Chapter 17 Breathing and Exchange of Gases Solutions
Question - 11 : - Define oxygen dissociation curve. Can you suggest any reason for its sigmoidal pattern?
Answer - 11 : -
1. Oxygen dissociationcurve: It is graphic respresentation of relationship between partial pressureof oxygen or p02 and percentage saturation of haemoglobin withoxygen.
2. The graph is sigmoidas at low p02, there is reduced synthesis of oxyhaemoglobin.Percentage of oxyhaemoglobin rises with higher p02 till atabout p02 is 100mm Hg, the haemoglobin becomes fully saturatedwith 02.
3. Further rise in p02 cannotincrease the value of oxyhaem-oglobin as the blood is already saturated withit.
Question - 12 : - Have you heard about hypoxia ? Try to gather information about it, and discuss with your friends.
Answer - 12 : -
Hypoxia refers to shortage of oxygen supply to the body. It is of different types:
1. Anaemic hypoxia (deficiency of haemoglobin),
2. Cytotoxic hypoxia (impaired utilization as in cyanide poisoning)
3. Stagnant hypoxia. Due to heart failure or reduced pumping activity of heart.
4. Hypoxic hypoxia. Insufficient oxygen in air as at high altitude.
5. CO Poisoning. Carbon monoxide binds to haemoglobin irreversibly. Oxygen transport is correspondingly reduced.
Question - 13 : - Distinguish between
(a) IRV and ERV
(b) Inspiratory capacity and Expiratory capacity.
(c) Vital capacity and Total lung capacity.
Answer - 13 : -
(a) IRV and ERV
| IRV (Inspiratory reserve volume) | ERV (Expiratory reserve volume) |
| It is the volume of air that a person can additionally inspire through a compelled inspiration | It is the volume of air that a person can expire through an expelled expiration |
| For a healthy individual, the IRV is approximately 2500ml – 3000ml | For a healthy individual, the ERV is approximately 1000ml to 1100ml |
(b) Inspiratorycapacity and Expiratory capacity
| Inspiratory capacity (IC) | Expiratory capacity (EC) |
| Inspiratory capacity is the volume of air that can be inhaled post a normal expiration | Expiratory capacity is the volume of air that can be exhaled post a normal inspiration |
| It is given by the sum of tidal volume and the inspiratory reserve volume i.e, IC = TV + IRV | It is given by the tidal volume and the expiratory reserve volume i.e., EC = TV + ERV |
(c) Vital capacity andTotal lung capacity
| Vital capacity (VC) | Total lung capacity (TLC) |
| After a maximum inspiration, it is the maximum volume of air that can be exhaled. It includes IC and ERV. | After maximum inspiration, it is the volume of air in the lungs. It includes ERV, IC and residual volume |
| The vital capacity in the lungs of humans is about 4000ml | The total lung capacity in the lungs of humans is nearly 5000ml to 6000ml |
Question - 14 : - What is tidal volume ? Find out the tidal volume (approximate value) for a healthy human in an hour.
Answer - 14 : -
Volume of air inspired/breath during normal respiration. It is approximate 500mL.Number of breaths per minute 12 to 16.
Tidal volume per minute = 500 x 12 to 16 = 6000 – 8000 mL or 6 -8 litres Tidal volume per hour = 6 to 8 x 60 = 360 – 480 litres.