Biology for ( Grade 10 )

8.1 (a) Control of Respiration :

Respiration is controlled by the respiratory centre situated in medulla

oblongata of brain.

(i) Breathing occurs involuntarily.

(ii) Under normal conditions rate of breathing is 15-18 times per

minute. During vigorous exercise the demand for oxygen increases due

to which rate of breathing increases by about 20-25 times.

(iii) The total area for gas exchange covered through 300 million

alveoli is about 36-72 m^2 in each lung.

(iv) Respiratory quotient : It is defined as the ratio of the volumes of

CO 2 liberated and O 2 used during respiration.

8.1 (b) Some Respiratory Disorders :

• Emphysema : It occurs due to infection, smoking etc. It occurs due to
  obstructions in bronchioles caused by breaking of alveolar septa.
  Bronchodilators and O 2 therapy are used, for curing this disease.
  
  
  • Asthma : Air passages are narrowed and lead to obstruction in
  
  
  
  

breathing.

• Pneumonia : Lymph and mucous accumulate in alveoli and
  bronchioles. It occurs due to bacterial and viral infection.
  
  
  • Bronchitis : Swelling in living membranes of respiratory tract due to
  
  
  
  

excessive smoking.

• Tuberculosis : Bacterial infection in lungs.


• Pleurisy : Inflammation of lung membrane called as pleurisy.


• Sudden contraction of diaphragm along with loud closure of glottis

causes Hiccough.

• Sudden and violent expulsion of air through mouth and nose is called