites of gas exchange.
Reason (R): They provide large surface area and thin walls for diffusion.
1. Both A and R are true, R is correct explanation of A
2. Both A and R are true, R is not correct explanation of A
3. A is true, R is false
4. A is false, R is true
Explanation: Alveoli are the main site for gas exchange, with large surface area and thin walls facilitating oxygen and carbon dioxide diffusion. Both statements are correct, and the reason explains the assertion. Correct answer is 1. Both A and R are true, R is correct explanation.

8. Matching Type MCQ:
Match the item with its description:
A. Pneumotaxic Centre B. Dissociation Curve C. Carbonic Anhydrase D. Primary Gas Exchange
1. RBC enzyme
2. Brain pons region
3. Oxygen-haemoglobin relation
4. Alveoli
Options:
1. A-2, B-3, C-1, D-4
2. A-3, B-2, C-4, D-1
3. A-1, B-4, C-2, D-3
4. A-4, B-1, C-3, D-2
Explanation: Pneumotaxic centre is in the pons (A-2), dissociation curve shows oxygen-haemoglobin relation (B-3), carbonic anhydrase is RBC enzyme (C-1), and alveoli are primary gas exchange site (D-4). Correct answer is 1. A-2, B-3, C-1, D-4.

9. Fill in the Blanks MCQ:
The enzyme _______ catalyzes conversion of CO2 to carbonic acid in RBCs.
1. Pepsin
2. Carbonic Anhydrase
3. Lipase
4. Amylase
Explanation: Carbonic anhydrase in red blood cells catalyzes the reversible reaction of CO2 and water to carbonic acid, facilitating CO2 transport and acid-base balance. Pepsin digests proteins, lipase digests fats, and amylase digests starch. Correct answer is 2. Carbonic Anhydrase.

10. Choose the correct statements MCQ:
Select correct statements:
1. Dissociation curve shows oxygen-hemoglobin relationship
2. Alveoli are primary gas exchange sites
3. Pneumotaxic centre is in medulla
4. Carbonic anhydrase is in RBCs
Options:
1. 1, 2, 4
2. 1 and 3
3. 2 and 3
4. 3 and 4
Explanation: The oxygen dissociation curve shows hemoglobin saturation (1), alveoli are primary gas exchange sites (2), and carbonic anhydrase is in RBCs (4). Pneumotaxic centre is in pons, not medulla. Correct statements are 1, 2, 4. Correct answer is 1. 1, 2, 4.

Subtopic: Lung Volumes and Capacities

Keyword Definitions:
Total Lung Capacity (TLC): Maximum volume of air in lungs after forced inspiration, sum of all lung volumes.
Residual Volume (RV): Air remaining in lungs after maximal exhalation.
Expiratory Reserve Volume (ERV): Extra air exhaled after normal expiration.
Tidal Volume (TV): Volume of air inhaled or exhaled during normal breathing.
Inspiratory Capacity (IC): Maximum air that can be inhaled after normal exhalation.
Vital Capacity (VC): Maximum air exhaled after maximal inhalation.
Functional Residual Capacity (FRC): Air remaining in lungs after normal exhalation.
Expiratory Capacity (EC): Volume exhaled after normal inspiration (less commonly used).

Lead Question - 2020 (COVID Reexam):
The Total Lung Capacity (TLC) is the total volume of air accommodated in the lungs at the end of forced inspiration. This includes:
1. RV; IC (Inspiratory Capacity); EC (Expiratory Capacity); and ERV
2. RV; ERV; IC and EC
3. RV; ERV; VC (Vital Capacity) and FRC (Functional Residual Capacity)
4. RV (Residual Volume); ERV (Expiratory Reserve Volume); TV (Tidal Volume)
Explanation: Total Lung Capacity (TLC) includes all lung volumes: residual volume (RV), expiratory reserve volume (ERV), tidal volume (TV), and inspiratory capacity (IC). Vital capacity (VC) is the sum of TV, IRV, and ERV. Correct combination representing TLC is 4. RV; ERV; TV; IC completes TLC. Correct answer is 4.

1. Single Correct Answer MCQ:
Which volume represents air remaining after maximal exhalation?
1. Tidal Volume
2. Residual Volume
3. Expiratory Reserve Volume
4. Inspiratory Capacity
Explanation: Residual Volume (RV) is the air remaining in lungs after maximal exhalation, preventing lung collapse and allowing continuous gas exchange. Tidal volume is normal breathing, ERV is extra exhalation, and IC is maximal inhalation. Correct answer is 2. Residual Volume.

2. Single Correct Answer MCQ:
Which volume is exhaled beyond normal expiration?
1. Tidal Volume
2. Residual Volume
3. Expiratory Reserve Volume
4. Inspiratory Reserve Volume
Explanation: Expiratory Reserve Volume (ERV) is the additional air exhaled after normal expiration. Tidal volume is normal breath, residual volume remains after maximal exhalation, and inspiratory reserve volume is extra inhalation. Correct answer is 3. Expiratory Reserve Volume.

3. Single Correct Answer MCQ:
Tidal Volume represents:
1. Maximum air inhaled
2. Normal breath air volume
3. Air remaining in lungs
4. Extra air exhaled
Explanation: Tidal Volume (TV) is the amount of air inhaled or exhaled during normal breathing. Maximum air inhaled is IC, air remaining is RV, extra air exhaled is ERV. Correct answer is 2. Normal breath air volume.

4. Single Correct Answer MCQ:
Vital Capacity (VC) includes which volumes?
1. TV + IRV + ERV
2. TV + RV
3. RV + FRC
4. IC + RV
Explanation: Vital Capacity (VC) is the maximum air exhaled after maximal inhalation, consisting of tidal volume (TV), inspiratory reserve volume (IRV), and expiratory reserve volume (ERV). RV remains in lungs and is not part of VC. Correct answer is 1. TV + IRV + ERV.

5. Single Correct Answer MCQ:
Functional Residual Capacity (FRC) is:
1. TV + IRV
2. RV + ERV
3. IC + TV
4. TV + ERV
Explanation: Functional Residual Capacity (FRC) is the air left in lungs after normal exhalation, which includes residual volume (RV) plus expiratory reserve volume (ERV). TV is normal breathing, IC is maximal inhalation. Correct answer is 2. RV + ERV.

6. Single Correct Answer MCQ:
Which lung capacity measures maximum air inhaled after normal exhalation?
1. Tidal Volume
2. Inspiratory Capacity
3. Expiratory Reserve Volume
4. Vital Capacity
Explanation: Inspiratory Capacity (IC) is the maximum volume of air inhaled after a normal exhalation. Tidal volume is normal breath, ERV is extra exhaled air, and VC is maximal exhalation after maximal inhalation. Correct answer is 2. Inspiratory Capacity.

7. Assertion-Reason MCQ:
Assertion (A): TLC is the sum of all lung volumes.
Reason (R): It includes TV, IRV, ERV, and RV.
1. Both A and R are true, R is correct explanation of A
2. Both A and R are true, R is not correct explanation of A
3. A is true, R is false
4. A is false, R is true
Explanation: Total Lung Capacity (TLC) represents the sum of all lung volumes, including tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume. The reason correctly explains the assertion. Correct answer is 1. Both A and R are true, R is correct explanation.

8. Matching Type MCQ:
Match the lung volume with its description:
A. RV B. TV C. ERV D. IC
1. Normal breath air
2. Extra air inhaled
3. Extra air exhaled
4. Air remaining after maximal exhalation
Options:
1. A-4, B-1, C-3, D-2
2. A-1, B-2, C-3, D-4
3. A-3, B-1, C-2, D-4
4. A-2, B-3, C-1, D-4
Explanation: Residual Volume (RV) remains after maximal exhalation (A-4), Tidal Volume (TV) is normal breath (B-1), Expiratory Reserve Volume (ERV) is extra air exhaled (C-3), and Inspiratory Capacity (IC) is extra air inhaled (D-2). Correct answer is 1. A-4, B-1, C-3, D-2.

9. Fill in the Blanks MCQ:
Total Lung Capacity (TLC) = RV + TV + ERV + _______.
1. IC
2. FRC
3. VC
4. EC
Explanation: Total Lung Capacity is the sum of all lung volumes, including residual volume, tidal volume, expiratory reserve volume, and inspiratory capacity. FRC and VC are parts of TLC but IC completes the calculation. Correct answer is 1. IC.

10. Choose the correct statements MCQ:
Select correct statements about TLC:
1. Sum of all lung volumes
2. Includes RV, TV, ERV, IC
3. Only measures air exhaled
4. Does not include residual volume
Options:
1. 1 and 2
2. 2 and 3
3. 3 and 4
4. 1 and 4
Explanation: Total Lung Capacity is the sum of all lung volumes and includes residual volume, tidal volume, expiratory reserve volume, and inspiratory capacity. It measures total air in lungs, not just exhaled air. Correct statements are 1 and 2. Correct answer is 1. 1 and 2.

Subtopic: Mechanics of Breathing

Keyword Definitions:

• Inspiration – Process of drawing air into the lungs during breathing.

• Diaphragm – Dome-shaped muscle separating thoracic and abdominal cavities, contracts to facilitate inhalation.

• External intercostal muscles – Muscles between ribs, contract to elevate rib cage and expand thoracic volume.

• Pulmonary volume – Total volume of air in the lungs, varies during breathing cycles.

• Intra-pulmonary pressure – Pressure inside the lungs relative to atmospheric pressure, decreases during inspiration.

• Expiration – Process of expelling air from lungs.

• Thoracic cavity – Chamber enclosed by ribs and diaphragm housing lungs and heart.

• Alveoli – Microscopic air sacs in lungs where gas exchange occurs.

• Respiratory muscles – Muscles facilitating inhalation and exhalation, including diaphragm and intercostals.

• Atmospheric pressure – Pressure exerted by surrounding air outside the body.

• Boyle’s Law – Principle explaining inverse relationship between volume and pressure in lungs during breathing.

Lead Question - 2020

Select the correct events that occur during inspiration:
(a) Contraction of diaphragm
(b) Contraction of external inter-costal muscles
(c) Pulmonary volume decreases
(d) Intra pulmonary pressure increases
(1) (a), (b) and (d)
(2) only (d)
(3) (a) and (b)
(4) (c) and (d)

Explanation: During inspiration, the diaphragm and external intercostal muscles contract, enlarging thoracic cavity volume. This increases pulmonary volume and decreases intra-pulmonary pressure, allowing air to flow into lungs. Therefore, the correct events are contraction of diaphragm and external intercostals. Correct answer is (3) (a) and (b).

1. Single Correct Answer: What happens to intra-pulmonary pressure during inspiration?
(1) Increases
(2) Decreases
(3) Remains same
(4) Becomes equal to atmospheric pressure

Explanation: Intra-pulmonary pressure decreases below atmospheric pressure during inspiration, allowing air to enter the lungs due to the pressure gradient. Correct answer is (2) Decreases.

2. Single Correct Answer: Which muscle is primarily responsible for inhalation?
(1) Diaphragm
(2) Rectus abdominis
(3) Internal intercostals
(4) Sternocleidomastoid

Explanation: The diaphragm contracts during inspiration, moving downward to expand thoracic cavity and facilitate airflow into the lungs. Correct answer is (1) Diaphragm.

3. Single Correct Answer: Contraction of external intercostal muscles leads to:
(1) Rib cage depression
(2) Rib cage elevation
(3) Thoracic cavity reduction
(4) Lung collapse

Explanation: External intercostal muscles contract to elevate the ribs, expanding thoracic volume and aiding inspiration. Correct answer is (2) Rib cage elevation.

4. Single Correct Answer: Pulmonary volume during inspiration:
(1) Increases
(2) Decreases
(3) Remains constant
(4) Becomes zero

Explanation: Pulmonary volume increases as thoracic cavity enlarges during inspiration, decreasing intra-pulmonary pressure and allowing air inflow. Correct answer is (1) Increases.

5. Assertion-Reason:
Assertion (A): Inspiration occurs when intra-pulmonary pressure falls below atmospheric pressure.
Reason (R): Contraction of diaphragm and external intercostals increases thoracic cavity volume.
(1) Both A and R true, R explains A
(2) Both A and R true, R does not explain A
(3) A true, R false
(4) A false, R true

Explanation: Inspiration results from decreased intra-pulmonary pressure below atmospheric pressure, caused by diaphragm and external intercostal contraction increasing thoracic volume. Both assertion and reason are true, and reason correctly explains assertion. Correct answer is (1).

6. Single Correct Answer: Which process occurs actively during quiet breathing?
(1) Expiration
(2) Inspiration
(3) Gas exchange at alveoli
(4) Diffusion only

Explanation: Inspiration during quiet breathing is an active process involving muscle contraction, whereas expiration is mostly passive. Correct answer is (2) Inspiration.

7. Matching Type: Match structure with function during inspiration:
(a) Diaphragm – i. Expands thoracic cavity
(b) External intercostals – ii. Elevates ribs
(c) Internal intercostals – iii. Forced expiration
(d) Lungs – iv. Receive air
Options:
(1) a-i, b-ii, c-iii, d-iv
(2) a-ii, b-i, c-iv, d-iii
(3) a-i, b-iii, c-ii, d-iv
(4) a-iv, b-ii, c-i, d-iii

Explanation: Diaphragm expands thoracic cavity (a-i), external intercostals elevate ribs (b-ii), internal intercostals act in forced expiration (c-iii), and lungs receive air (d-iv). Correct answer is (1).

8. Fill in the blank: During inspiration, _______ moves downward to increase thoracic cavity volume.
(1) Diaphragm
(2) Heart
(3) Stomach
(4) Liver

Explanation: The diaphragm contracts and moves downward during inspiration, enlarging thoracic cavity and reducing intra-pulmonary pressure. Correct answer is (1) Diaphragm.

9. Single Correct Answer: Which statement is true about quiet inspiration?
(1) Passive process
(2) Diaphragm relaxes
(3) Thoracic volume increases
(4) Intra-pulmonary pressure rises

Explanation: Quiet inspiration is active, involving diaphragm contraction, elevating thoracic volume and lowering intra-pulmonary pressure. Correct answer is (3) Thoracic volume increases.

10. Choose the correct statements:
(a) Diaphragm contracts during inspiration
(b) External intercostals contract during inspiration
(c) Pulmonary volume decreases during inspiration
(d) Intra-pulmonary pressure falls during inspiration
Options:
(1) a, b, d
(2) a, c, d
(3) b, c, d
(4) a, b, c

Explanation: During inspiration, diaphragm and external intercostals contract, increasing pulmonary volume and lowering intra-pulmonary pressure. Pulmonary volume does not decrease. Correct answer is (1) a, b, d.

Topic: Transport of Gases
Subtopic: Oxygen Transport in Blood

• Oxyhaemoglobin: Complex of oxygen bound to haemoglobin in red blood cells for transport from lungs to tissues.

• Partial Pressure of Oxygen (pO2): Measure of oxygen concentration in blood or alveoli influencing haemoglobin binding.

• Partial Pressure of Carbon Dioxide (pCO2): Measure of CO2 concentration in blood or alveoli affecting oxygen transport and affinity.

• Bohr Effect: Influence of pH and CO2 concentration on haemoglobin's oxygen binding capacity.

• Haemoglobin: Protein in red blood cells that binds oxygen and facilitates transport.

• Alveoli: Air sacs in lungs where gas exchange occurs.

• Acid-Base Balance: Regulation of blood pH affecting oxygen delivery.

• Oxygen Saturation: Percentage of haemoglobin bound with oxygen in blood.

• Carbonic Anhydrase: Enzyme that catalyzes conversion of CO2 to bicarbonate in red blood cells.

• Oxygen-Haemoglobin Dissociation Curve: Graph showing relation between pO2 and haemoglobin saturation.

• Affinity: Tendency of haemoglobin to bind oxygen, influenced by pH, CO2, and temperature.

Lead Question (2020): Identify the wrong statement with reference to transport of oxygen:
Options:
1. Higher H+ conc. in alveoli favours the formation of oxyhaemoglobin
2. Low pCO2 in alveoli favours the formation of oxyhaemoglobin
3. Binding of oxygen with haemoglobin is mainly related to partial pressure of O2
4. Partial pressure of CO2 can interfere with O2 binding with haemoglobin

Explanation: Correct answer is 1. Higher H+ concentration decreases haemoglobin’s affinity for oxygen (Bohr effect), reducing oxyhaemoglobin formation. Low pCO2 favours oxygen binding, binding primarily depends on pO2, and elevated CO2 can interfere with oxygen transport by shifting the dissociation curve.

1. Single Correct Answer MCQ:
What does the Bohr effect describe?
Options:
a. Effect of CO2 and H+ on oxygen binding
b. Effect of temperature on respiration
c. Effect of hemoglobin mutations
d. Effect of oxygen on CO2 binding

Explanation: Correct answer is a. The Bohr effect describes decreased oxygen affinity of haemoglobin due to increased H+ and CO2, facilitating oxygen release in tissues. This physiological adaptation optimizes oxygen transport according to tissue metabolic demands.

2. Single Correct Answer MCQ:
Which factor primarily determines oxygen binding to haemoglobin?
Options:
a. pO2
b. pCO2
c. Blood glucose
d. Body temperature

Explanation: Correct answer is a. Oxygen binding to haemoglobin depends mainly on pO2. Higher pO2 in alveoli promotes oxygen loading, while lower pO2 in tissues facilitates release. Other factors like pH and CO2 influence but do not primarily determine oxygen binding.

3. Single Correct Answer MCQ:
Which gas interferes with oxygen binding to haemoglobin?
Options:
a. CO2
b. N2
c. O2
d. H2

Explanation: Correct answer is a. Carbon dioxide interferes with oxygen binding by lowering blood pH and promoting release of oxygen (Bohr effect). N2, O2, and H2 do not directly affect haemoglobin’s oxygen affinity in physiological conditions.

4. Single Correct Answer MCQ:
Low pCO2 in alveoli causes:
Options:
a. Formation of oxyhaemoglobin
b. Release of oxygen
c. Increased acidity
d. Decreased pO2

Explanation: Correct answer is a. Low alveolar pCO2 reduces H+ concentration, increasing haemoglobin’s affinity for oxygen and promoting oxyhaemoglobin formation. This ensures efficient oxygen loading in lungs while CO2 transport occurs simultaneously.

5. Single Correct Answer MCQ:
Where does maximum oxyhaemoglobin formation occur?
Options:
a. Lungs alveoli
b. Tissues
c. Capillaries
d. Veins

Explanation: Correct answer is a. Maximum oxyhaemoglobin formation occurs in alveoli of lungs where pO2 is high and pCO2 is low, facilitating efficient oxygen uptake. Tissue capillaries with lower pO2 promote oxygen release.

6. Single Correct Answer MCQ:
Which factor shifts the oxygen-haemoglobin dissociation curve to the right?
Options:
a. Increased CO2 and H+
b. Low temperature
c. Decreased CO2
d. High pO2

Explanation: Correct answer is a. Increased CO2 and H+ reduce haemoglobin’s oxygen affinity, shifting the curve right, promoting oxygen release to tissues. Low temperature or low CO2 shifts the curve left, enhancing oxygen binding.

7. Assertion-Reason MCQ:
Assertion (A): Oxygen transport depends on both pO2 and pCO2.
Reason (R): pCO2 and H+ affect haemoglobin’s affinity for oxygen.
Options:
a. Both A and R are true, R explains A
b. Both A and R are true, R does not explain A
c. A is true, R is false
d. A is false, R is true

Explanation: Correct answer is a. Oxygen transport is influenced by pO2 for loading and pCO2/H+ for unloading (Bohr effect). The reason explains the assertion since CO2 and H+ modify haemoglobin affinity, ensuring tissue oxygen delivery matches metabolic demand.

8. Matching Type MCQ:
Match the site with oxygen transport characteristic:
(a) Lungs | (i) Oxygen unloading
(b) Tissues | (ii) High pO2, low pCO2
(c) Arterioles | (iii) Oxygen delivery
(d) Capillaries | (iv) Moderate pO2, high pCO2
Options:
1. a-ii, b-i, c-iii, d-iv
2. a-i, b-ii, c-iii, d-iv
3. a-iii, b-iv, c-ii, d-i
4. a-iv, b-iii, c-i, d-ii

Explanation: Correct answer is 1. Lungs have high pO2 and low pCO2 (a-ii) favoring oxygen loading. Tissues promote oxygen unloading (b-i). Arterioles deliver oxygen (c-iii) and capillaries have moderate pO2 and high CO2 (d-iv), optimizing gas exchange.

9. Fill in the Blanks MCQ:
The decrease in haemoglobin’s oxygen affinity due to high H+ is called ________.
Options:
a. Bohr effect
b. Haldane effect
c. Fick’s law
d. Dalton’s law

Explanation: Correct answer is a. The Bohr effect describes decreased haemoglobin affinity for oxygen in response to increased H+ concentration, facilitating oxygen release in metabolically active tissues while maintaining efficient transport in lungs.

Subtopic: Lung Volumes and Capacities

• Tidal Volume (TV): The volume of air inhaled or exhaled in a normal breath, typically 400–500 mL.

• Expiratory Reserve Volume (ERV): The additional volume of air that can be exhaled after normal expiration.

• Residual Volume (RV): The volume of air remaining in lungs after maximal exhalation, cannot be voluntarily expelled.

• Expiratory Capacity (EC): The total air that can be exhaled after a normal inspiration; EC = TV + ERV.

• Lung Volumes: Different measurable amounts of air in lungs at various stages of respiration.

• Lung Capacities: Combination of two or more lung volumes representing functional aspects of respiratory system.

• Athlete: A person with high physical fitness and often increased lung capacities.

• Respiratory Mechanics: Study of ventilation, lung volumes, and airflow dynamics.

• Maximal Expiration: Complete exhalation following a deep inhalation.

• Ventilation: Movement of air into and out of the lungs.

• Pulmonary Function: Functional assessment of lung volumes, capacities, and gas exchange efficiency.

Lead Question (2019): Tidal Volume and Expiratory Reserve Volume of an athlete is 500 mL and 1000 mL respectively. What will be his Expiratory Capacity if the Residual Volume is 1200 mL?

Options:
1. 1500 mL
2. 1700 mL
3. 2200 mL
4. 2700 mL

Explanation: Correct answer is 1. Expiratory Capacity (EC) is the sum of Tidal Volume and Expiratory Reserve Volume. Here, EC = TV + ERV = 500 mL + 1000 mL = 1500 mL. Residual volume is not included in EC calculation. This reflects the maximum volume of air exhaled after a normal inspiration.

1. Single Correct Answer MCQ:
The total lung capacity (TLC) is the sum of:
Options:
a. TV + ERV
b. TV + ERV + RV + Inspiratory Reserve Volume
c. TV + RV
d. ERV + RV

Explanation: Correct answer is b. Total lung capacity includes Tidal Volume, Expiratory Reserve Volume, Residual Volume, and Inspiratory Reserve Volume. It represents the maximum volume of air the lungs can hold, providing a measure of pulmonary function and respiratory efficiency.

2. Single Correct Answer MCQ:
Functional Residual Capacity (FRC) equals:
Options:
a. TV + ERV
b. ERV + RV
c. TV + IRV
d. TLC - TV

Explanation: Correct answer is b. Functional Residual Capacity is the volume of air remaining in lungs after a normal expiration, calculated as ERV + RV. It represents the baseline air available for gas exchange between breaths.

3. Single Correct Answer MCQ:
An athlete usually has higher than normal:
Options:
a. Residual Volume
b. Lung Compliance
c. Tidal Volume
d. Dead Space

Explanation: Correct answer is c. Athletes often have increased Tidal Volume due to enhanced respiratory efficiency. Residual volume and dead space remain relatively constant, while lung compliance may improve slightly. Higher tidal volume improves oxygen intake during intense physical activity.

4. Single Correct Answer MCQ:
Expiratory Reserve Volume is best described as:
Options:
a. Air exhaled during normal breath
b. Air that can be forcefully exhaled after normal expiration
c. Air remaining after maximal exhalation
d. Total lung air capacity

Explanation: Correct answer is b. ERV is the additional air that can be expelled after normal exhalation, reflecting the reserve capacity of lungs. It is distinct from residual volume, which cannot be exhaled, and tidal volume, which represents normal breathing.

5. Single Correct Answer MCQ:
Which lung volume cannot be voluntarily exhaled?
Options:
a. Tidal Volume
b. Expiratory Reserve Volume
c. Residual Volume
d. Inspiratory Reserve Volume

Explanation: Correct answer is c. Residual Volume is the air remaining in lungs after maximal exhalation. It prevents lung collapse and maintains continuous gas exchange. Other volumes, like TV, ERV, and IRV, can be voluntarily inhaled or exhaled.

6. Single Correct Answer MCQ:
Vital Capacity (VC) is calculated as:
Options:
a. TV + ERV
b. TV + IRV + ERV
c. TLC - RV
d. b and c both

Explanation: Correct answer is d. Vital Capacity, the maximum air exhaled after full inspiration, equals TV + IRV + ERV or TLC - RV. It measures lung performance and functional reserve, critical in assessing respiratory health.

7. Assertion-Reason MCQ:
Assertion (A): Expiratory Capacity increases in athletes.
Reason (R): Tidal Volume and Expiratory Reserve Volume are higher in trained individuals.
Options:
a. Both A and R are true, R explains A
b. Both A and R are true, R does not explain A
c. A is true, R is false
d. A is false, R is true

Explanation: Correct answer is a. Athletes have higher Tidal Volume and Expiratory Reserve Volume, which increases Expiratory Capacity. Both assertion and reason are correct, and reason explains the physiological basis for the higher EC observed in trained individuals.

8. Matching Type MCQ:
Match the lung volumes with their description:
Column-I Column-II
(a) Tidal Volume (i) Air remaining after maximal exhalation
(b) Expiratory Reserve Volume (ii) Normal breath exhaled air
(c) Residual Volume (iii) Maximal air exhaled after normal expiration
(d) Inspiratory Reserve Volume (iv) Maximal air inhaled after normal inspiration
Options:
1. a-ii, b-iii, c-i, d-iv
2. a-i, b-ii, c-iii, d-iv
3. a-iii, b-ii, c-i, d-iv
4. a-iv, b-iii, c-ii, d-i

Explanation: Correct answer is 1. Tidal Volume is normal exhalation, ERV is air forcibly exhaled after normal breath, Residual Volume cannot be exhaled, and IRV is air forcibly inhaled. Correct matching demonstrates understanding of lung volume distinctions.

9. Fill in the Blanks / Completion MCQ:
Expiratory Capacity is equal to ________ + ________.
Options:
a. TV + IRV

Subtopic: Respiratory Disorders

Keyword Definitions:

• Wheezing: High-pitched whistling sound during breathing due to airway obstruction.

• Bronchi: Large air passages that lead from trachea to lungs.

• Bronchioles: Smaller branches of bronchi within the lungs.

• Alveoli: Tiny air sacs in lungs for gas exchange.

• Surfactants: Substances secreted by pneumocytes to reduce surface tension in alveoli.

• Inflammation: Immune response causing swelling and irritation of tissues.

• Allergens: Substances that trigger allergic reactions.

Lead Question (2019):

Due to increasing air-borne allergens and pollutants, many people in urban areas are suffering from respiratory disorder causing wheezing due to:
(1) benign growth on mucous lining of nasal cavity.
(2) inflammation of bronchi and bronchioles
(3) proliferation of fibrous tissues and damage of the alveolar walls.
(4) reduction in the secretion of surfactants by pneumocytes

Explanation: Correct answer is (2). Wheezing occurs due to narrowing and inflammation of bronchi and bronchioles, typical in conditions like asthma or bronchitis. Airway obstruction caused by allergens or pollutants triggers smooth muscle contraction, mucous production, and inflammation, resulting in difficulty breathing and characteristic whistling sounds.

1) Single Correct Answer MCQ:
Which cells produce surfactants in lungs?
(1) Ciliated epithelial cells
(2) Pneumocytes
(3) Goblet cells
(4) Alveolar macrophages

Explanation: Correct answer is (2). Pneumocytes, specifically type II alveolar cells, secrete surfactants that reduce surface tension, preventing alveolar collapse and facilitating gas exchange in the lungs.

2) Single Correct Answer MCQ:
Chronic inflammation of bronchi is known as:
(1) Asthma
(2) Bronchitis
(3) Emphysema
(4) Pneumonia

Explanation: Correct answer is (2). Bronchitis is inflammation of the bronchi, leading to cough, mucus production, and wheezing. Acute or chronic exposure to allergens or pollutants often triggers the condition.

3) Single Correct Answer MCQ:
Wheezing is primarily caused by:
(1) Alveolar collapse
(2) Airway narrowing
(3) Pulmonary edema
(4) Pneumothorax

Explanation: Correct answer is (2). Wheezing results from narrowing of the bronchi and bronchioles due to inflammation, smooth muscle contraction, and mucus accumulation, producing high-pitched sounds during exhalation.

4) Single Correct Answer MCQ:
Which pollutant commonly triggers airway inflammation?
(1) Nitrogen oxides
(2) Carbon monoxide
(3) Ozone
(4) All of the above

Explanation: Correct answer is (4). Nitrogen oxides, carbon monoxide, and ozone are air pollutants that irritate the respiratory tract, causing inflammation, bronchoconstriction, and wheezing in sensitive individuals.

5) Single Correct Answer MCQ:
Allergic asthma is triggered by:
(1) Viral infection
(2) Airborne allergens
(3) Bacterial infection
(4) High blood pressure

Explanation: Correct answer is (2). Airborne allergens such as pollen, dust, and mold can trigger immune-mediated inflammation in bronchi, resulting in asthma symptoms including wheezing and shortness of breath.

6) Single Correct Answer MCQ:
Which structure connects trachea to lungs?
(1) Bronchi
(2) Bronchioles
(3) Alveoli
(4) Larynx

Explanation: Correct answer is (1). The bronchi are major air passages branching from the trachea into each lung, further dividing into bronchioles, and play a key role in conducting air and being susceptible to inflammation.

7) Assertion-Reason MCQ:
Assertion (A): Wheezing occurs due to airway inflammation.
Reason (R): Pollutants and allergens trigger smooth muscle contraction and mucus secretion in bronchi.
Options:
(1) A true, R true, R correct explanation
(2) A true, R true, R not correct explanation
(3) A true, R false
(4) A false, R true

Explanation: Correct answer is (1). Wheezing results from inflamed and narrowed airways. Allergens and pollutants stimulate bronchial smooth muscles to contract and increase mucus production, directly explaining the occurrence of wheezing.

8) Matching Type MCQ:
Match the disorder with primary affected structure:
(a) Asthma - (i) Alveoli
(b) Bronchitis - (ii) Bronchi
(c) Emphysema - (iii) Bronchioles
Options:
(1) a-iii, b-ii, c-i
(2) a-ii, b-i, c-iii
(3) a-i, b-iii, c-ii
(4) a-ii, b-iii, c-i

Explanation: Correct answer is (1). Asthma affects bronchioles, bronchitis affects bronchi, and emphysema involves alveolar wall damage, reducing gas exchange efficiency.

9) Fill in the Blanks MCQ:
_________ cells in alveoli secrete surfactants to prevent collapse.
(1) Type I pneumocytes
(2) Type II pneumocytes
(3) Goblet cells
(4) Ciliated epithelial cells

Explanation: Correct answer is (2). Type II pneumocytes produce surfactants that lower surface tension in alveoli, ensuring structural stability during breathing cycles.

10) Choose the correct statements MCQ:
(1) Bronchioles are smaller branches of bronchi
(2) Wheezing is caused by airway narrowing
(3) Allergens can trigger inflammation of bronchi
(4) Pneumocytes produce surfactants to reduce alveolar collapse

Explanation: Correct answer is (1,2,3,4). All statements are correct. Bronchioles conduct air from bronchi to alveoli, wheezing arises from airway constriction, allergens cause inflammation, and pneumocytes secrete surfactants to maintain alveolar stability.</

Subtopic: Lung Volumes and Capacities

Keyword Definitions:

• Tidal volume (TV): Volume of air inhaled or exhaled in a normal breath, ~500 mL.

• Inspiratory Reserve Volume (IRV): Maximum air inhaled beyond normal inspiration, ~2500–3000 mL.

• Expiratory Reserve Volume (ERV): Maximum air exhaled beyond normal expiration, ~1100–1200 mL.

• Residual Volume (RV): Air remaining in lungs after forceful expiration, ~1000–1100 mL.

• Lung capacity: Sum of various lung volumes.

• Pulmonary ventilation: Total air movement in and out of lungs.

Lead Question - 2018

Match the items given in Column I with those in Column II and select the correct option given below :

Column –I | Column –II

a. Tidal volume | i. 2500 – 3000 mL

b. Inspiratory Reserve volume | ii. 1100 - 1200 mL

c. Expiratory Reserve volume | iii. 500 – 550 mL

d. Residual volume | iv. 1000 – 1100 mL

(A) a – iv, b – iii, c – ii, d – i

(B) a – iii, b – ii, c – i, d - iv

(C) a – i, b – iv, c – ii, d – iii

(D) a – iii, b – i, c – iv, d – ii

Explanation:

Answer is (B). Tidal volume (TV) is 500–550 mL, Inspiratory Reserve Volume (IRV) is 2500–3000 mL, Expiratory Reserve Volume (ERV) is 1100–1200 mL, and Residual Volume (RV) is 1000–1100 mL. This matching correctly reflects normal human adult lung volumes.

Guessed NEET UG MCQs:

1) Single Correct: The total lung capacity (TLC) is approximately:

(A) 3000 mL

(B) 4000 mL

(C) 5500 mL

(D) 6000 mL

Explanation:

Answer is (C). Total lung capacity is the sum of all lung volumes: TV + IRV + ERV + RV, which totals around 5500 mL in an average adult.

2) Single Correct: During normal quiet breathing, which volume is primarily used?

(A) IRV

(B) ERV

(C) TV

(D) RV

Explanation:

Answer is (C). Tidal volume, approximately 500 mL, is the air exchanged during normal quiet breathing without extra effort.

3) Single Correct: Maximum additional air inhaled after normal inspiration is:

(A) Tidal volume

(B) Inspiratory Reserve Volume

(C) Expiratory Reserve Volume

(D) Residual Volume

Explanation:

Answer is (B). Inspiratory Reserve Volume is the extra volume inhaled beyond tidal volume, typically 2500–3000 mL, crucial during deep breathing.

4) Assertion-Reason:

Assertion: Residual volume prevents lung collapse.

Reason: RV maintains alveolar inflation even after maximal exhalation.

(A) Both true, Reason correct

(B) Both true, Reason incorrect

(C) Assertion true, Reason false

(D) Both false

Explanation:

Answer is (A). Residual volume keeps alveoli partially inflated, preventing lung collapse and ensuring continuous gas exchange, making the reason correct.

5) Single Correct: Maximum air exhaled after normal expiration is:

(A) IRV

(B) ERV

(C) TV

(D) RV

Explanation:

Answer is (B). Expiratory Reserve Volume is the air expelled beyond normal expiration, around 1100–1200 mL, helping to measure lung capacity clinically.

6) Single Correct: Volume remaining in lungs after forceful exhalation is:

(A) TV

(B) IRV

(C) ERV

(D) RV

Explanation:

Answer is (D). Residual Volume, about 1000–1100 mL, ensures lungs are never completely empty, preventing alveolar collapse and maintaining gas exchange.

7) Matching Type:

Column I | Column II

a. Tidal volume | i. 500 mL

b. Inspiratory Reserve Volume | ii. 2500 mL

c. Expiratory Reserve Volume | iii. 1100 mL

d. Residual Volume | iv. 1000 mL

(A) a-i, b-ii, c-iii, d-iv

(B) a-ii, b-i, c-iv, d-iii

(C) a-iii, b-iv, c-ii, d-i

(D) a-iv, b-iii, c-ii, d-i

Explanation:

Answer is (A). Tidal volume 500 mL, IRV 2500 mL, ERV 1100 mL, and RV 1000 mL correctly match standard adult lung volumes.

8) Fill in the Blank:

The volume of air that remains in lungs after maximal exhalation is ______.

(A) TV

(B) IRV

(C) ERV

(D) RV

Explanation:

Answer is (D). Residual Volume is the air remaining in lungs after maximum exhalation, preventing alveolar collapse and maintaining continuous gas exchange.

9) Choose the correct statements:

(i) Tidal volume is used in quiet breathing.

(ii) IRV is greater than ERV.

(iii) RV can be measured directly using a spirometer.

(A) i and ii only

(B) i and iii only

(C) ii and iii only

(D) i, ii, iii

Explanation:

Answer is (A). Tidal volume is used during normal breathing, IRV is larger than ERV. RV cannot be measured directly as it remains in lungs after maximal exhalation.

10) Clinical-type: A patient with emphysema shows increased RV. Which physiological effect is expected?

(A) Reduced lung compliance

(B) Hyperinflated lungs

(C) Increased tidal volume

(D) Decreased IRV

Explanation:

Answer is (B). Emphysema causes alveolar wall destruction, trapping air and increasing residual volume, leading to hyperinflated lungs and impaired gas exchange.

Subtopic: Lung Disorders

Keyword Definitions:

• Asthma: Chronic inflammatory disorder of the airways causing wheezing, shortness of breath, and bronchial hyperresponsiveness.

• Emphysema: Chronic lung disease characterized by destruction of alveolar walls, decreased respiratory surface, and air trapping.

• Respiratory surface: Area of alveoli available for gas exchange.

• Bronchioles: Small airways in the lungs branching from bronchi.

• Inflammation: Tissue response to injury or infection, causing swelling and irritation.

• Chronic lung disorder: Persistent lung condition affecting breathing and gas exchange.

Lead Question - 2018

Which of the following options correctly represents the lung conditions in asthma and emphysema, respectively :

(A) Decreased respiratory surface; Inflammation of bronchioles

(B) Inflammation of bronchioles; Decreased respiratory surface

(C) Increased respiratory surface; Inflammation of bronchioles

(D) Increased number of bronchioles; Increased respiratory surface

Explanation:

Answer is (B). Asthma is characterized by inflammation of bronchioles causing airway narrowing and difficulty in breathing. Emphysema involves destruction of alveolar walls, reducing respiratory surface area, leading to impaired gas exchange. Both conditions affect lung function, but the primary pathological features differ as indicated.

Guessed Questions for NEET UG:

1) Single Correct: The main cause of airway obstruction in asthma is:

(A) Alveolar wall destruction

(B) Bronchial inflammation and constriction

(C) Pleural effusion

(D) Pulmonary fibrosis

Explanation:

Answer is (B). In asthma, inflammation and smooth muscle constriction of bronchioles narrow the airways, causing wheezing, shortness of breath, and reduced airflow.

2) Single Correct: Which of the following occurs in emphysema?

(A) Increased alveolar surface

(B) Destruction of alveolar walls

(C) Bronchospasm

(D) Mucus hypersecretion

Explanation:

Answer is (B). Emphysema destroys alveolar walls, decreasing surface area for gas exchange, causing hypoxia, hypercapnia, and difficulty in breathing.

3) Single Correct: Clinical sign common in asthma patients is:

(A) Barrel chest

(B) Wheezing

(C) Cyanosis without dyspnea

(D) Clubbing of fingers

Explanation:

Answer is (B). Wheezing occurs due to turbulent airflow in narrowed bronchioles during asthma attacks, a key diagnostic symptom.

4) Assertion-Reason:

Assertion: Emphysema reduces the respiratory surface of lungs.

Reason: Alveolar wall destruction and air trapping occur.

(A) Both true, Reason correct

(B) Both true, Reason incorrect

(C) Assertion true, Reason false

(D) Both false

Explanation:

Answer is (A). Emphysema involves destruction of alveoli walls, decreasing surface area and causing air trapping, directly explaining reduced respiratory surface for gas exchange.

5) Single Correct: Which diagnostic test measures airflow obstruction in asthma?

(A) Spirometry

(B) X-ray

(C) CT scan

(D) MRI

Explanation:

Answer is (A). Spirometry measures forced expiratory volume and capacity, helping assess bronchial obstruction in asthma.

6) Single Correct: Which type of emphysema primarily affects upper lobes of lungs?

(A) Panacinar

(B) Centriacinar

(C) Paraseptal

(D) Irregular

Explanation:

Answer is (B). Centriacinar emphysema predominantly affects respiratory bronchioles in upper lobes, commonly associated with smoking.

7) Matching Type:

Column I | Column II

a. Asthma | i. Decreased alveolar surface

b. Emphysema | ii. Bronchial inflammation and narrowing

c. Chronic bronchitis | iii. Mucus hypersecretion

(A) a-ii, b-i, c-iii

(B) a-i, b-ii, c-iii

(C) a-iii, b-ii, c-i

(D) a-ii, b-iii, c-i

Explanation:

Answer is (A). Asthma features bronchial inflammation, emphysema reduces alveolar surface, and chronic bronchitis involves excessive mucus secretion causing airflow limitation.

8) Fill in the Blank:

______ is characterized by destruction of alveolar walls and decreased respiratory surface.

(A) Asthma

(B) Emphysema

(C) Chronic bronchitis

(D) Pneumonia

Explanation:

Answer is (B). Emphysema destroys alveolar walls, reducing the surface area for gas exchange, leading to chronic breathing difficulty.

9) Choose the correct statements:

(i) Asthma involves reversible airway obstruction.

(ii) Emphysema is associated with permanent alveolar damage.

(iii) Both conditions cause decreased respiratory surface.

(A) i and ii only

(B) i and iii only

(C) ii and iii only

(D) i, ii, iii

Explanation:

Answer is (A). Asthma has reversible obstruction, emphysema involves permanent alveolar damage. Decreased respiratory surface is mainly in emphysema, not asthma.

10) Clinical-type: A patient presents with prolonged expiration, wheezing, and difficulty in airflow reversal. Likely condition is:

(A) Emphysema

(B) Asthma

(C) Pulmonary fibrosis

(D) Pneumothorax

Explanation:

Answer is (B). Wheezing and airflow obstruction with reversibility suggest asthma. Emphysema shows chronic alveolar destruction and barrel chest, but wheezing is less prominent.

Subtopic: Occupational Respiratory Disorders

Keyword Definitions:

• Occupational respiratory disorder: Lung diseases caused by workplace exposure to dust, chemicals, or fumes.

• Emphysema: Chronic lung condition with alveolar destruction, reducing gas exchange.

• Anthracis: Infection caused by Bacillus anthracis, primarily affecting the skin and lungs.

• Botulism: Neuroparalytic disease caused by Clostridium botulinum toxin.

• Silicosis: Lung fibrosis caused by inhalation of silica dust, common in mining or stone cutting.

• Respiratory system: Organs involved in gas exchange including lungs, bronchi, and alveoli.

Lead Question - 2018

Which of the following is an occupational respiratory disorder :

(A) Emphysema

(B) Anthracis

(C) Botulism

(D) Silicosis

Explanation:

Answer is (D). Silicosis is caused by prolonged inhalation of silica dust at workplaces like mines and quarries. It leads to lung fibrosis, reduced respiratory efficiency, and chronic breathing problems. Other options are either infectious diseases (Anthracis, Botulism) or non-occupational chronic conditions (Emphysema).

Guessed Questions for NEET UG:

1) Single Correct: Chronic inhalation of coal dust causes:

(A) Emphysema

(B) Pneumoconiosis

(C) Asthma

(D) Bronchitis

Explanation:

Answer is (B). Pneumoconiosis is caused by inhalation of coal dust, leading to fibrosis of lungs. Occupational exposure in coal mines is the primary cause.

2) Single Correct: Farmer’s lung is caused by exposure to:

(A) Silica dust

(B) Moldy hay

(C) Asbestos

(D) Lead fumes

Explanation:

Answer is (B). Farmer’s lung is hypersensitivity pneumonitis caused by inhaling spores of moldy hay, affecting alveoli and causing chronic inflammation.

3) Single Correct: Which occupational lung disease is associated with asbestos exposure?

(A) Byssinosis

(B) Silicosis

(C) Asbestosis

(D) Anthracosis

Explanation:

Answer is (C). Asbestosis is fibrosis of lungs due to prolonged inhalation of asbestos fibers, leading to restrictive lung disease and increased cancer risk.

4) Assertion-Reason:

Assertion: Emphysema can be caused by occupational exposure.

Reason: It results from inhaling toxic dust or smoke over long periods.

(A) Both true, Reason correct

(B) Both true, Reason incorrect

(C) Assertion true, Reason false

(D) Both false

Explanation:

Answer is (A). Occupational exposure to dust, fumes, and smoke can induce emphysematous changes by destroying alveolar walls, making the assertion and reason correct.

5) Single Correct: Which occupation has highest risk of silicosis?

(A) Textile workers

(B) Miners