Q1: Define vital capacity. What is its significance?
Ans: Vital capacity is the maximum volume of air that can be exhaled after a maximum inspiration. It is about 3.5 – 4.5 litres in the human body. It promotes the act of supplying fresh air and getting rid of foul air, thereby increasing the gaseous exchange between the tissues and the environment.
Vital Capacity Curve
Q2: State the volume of air remaining in the lungs after a normal breathing.
Ans: The volume of air remaining in the lungs after a normal expiration is known as functional residual capacity (FRC). It includes expiratory reserve volume (ERV) and residual volume (RV). ERV is the maximum volume of air that can be exhaled after a normal expiration. It is about 1000 mL to 1500 mL. RV is the volume of air remaining in the lungs after maximum expiration. It is about 1100 mL to 1500 mL.
∴ FRC = ERV RV
≅ 1500 1500
≅ 3000 mL
Functional residual capacity of the human lungs is about 2500 – 3000 mL.
Q3: Diffusion of gases occurs in the alveolar region only and not in the other parts of respiratory system. Why?
Ans:
Q4: What are the major transport mechanisms for CO2? Explain.
Ans: Plasma and red blood cells transport carbon dioxide. This is because they are readily soluble in water.
(1) Through plasma: About 7% of CO2 is carried in a dissolved state through plasma. Carbon dioxide combines with water and forms carbonic acid.
Since the process of forming carbonic acid is slow, only a small amount of carbon dioxide is carried this way.
(2) Through RBCs: About 20 – 25% of CO2 is transported by the red blood cells acarbaminohaemoglobin. Carbon dioxide binds to the amino groups on the polypeptide chains of haemoglobin and forms a compound known as carbaminohaemoglobin.
Transportation of CO2 through RBCs
(3) Through sodium bicarbonate: About 70% of carbon dioxide is transported as sodium bicarbonate. As CO2 diffuses into the blood plasma, a large part of it combines with water to form carbonic acid in the presence of the enzyme carbonic anhydrase. Carbonic anhydrase is a zinc enzyme that speeds up the formation of carbonic acid. This carbonic acid dissociates into bicarbonate (HCO3 –) and hydrogen ions (H+ ).
Q5: What will be the pO2 and pCO2 in the atmospheric air compared to those in the alveolar air?
(i) pO2 lesser, pCO2 higher
(ii) pO2 higher, pCO2 lesser
(iii) pO2 higher, pCO2 higher
(iv) pO2 lesser, pCO2 lesser
Ans 5: (ii) pO2 higher, pCO2 lesser
The partial pressure of oxygen in atmospheric air is higher than that of oxygen in alveolar air. In atmospheric air, pO2 is about 159 mm Hg. In alveolar air, it is about 104 mm Hg. The partial pressure of carbon dioxide in atmospheric air is lesser than that of carbon dioxide in alveolar air. In atmospheric air, pCO2 is about 0.3 mmHg. In alveolar air, it is about 40 mm Hg.
Q6: Explain the process of inspiration under normal conditions.
Ans:
Q7: How is respiration regulated?
Ans:
Q8: What is the effect of pCO2 on oxygen transport?
Ans: pCO2 plays an important role in the transportation of oxygen. At the alveolus, the low pCO2 and high pO2 favours the formation of haemoglobin. At the tissues, the high pCO2 and low pO2 favours the dissociation of oxygen from oxyhaemoglobin. Hence, the affinity of haemoglobin for oxygen is enhanced by the decrease of pCO2 in blood. Therefore, oxygen is transported in blood as oxyhaemoglobin and oxygen dissociates from it at the tissues.
Q9: What happens to the respiratory process in a man going up a hill?
Ans: As altitude increases, the oxygen level in the atmosphere decreases. Therefore, as a man goes uphill, he gets less oxygen with each breath. This causes the amount of oxygen in the blood to decline. The respiratory rate increases in response to the decrease in the oxygen content of blood. Simultaneously, the rate of heart beat increases to increase the supply of oxygen to blood.
Q10: What is the site of gaseous exchange in an insect?
Ans: In insects, gaseous exchange occurs through a network of tubes collectively known as the tracheal system. The small openings on the sides of an insect’s body are known as spiracles. Oxygen-rich air enters through the spiracles. The spiracles are connected to the network of tubes. From the spiracles, oxygen enters the tracheae. From here, oxygen diffuses into the cells of the body.
The movement of carbon dioxide follows the reverse path. The CO2 from the cells of the body first enters the tracheae and then leaves the body through the spiracles.
Q11: Define oxygen dissociation curve. Can you suggest any reason for its sigmoidal pattern?
Ans:
Q12: Have you heard about hypoxia? Try to gather information about it, and discuss with your friends.
Ans: Hypoxia is a condition characterised by an inadequate or decreased supply of oxygen to the lungs. It is caused by several extrinsic factors such as reduction in pO2, inadequate oxygen, etc. The different types of hypoxia are discussed below.
Hypoxemic hypoxia
Anaemic hypoxia
Histotoxic hypoxia
Q13: Distinguish between
(a) IRV and ERV
(b) Inspiratory capacity and Expiratory capacity
(c) Vital capacity and Total lung capacity
Ans: (a) IRV and ERV
(b) Inspiratory capacity and Expiratory capacity
(c) Vital capacity and Total lung capacity
Q14: What is Tidal volume? Find out the Tidal volume (approximate value) for a healthy human in an hour.
Ans: Tidal volume is the volume of air inspired or expired during normal respiration. It is about 6000 to 8000 mL of air per minute. The hourly tidal volume for a healthy human can be calculated as:
Tidal volume = 6000 to 8000 mL/minute
Tidal volume in an hour = 6000 to 8000 mL × (60 min) = 3.6 × 105 mL to 4.8 × 105 mL
Therefore, the hourly tidal volume for a healthy human is approximately 3.6 × 105 mL to 4.8 × 105 mL.
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1. What is the process of breathing? |
2. How does the exchange of gases occur in the lungs? |
3. What are the main respiratory organs involved in breathing? |
4. How does the respiratory system help in maintaining the body's pH balance? |
5. What are some common respiratory disorders that affect breathing? |
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