Breathing and Exchange of Gases

| 257

In alveoli, pCO2 is low, the above reaction proceeds in opposite direction

leading to the formation of CO2 and H2O. Every 100 ml of deoxygenated blood

delivers about 4ml of CO2 to the alveoli.

RËGÜLÅTÏØÑ ØF RËSPÏRÅTÏØÑ



In humans, respiration is under the control of both nervous and chemical

regulation.



Respiratory centres present in the brain.



Respiratory rhythm centre (Inspiratory and Expiratory centres) : In

medulla oblongata.



Pneumotaxic centre : In Pons. It moderates functions of respiratory

rhythm centre. Impulse from this centre reduces the duration of

inspiration and thereby alter respiratory rate.



Another centre present in the pons region of brain is called pneumotaxic

centre.



Chemosensitive area : Seen adjacent to the rhythm centre.

Increase in the concentration of CO2 and H⁺ activates this centre, which in

turn signals rhythm centre. Receptors in aortic arch & carotid artery also

recognize changes in CO2 & H⁺ concentration and send signals to rhythm

centre. Role of oxygen in the regulation of respiratory rhythm is quite

insignificant.

DÏSØRDËRS ØF RËSPÏRÅTØRÝ SÝSTËM

ÅSTHMÅ

Difficulty in breathing causing wheezing due to inflammation of bronchi and

bronchioles.

ËMPHÝSËMÅ (Chronic Disorder)

Damage of alveolar walls. It decreases respiratory surface. Major cause is

cigarette smoking.

[AIPMT 2015]

ØÇÇÜPÅTÏØÑÅL RËSPÏRÅTØRÝ DÏSØRDËRS

Certain industries (involving grinding or stone breaking) produce so much dust. So,

the defense mechanism of the body cannot cope with the situation. Long exposure

causes inflammation leading to fibrosis (proliferation of fibrous tissues). It results in

lung damage. Workers in such industries should wear protective masks.