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Q1. Which of the following is the cofactor of carbonic anhydrase?   

• 1) Fe  
• 2) Cu  
• 3) Zn  
• 4) Mg  

Solution

Carbonic anhydrase is a zinc-activated enzyme, so its cofactor is zinc.  

Q2. Haemoglobin is a

• 1) Fat
• 2) Reproductive pigment
• 3) Carbohydrate
• 4) Respiratory pigment

Solution

Haemoglobin is a respiratory pigment which binds with oxygen to form oxyhaemoglobin and is then transported to various body cells for respiration.

Q3. The vital capacity of the lungs includes   

• 1) IRV + TV + ERV  
• 2) RV + ERV + TV + IRV  
• 3) ERV + TV  
• 4) IRV + TV  
• 5) ERV + RV  

Solution

The vital capacity is the total of the tidal volume, inspiratory reserve volume and expiratory reserve volume.  

Q4. What is the average breathing rate in a healthy human?

Solution

The average breathing rate in a healthy human is 12-16 times per minute.

Q5. It is known that exposure to carbon monoxide is harmful to animals because   

• 1) In increases CO₂ transport.  
• 2) It destroys haemoglobin.  
• 3) It reduces CO₂ transport.  
• 4) It reduces O₂ transport.  

Solution

Carbon monoxide is harmful to animals because it combines more readily with haemoglobin than oxygen forming the stable compound carboxyhaemoglobin and thus destroys free haemoglobin.   

Q6. Name the muscles present between the ribs which generate the pressure gradients in lungs.

Solution

External and internal intercostal muscles

Q7. In Hamburger’s phenomena, which ion is transported?

• 1) K⁺
• 2) Cl⁻
• 3) Mg⁺⁺
• 4) Na⁺

Solution

The movement of chloride ions is called the chloride shift or Hamburger phenomenon. Chloride ions diffuse from the plasma into the erythrocytes to restore the ionic balance when the bicarbonate ions are transported during carbon dioxide transport.

Q8. State the two stages involved in breathing. Name the components which help in adjusting the volume of the thoracic chamber.

Solution

Two stages involved in breathing are  Inspiration: Atmospheric air is drawn inside the body. Expiration: Alveolar air is released out of the body. The diaphragm and internal and external intercostal muscles help in adjusting the volume of the thoracic chamber.

Q9. Name the three layers which constitute the diffusion membrane.

Solution

The three layers of the diffusion membrane are Thin squamous epithelium of alveoli Endothelium of alveolar capillaries Basement membrane or substance present between the squamous epithelium of alveoli and the endothelium of alveolar capillaries

Q10. Mosquito receives air through   

• 1) Cilia  
• 2) Flagellum  
• 3) None of the above  
• 4) Pedicel  

Solution

The mosquito receives air through spiracles which enters the trachea and transports the respiratory gases into the body cells.   

Q11. Name the two blood vessels which recognise the changes in H⁺ ions and CO₂.

Solution

Aortic arch and carotid artery

Q12. Respiratory quotient is defined as   

• 1)  
• 2)  
• 3)  
• 4)

Solution

Respiratory quotient is defined as the ratio of the volume of carbon dioxide produced to the volume of oxygen consumed over a period of time in respiration.  

Q13. In breathing movements, the air volume can be estimated by   

• 1) Stethoscope  
• 2) Spirometer  
• 3) Sphygmomanometer  
• 4) Hygrometer  

Solution

A spirometer is an instrument used for recording the changes in the volume of air in and out of the lungs. This process is called spirometry.   

Q14. Alveoli become enlarged and damaged with reduced surface area in heavy smokers. The condition is called   

• 1) Bronchitis  
• 2) Silicosis  
• 3) Asthma  
• 4) Emphysema  

Solution

In Emphysema, over inflation of the alveoli and rupture of alveolar walls occur. This decreases the surface area and pulmonary ventilation.   

Q15. How much percent of CO₂ is present in expired air? 

• 1) 7%
• 2) 5.3%
• 3) 0.04%
• 4) 3.6%

Solution

3.6% of CO2 is present in expired air when the partial pressure is 32 mm Hg. 

Q16. The amount of volume of air which can be inspired/expired normally is called   

• 1) Tidal volume  
• 2) Vital capacity  
• 3) Normal volume  
• 4) Residual volume  

Solution

Tidal volume is the volume of air normally inspired or expired in one breath without any effort. It is about 500 ml in the average human adult male.   

Q17. RQ of fat is

• 1) Less than one
• 2) One
• 3) Infinite
• 4) More than one

Solution

The ratio of the volume of carbon dioxide produced to the volume of oxygen used in a unit time is called respiratory quotient (RQ). The fats are hydrolysed to glycerol and fatty acids. The fatty acids are poor in oxygen, so they require more oxygen for their complete oxidation. Therefore, the absorption of oxygen is more than the liberation of carbon dioxide, and thus, RQ becomes less than unity.

Q18. The oxygen dissociation curve is

• 1) Hyperbolic
• 2) Parabolic
• 3) Straight
• 4) Sigmoid

Solution

An oxygen dissociation curve is the graph showing the percent saturation of haemoglobin with the changes in partial pressure of oxygen at constant pH. The curve shows that there is a progressive increase in the percent saturation of haemoglobin with the increase in partial pressure of oxygen up to a level, and then it becomes constant. So, a normal oxygen dissociation curve is sigmoid.

Q19. Name the part of the CNS which regulates the functions of the respiratory rhythm centre.

Solution

Pneumotaxic centre

Q20. The term ‘Glycolysis’ has originated from the Greek words 

• 1) Glucose and lysis
• 2) Glyco and lysis
• 3) Glycose and lysis
• 4) Glycos and lysis

Solution

The term ‘Glycolysis’ has originated from the Greek words ‘glycos’ and ‘lysis’. ‘Glycos’ means sugar and ‘lysis’ means splitting. 

Q21. Name the process by which oxygen is taken in and carbon dioxide is released into the atmosphere.

Solution

Pulmonary ventilation (breathing)

Q22. The alveoli of lungs are lined by

• 1) Cuboidal epithelium
• 2) Squamous epithelium
• 3) Simple epithelium
• 4) Columnar epithelium
• 5) Ciliated epithelium

Solution

Squamous epithelium forms the delicate lining of cavities such as the alveoli of lungs, mouth, pericardium, oesophagus and nose. It is made of thin, flat, irregular shaped cells which fit together like floor tiles to form compact tissues. 

Q23. What is tidal volume?

Solution

Tidal volume is the volume of air inspired or expired during normal respiration.

Q24. Increased asthmatic attacks in certain seasons are related to

• 1) Eating fruits preserved in containers
• 2) Inhalation of seasonal pollen
• 3) Low temperature
• 4) Hot and humid environment

Solution

Increased asthmatic attacks in certain seasons are related to inhalation of pollen grains of plants (e.g. congress plant). Asthma is characterised by narrowing and inflammation of bronchi, bronchospasm and difficulty in breathing.

Q25. In humans, which among these is not a step in respiration?  

• 1) Pulmonary ventilation  
• 2) Alveolar diffusion of O₂ and CO₂  
• 3) Diffusion of O₂ and CO₂ between blood and tissues  
• 4) Utilisation of CO₂ by cells for catabolic reactions  
• 5) Transport of gases by blood  

Solution

In humans, respiration involves the following steps:     Pulmonary ventilation Alveolar diffusion of O₂ and CO₂ Transport of gases by blood Diffusion of O₂ and CO₂ between blood and tissues Utilisation of O₂ by cells for catabolic reactions and the resultant release of CO₂

Q26. Respiration results in 

• 1) Release of O₂
• 2) Anabolism
• 3) Release of CO₂
• 4) Transfer of CO₂

Solution

Respiration is a catabolic process which involves uptake of oxygen by tissue cells, oxidation of food by oxidising enzymes inside the cells and release of carbon dioxide from body tissues.

Q27. A is using maximum capacity to inhale as well as to exhale. What is the term which can be used for the volume of air exhaled by A.

Solution

Vital capacity

Q28. What is true about haemoglobin?   

• 1) None of the above  
• 2) It contains a carbohydrate part called globin.  
• 3) It contains four pyrrole rings attached to iron element at the centre.  
• 4) It contains six pyrrole rings attached to iron element at the centre.  

Solution

Haemoglobin is formed of four iron-containing porphyrin prosthetic groups attached to a globin protein. Each porphyrin molecule is formed at four pyrrole rings attached to iron element at the centre.  

Q29. The total number of alveoli in both lungs are 

• 1) 3000 billion
• 2) 3000 million
• 3) 300 billion
• 4) 300 million

Solution

There are about 300 million alveoli in both the lungs which increase the surface area for the exchange of respiratory gases.

Q30. Binding of oxygen with haemoglobin tends to displace carbon dioxide from the blood. This phenomenon is called  

• 1) Hamburger shift  
• 2) Chloride shift  
• 3) Haldane effect  
• 4) None of the above  

Solution

Binding of oxygen with haemoglobin tends to displace carbon dioxide from the blood. This phenomenon is called Haldane effect. It occurs because the combination of oxygen with haemoglobin causes it to become a stronger acid which, in turn, displaces carbon dioxide from the blood.  

Q31. Severe acute respiratory syndrome (SARS)  

• 1) Is an acute form of asthma  
• 2) Affects non-vegetarians much faster than vegetarians  
• 3) Is caused by a variant of the common cold virus (corona virus)  
• 4) Is caused by a variant of Pneumococcus pneumonae  

Solution

Severe acute respiratory syndrome (SARS) is caused by human coronavirus. It spreads through contact, respiratory secretions and cockroaches. The main symptoms include cold, dry cough, headache, loss of appetite and fever.   

Q32. What is partial pressure? What are the symbols used to denote the partial pressures of oxygen and carbon dioxide?

Solution

Partial pressure is the pressure contributed by the individual gas in a mixture of gases. Symbols used to denote the partial pressure of oxygen and carbon dioxide are pO₂ and pCO₂.

Q33. Dead space air in man is  

• 1) 250 ml  
• 2) 1.5 l  
• 3) 500 ml  
• 4) 150 ml  

Solution

Of 500 ml of inspired air, only 350 ml of fresh air reaches the lung alveoli and is called alveolar volume while about 150 ml of inspired air remains in the respiratory tract which is called anatomical dead space volume.  

Q34. The chloride shift occurs in response to  

• 1) HCO₃⁻  
• 2) H⁺  
• 3) Na⁺  
• 4) K⁺  

Solution

The chloride shift occurs in response to bicarbonate ions (HCO₃⁻). Most of the bicarbonate ions diffuse into the plasma of the blood during the transport of carbon dioxide. To restore the ionic balance, equal amounts of chloride ions diffuse inside the RBCs from the plasma. The exchange of bicarbonate ions of RBCs and chloride ions of the plasma is called the chloride shift or Hamburger shift.  

Q35. Hamburger shift is also known as  

• 1) Potassium shift  
• 2) Bicarbonate shift  
• 3) Chloride shift  
• 4) All of the above  

Solution

The exchange of bicarbonate ions of RBCs and chloride ions of plasma is called the Hamburger shift or chloride shift.   

Q36. The majority of carbon dioxide produced by our body cells is transported to the lungs 

• 1) As bicarbonates
• 2) Attached to haemoglobin
• 3) As carbonates
• 4) Dissolved in the blood

Solution

About 70% of carbon dioxide is transported from the body tissues to the lungs as sodium and potassium bicarbonates.

Q37. Which one of the following mammalian cells is not capable of metabolising glucose to carbon dioxide aerobically?  

• 1) Unstriated muscle cells  
• 2) White blood cells  
• 3) Red blood cells  
• 4) Liver cells  

Solution

Red blood cells are not capable of metabolising glucose to carbon dioxide aerobically because they lack mitochondria which are the sites of aerobic respiration.  

Q38. Book lungs are respiratory organs of   

• 1) Earthworm  
• 2) Mollusca  
• 3) Mammals  
• 4) Arachnida  

Solution

Arachnida are Arthropods which have jointed legs. These include spiders, scorpions, ticks and mites. The respiratory organs of Arachnida are book lungs.   

Q39. Represent the human respiratory system diagrammatically.

Solution

Human respiratory system:  

Q40. Name the kind of volume the following components constitute: TV + IRV RV + ERV + TV + IRV TV + ERV ERV + RV

Solution

TV + IRV - Inspiratory capacity (IC) RV + ERV + TV + IRV - Total lung capacity TV + ERV - Expiratory capacity ERV + RV - Functional residual capacity

Q41. The breathing rate in humans is controlled by 

• 1) Cerebellum
• 2) Medulla oblongata
• 3) Thalamus
• 4) Hypothalamus

Solution

The breathing rate in human is controlled by the medulla oblongata in which inspiratory and expiratory centres are located.   The inspiratory centre or dorsal respiratory group (DRG) causes inspiration. The expiratory centre or ventral respiratory group (VRG) causes either inspiration or expiration depending on which neurons in the group are stimulated.

Q42. The enzyme essential for the transport of CO₂ as bicarbonate in the blood is   

• 1) Thrombokinase  
• 2) Succinic dehydrogenase  
• 3) Carboxypeptidase  
• 4) Carbonic anhydrase  
• 5) Lactase  

Solution

Carbonic anhydrase is an essential enzyme used for the transport of CO₂ as bicarbonate in the blood. It is stimulated by the low partial pressure of oxygen at the cellular level.    

Q43. Write the effects of the following disorders on the human body:     Asthma   Emphysema

Solution

Asthma - Difficulty in breathing, inflammation of bronchi and bronchioles   Emphysema - Alveolar walls get damaged reducing the respiratory surface

Q44. The bulk of CO₂ released from body fluids into the blood is present as   

• 1) Carbaminohaemoglobin in RBCs  
• 2) Bicarbonate in blood plasma and RBCs  
• 3) Free CO₂ in blood plasma  
• 4) 70% as carbaminohaemoglobin and 30% as bicarbonate  

Solution

About 70% of carbon dioxide released by respiring tissue cells diffuses into the plasma and then into red blood cells, where it combines with water to form carbonic acid.  

Q45. About 97% of O₂ is transported by RBCs. The remaining 3%  

• 1) Is inside the mitochondria
• 2) Remains in the lungs
• 3) Is dissolved in plasma and transported
• 4) Is in peroxisomes
• 5) Is attached to cell membranes

Solution

About 1-3% of oxygen is transported by the blood in the dissolved form in blood plasma.

Q46. Oxygen-carrying capacity of human blood is reduced due to the pollution of

• 1) SO₂
• 2) O₃
• 3) CO₂
• 4) CO

Solution

The oxygen-carrying capacity of human blood is reduced due to carbon monoxide poisoning. CO combines more readily with haemoglobin than oxygen, forming a stable compound, carboxyhaemoglobin, which reduces the amount of free haemoglobin available for carrying oxygen.

Q47. The pharynx opens into the larynx by a slit-like aperture called  

• 1) Bronchus  
• 2) Epiglottis  
• 3) Glottis  
• 4) Trachea  

Solution

The pharynx opens into the larynx by a slit-like aperture called the glottis, which is covered by a cartilaginous flap called the epiglottis. The epiglottis closes the glottis to prevent the entry of food particles during swallowing.  

Q48. Oxygen is carried by 

• 1) Platelets
• 2) Erythrocytes
• 3) None of the above
• 4) Leucocytes

Solution

Erythrocytes or RBCs are capable of binding oxygen as it has a haemoglobin pigment which contains a haem part and a protein part in its structure. The haem part of the haemoglobin structure contains four atoms of iron, each capable of combining with a molecule of oxygen. Oxygen combines with haemoglobin to form oxyhaemoglobin and is carried to different body cells. 

Q49. Explain diagrammatically the mechanism of breathing and the positions of ribs, diaphragms and the thoracic cavity during inspiration and expiration.  

Solution

Mechanism of breathing - inspiration:           Mechanism of breathing - expiration:        

Q50. State the name of the form in which CO₂ is transported by blood.

Solution

Carbaminohaemoglobin

Q51. State the significance of the sigmoid oxygen dissociation curve.

Solution

The sigmoid oxygen dissociation curve is useful in studying the effects of factors such as H⁺ ion concentration and pCO₂ on binding of oxygen with haemoglobin.

Q52. The partial pressure of oxygen in the lungs is 

• 1) 100 mm Hg
• 2) 110 mm Hg
• 3) 60 mm Hg
• 4) 40 mm Hg

Solution

The partial pressure of oxygen in the lungs or alveolar air is approximately 100 mm Hg, while that of oxygen in the venous blood in pulmonary arterial capillaries is 40 mm Hg on an average. Due to a PO₂ difference between air and blood, oxygen diffuses rapidly from the alveolar air into the blood. 

Q53. The lungs are enclosed in a covering called 

• 1) Pericardium
• 2) Peritoneum
• 3) Pleural membrane
• 4) Perichondrium

Solution

Each lung is enclosed by a thin, transparent, two-layered membrane called the pleural membrane. The inner membrane is called visceral pleuron and the outer membrane is called parietal pleuron. Between these two membranes, a cavity called the pleural cavity is present which is filled with a watery fluid called the pleural fluid.

Q54. Name one disorder caused by cigarette smoking.

Solution

Emphysema

Q55. Which part of the human respiratory system serves as the common passage for food and air?

Solution

Nasopharynx

Q56. Name the instrument used to measure pulmonary volume.

Solution

Spirometer

Q57. In which parts of the central nervous system is the respiratory rhythm centre located?

Solution

Medulla oblongata

Q58. The respiratory centre of the brain is sensitive to   

• 1) All of the above  
• 2) Accumulation of blood in the brain  
• 3) More O₂ concentration in blood  
• 4) More CO₂ concentration in blood  

Solution

An increase in the carbon dioxide concentration in the blood stimulates the inspiratory and expiratory centres through increased formation and dissociation of carbonic acid and increased concentration of H⁺, which lowers the pH of blood and results in acidosis.  

Q59. After deep inspiration, maximum expiration of lungs is called 

• 1) Vital capacity
• 2) Total lung capacity
• 3) Inspiratory capacity
• 4) Functional residual capacity

Solution

The maximum volume of air a person can breathe in after a forced expiration or the maximum volume of air a person can breathe out after a forced inspiration is called vital capacity.

Q60. Identify the following structures of the human respiratory system:     Double membrane which covers the lungs   Sac-like structures which are in close contact with the capillary network   Structure which helps in producing sound   Region where the nasopharynx opens through the glottis

Solution

Double membrane which covers the lungs - Pleura   Sac-like structures which are in close contact with the capillary network - Alveoli   Structure which helps in producing sound - Larynx   Region where the nasopharynx opens through the glottis - Trachea

Q61. The pneumotaxic centre is present in  

• 1) Pons varolii  
• 2) Cerebellum  
• 3) Cerebrum  
• 4) Medulla  

Solution

The pneumotaxic centre is present in the dorsal part of pons varolii. Its main function is to limit inspiration.  

Q62. 1200 ml volume of air which always remains in the lungs even after forcible expiration is called  

• 1) Residual volume  
• 2) Vital capacity  
• 3) Tidal volume  
• 4) Inspiratory volume  

Solution

Residual volume is the volume of air which always remains in the lungs even after forcible expiration. It is about 1100-1200 ml.  

Q63. Name the process used by comb jellies for the exchange of gases during respiration.

Solution

Diffusion

Q64. A person breathes in some volume of air by forced inspiration after having a forced expiration. This quantity of air taken in is   

• 1) Total lung capacity  
• 2) Vital capacity  
• 3) Inspiratory capacity  
• 4) Tidal volume  

Solution

A person breathes in some volume of air by forced inspiration after having a forced expiration. This quantity of air taken in is the total lung capacity. It is equal to the sum of the vital capacity and the residual volume.   

Q65. Which one of the following can bind several hundred times more strongly to the haemoglobin than oxygen?  

• 1) SO₂  
• 2) CO  
• 3) H₂CO₃  
• 4) CO₂  

Solution

CO (carbon monoxide) can bind several hundred times more strongly to haemoglobin than oxygen forming the stable compound carboxyhaemoglobin. This reduces the amount of free haemoglobin available for carrying O₂.   

Q66. Residual volume is 

• 1) Greater than inspiratory volume
• 2) Lesser than tidal volume
• 3) Greater than vital capacity
• 4) Greater than tidal volume

Solution

Residual volume is always greater than tidal volume. Tidal volume is the volume of air normally inspired or expired in one breath without any effort, and the residual volume of air is the air which remains in the lungs even after forcible expiration. Tidal volume is about 500 ml, whereas residual volume is about 1100-1200 ml. 

Q67. During hibernation, the frog respires through   

• 1) Lungs  
• 2) Tympanum  
• 3) Integument  
• 4) Gills  

Solution

During hibernation, cutaneous respiration occurs in the frog, i.e. it respires through its moist skin or integument. The skin is permeable to respiratory gases and carries oxygen to the body cells for respiration.   

Q68. Represent diagrammatically the exchange of gases at the alveolar level and the tissue level.  

Solution

   

Q69. In which of the following animals, respiration occurs without any respiratory organ?   

• 1) Earthworm  
• 2) Cockroach  
• 3) Fish  
• 4) Frog  

Solution

The earthworm breathes through its thin and moist skin.     Oxygen is absorbed and transported to all the cells of the body where it is utilised for respiration.  

Q70. The volume of air which remains in the conducting airways and is not available for gas exchange is called

• 1) Forced expiratory volume
• 2) Anatomic dead space
• 3) Functional residual capacity
• 4) Vital capacity

Solution

The volume of air which remains in the conducting airways and is not available for gas exchange is called anatomic dead space. It is approximately 150 ml. 

Q71. Name the region present in the central nervous system which regulates respiration.

Solution

Respiratory rhythm centre

Q72. Distinguish between IRV and ERV.  

Solution

IRV (Inspiratory Reserve Volume)     ERV (Expiratory Reserve Volume)     It is the additional volume of air which a person can inhale during forcible inspiration.   It is the additional volume of air which a person expires during forcible expiration.   It averages 2500 to 3000 ml.    It averages 1000 to 1100 ml.      

Q73. Name the enzyme which is present in high quantities in RBCs.

Solution

Carbonic anhydrase

Q74. Name the following: Volume of air which remains in the lungs after normal expiration Total volume of air a person can inspire after normal expiration

Solution

Volume of air which remains in the lungs after normal expiration - Inspiratory capacity (IC) Total volume of air a person can inspire after normal expiration - Functional residual capacity (FRC)

Q75. In the kidneys, a blood vessel has pCO₂ = 45 mm Hg, which is lower than the kidney tissues. What will be the direction of the diffusion of blood?

Solution

The direction of diffusion of blood will be from the kidney tissue to the blood vessel.

Q76. Regarding the functions of our respiratory system, mark the wrong entry.   

• 1) Warms up the air  
• 2) Diffusion of gases  
• 3) All of the above  
• 4) Humidifies the air  

Solution

Nasal chambers help in moistening or humidifying the air with evaporated mucous. It also helps in warming up the air by heat radiated by the blood. Diffusion of respiratory gases also occurs by the respiratory system.   

Q77. One molecule of haemoglobin carries how many molecules of oxygen?  

• 1) Eight
• 2) Two
• 3) Four
• 4) Six

Solution

One molecule of haemoglobin carries four molecules of oxygen. The haem part of the haemoglobin structure contains four atoms of iron, each capable of combining with a molecule of oxygen. 

Q78. One reason for emphysema is

• 1) drug addiction
• 2) heavy exercise
• 3) smoking
• 4) liquor consumption

Solution

Cigarette smoking is by far the biggest culprit for people developing emphysema, and it is also the most preventable cause

Q79. What does RV stand for? What is the average RV for a healthy person?

Solution

Residual volume. The average RV for a healthy person is 1100 to 1200 ml.

Q80. Name the animal which uses its moist cuticle as a respiratory organ.

Solution

Earthworm

Q81. Emphysema is a

• 1) Pulmonary disease
• 2) Cardiovascular disease
• 3) Renal disease
• 4) Neural disease

Solution

Emphysema is a pulmonary disease. It is due to the inflation or abnormal distension of the bronchiole or alveolar sac resulting in the loss of elasticity of lungs.

Q82. Name the structure which divides into the right and left bronchiole.

Solution

Trachea

Q83. Describe the process of expiration.

Solution

When the diaphragm and intercostal muscles are relaxed, the thoracic chamber comes to its normal volume. This reduces the pulmonary volume. This results in an increase in the intra-pulmonary pressure in the lungs than the atmospheric pressure causing the expulsion of air from the lungs.

Q84. Blood analysis of a patient reveals an unusually high quantity of carboxyhaemoglobin content. Which of the following conclusions is most likely to be correct? The patient has inhaled polluted air containing high content of 

• 1) Carbon disulphide
• 2) Carbon monoxide
• 3) Chloroform
• 4) Carbon dioxide

Solution

The patient has inhaled polluted air containing a high content of carbon monoxide. Carbon monoxide combines more readily with haemoglobin than oxygen. It forms a stable compound, carboxyhaemoglobin, which reduces the amount of free haemoglobin available for carrying oxygen and starves the tissues of oxygen. Deficiency of oxygen causes headache, dizziness, nausea, paralysis and even death.

Q85. Which of the following statements is correct?   

• 1) Cyanosis means collapse of alveoli  
• 2) Coryza is caused by human corona virus  
• 3) Eupnoea means slow breathing  
• 4) During inspiration, external intercostal muscles and diaphragm contract  

Solution

During inspiration, the external intercostal muscles contract and pull the ribs and sternum upwards and outwards, thus increasing the volume of the thoracic cavity.     The diaphragm contracts and becomes flat, thereby increasing the volume of the thoracic cavity.   

Q86. State the functions of the following: Conducting part Exchange part

Solution

Conducting part - The conducting part transports atmospheric air to the alveoli. It humidifies and brings air to body temperature. It clears the air from foreign particles. Exchange part - It allows the diffusion of oxygen and carbon dioxide between blood and atmospheric air.

Q87. Name the muscles which increase the volume of the thoracic chamber.  

Solution

External intercostal muscles  

Q88. How is the oxygen dissociation curve obtained? State the factors favourable for the binding of oxygen with haemoglobin.

Solution

The oxygen dissociation curve is obtained by plotting the percentage saturation of haemoglobin with oxygen against pO₂. Factors favourable for the binding of oxygen with haemoglobin at the alveolar level are High partial pressure of oxygen Low partial pressure of carbon dioxide Low concentration of H⁺ ions Low temperature

Q89. Where is the pneumotaxic region located in the brain?

Solution

Pons

Q90. Explain pneumotaxic centre.

Solution

It lies in pons Varoli. When stimulated, it increases the rate of respiration but decreases the depth of respiration. It causes evaporation of water from the respiratory membrane. This gives cooling effect.

Q91. How does the diaphragm help in inspiration?  

Solution

When the intra-pulmonary pressure, i.e. the pressure within the lungs, is lesser than the atmospheric pressure, the diaphragm contracts.     The contraction of the diaphragm increases the volume of the thoracic chamber, thus increasing space for more air which is withdrawn during inspiration.     Hence, the person is able to inspire.  

Q92. Pulmonary tuberculosis is caused by

• 1) Corona virus
• 2) Mycobacterium tuberculosis
• 3) Corynebacterium diphtheriae
• 4) Rhinovirus

Solution

Pulmonary tuberculosis (TB) is caused by Mycobacterium tuberculosis. It affects the lungs and the pleura. The bacteria destroy parts of the lung tissue, and the tissue is replaced by fibrous connective tissue.

Q93. What is total lung capacity?

Solution

Total lung capacity is the total volume of air accommodated in lungs at the end of forced inspiration.

Q94. How do the epiglottis and uvula differ in their role?

Solution

Epiglottis closes the glottis and the uvula covers the internal nares during swallowing so that food enters the oesophagus only.

Q95. Draw a well-labelled diagram of the section of an alveolus and the pulmonary capillary.  

Solution

   

Q96. What are the factors which interfere with the formation of oxyhaemoglobin?

Solution

Factors which interfere with the formation of haemoglobin are Partial pressure of CO₂ Concentration of hydrogen ions Temperature

Q97. Name the respiratory organs of insects.

Solution

Tracheal tubes

Q98. Write the term for the additional volume of air which a person can forcibly inspire?

Solution

Inspiratory reserve volume (IRV)

Q99. Distinguish between vital capacity and total lung capacity.

Solution

Vital Capacity Total Lung Capacity It is the maximum volume of air a person can breathe in after forced expiration. It is the total volume of air accommodated in the lungs at the end of forced inspiration. It includes expiratory reserve volume, tidal volume and inspiratory reserve volume. It includes the residual volume and the vital capacity (ERV + TV + IRV)  

Q100. State the significance of the larynx.

Solution

The larynx is responsible for sound production.

Q101. Mention the two factors which can affect the rate of diffusion of oxygen and carbon dioxide during respiration.  

Solution

The two factors which can affect the rate of diffusion of oxygen and carbon dioxide during respiration are as follows:     Solubility of gases   Thickness of the membranes involved in diffusion

Q102. Write the respiratory organs of the following organisms: Tadpole larvae Shark Planaria Cockroach

Solution

Tadpole larva - Gills Shark - Gills Planaria - Body surface Cockroach - Tracheal tubes

Q103. Oxygen binds to haemoglobin at the lung surface and dissociates at the tissues. Justify.  

Solution

For the formation of oxyhaemoglobin, the factors required such as high pO₂, low pCO₂, low concentration of H⁺ ions and low temperature are maintained in the alveoli. Hence, the binding of oxygen with haemoglobin at lung surfaces is faster.     Low pO₂, high pCO₂, high H+ ion concentration and high temperature are the factors found in tissues which always favour the dissociation of oxygen.  

Q104. Where is carbonic anhydrase found? Write the reaction it catalyses.  

Solution

Carbonic anhydrase is found in RBCs. It catalyses the following reaction:    

Q105. State the primary site of exchange of gases in lungs.

Solution

Alveoli

Q106. What is fibrosis and how is it caused?  

Solution

Fibrosis is the uncontrolled proliferation of fibrous tissue which causes serious lung damage. Long exposure to dust particles weakens the defence mechanism of the body causing fibrosis.  

Q107. What is residual volume? What is its significance?

Solution

Residual volume is the volume of air remaining in the lungs even after forcible expiration. By adding a few respiratory volumes, pulmonary capacities can be derived which help in clinical diagnosis.