Chapter 17 Breathing and Exchange of Gases Solutions
Question - 1 : - Define vital capacity. What is its significance ?
Answer - 1 : -
The maximum volume of air a person can breathe in after a forced expiration. This includes ERV, TV and IRV or the maximum volume of air a person can breathe out after a forced inspiration.
It represent the maximum amount of air one can renew in the respiratory system in a single respiration. Thus, greater the vital capacity more is the energy available to the body for doing strenous work. Vital capacity is higher in athletes and mountain dwellers. Young persons would possess more vital capacity as compared to children or older persons.
Question - 2 : - State the volume of air remaining in the lungs after a normal breathing.
Answer - 2 : -
Volume of air remaining in lungs after a normal respiration is called functional residual capacity. It includes ERV + RV = Expiratory reserve volume + residual volume
Question - 3 : - volume Diffusion of gases occurs in the alveolar region only and not in the other parts of respiratory system. Why ?
Answer - 3 : -
Alveoli are the primary sites of exchange of gases. Alveolar region is having enough pressure gradient to facilitate diffusion of gases. Other regions of the respiratory sytsem don’t have the required pressure gradient. Additionally the membrane of alveoli is thin enough to facilitate exchange of gases in a convenient manner.
Question - 4 : - What are the major transport mechanisms for C02 ? Explain.
Answer - 4 : -
Transport of carbon dioxide : About 4 ml of carbon dioxide is transported by every 100 ml of blood.
C02 is transported in three forms in the blood.
(i) In the dissolved form in plasma about 7% of C02 dissolves in plasma of blood, just as it gets dissolved in water.
(ii) As bicarbonates
• Erythrocytes have a high concentration of the enzyme, carbonic anhydrase which catalyses the following reactions;
About 70% of C02 is transported as bicarbonates.
(iii) As carbaminohaemoglobin
• C02 combines with of the globin part of haemoglobin and forms carbamino haemoglobin. About 23% of C02 transported in this manner.
Question - 5 : - What will be the pO2 and pCO2 in the atmospheric air compared to those in thealveolar air ?
(i) pO2 lesser,pCO2higher
(ii) pO2 higher,pCO2lesser
(iii) pO2 higher,pCO2 higher
(iv) pO2 lesser,pCO2lesser
Answer - 5 : -
(ii) pO2 higher, pCO2 lesser
pO2 higher willcreate the pressure gradient to facilitate the movement of O2 from atmosphere toalveoli and pCO2 lesserwill create the movement of CO2 fromalveoli to atmosphere.
Question - 6 : - Explain the process of inspiration under normal conditions.
Answer - 6 : -
- Inspiration occurs when pressure within lungs is less than the atmospheric pressure, i.e., there is a negative pressure in the lungs with respect to atmospheric pressure.
- Inspiration is initiated by the contraction of diaphram which increases the volume of thoracic chamber in the antero-posterior axis.
- The contraction of external inter-costal muscles lifts up the ribs and the sternum causing an increase in the volume of a thoracic chamber in the dorso- ventral axis.
- The overall increase in thoracic volume causes a similar increase in pulmonary volume.
- An increase in pulmonary volume decreases the intra pulmonary pressure, to less than atmospheric pressure which forces the air from outside to move into the lungs i.e., inspiration.
Question - 7 : - How is respiration regulated ?
Answer - 7 : -
1. Respiratory rhythmcentre, present in medulla region of brain is responsible for respirationregulation.
2. Its function can bemoderate by pneumotaxic centre, present in pons region of brain.
3. A chemosensitive areapresent adjacent to rhythm centre, is highly sensitive to C02 andH+.
4. Chemosenstive centredue to increase in C02 and H+ can signal therhythm centre to make adjustment to eliminate these substances.
5. Receptors associatedwith aortic arch and carotid artery also can recognise changes in CO2 andH+ concentration and send necessary signals to rhythm centrefor remedial actions.
Question - 8 : - What is the effect of pC02 on oxygen transport?
Answer - 8 : -
At low pC02,blood can carry the maximum amount of oxygen as oxyhaemoglobin. At high pCO2, the affinity for oxygendecreases and oxyhaemoglobin dissociates to free oxygen.
So at high pC02, oxygentransport is inhibited.
Question - 9 : - What happens to the respiratory process in a man going up a hill ?
Answer - 9 : -
When a man is going uphill or doing some strenuous exercise then there is more consumption of oxygen. This decreases the partial pressure of oxygen in haemoglobin resulting in more demand of haemoglobin. As a result there is an increased breathing rate to fill the gap.
Question - 10 : - What is the site of gaseous exchange in an insect ?
Answer - 10 : -
Insect have a complex system of intercommunicating air tubes called tracheae to enable them to exchange gases between the environment and the body cells (tracheal respiration).