Question

When $CO_2$ concentration in blood increases, breathing becomes

A) Shallower and slow

B) There is no effect on breathing

C) Slow and deep

D) Faster and deeper

Answer 1

Hint: Blood serves to transport respiratory gases. Breathing pattern gets altered when the concentration of gases in the blood increases or decreases.

Complete answer:

Oxygen combines with hemoglobin in the blood and is transported as oxyhemoglobin. Transport of oxygen in this form is important because the maximum amount (97%) of oxygen is transported by this method. When $CO_2$ concentration in the blood increases the affinity of $CO_2$ for binding with hemoglobin increases (Bohr effect). Bohr effect is the effect by which the presence of $CO_2$ decreases the affinity of hemoglobin for $O_2$. Excess of carbon dioxide stimulates the respiratory centers causing hyperventilation. 

Hyperventilation means increased pulmonary ventilation. In hyperventilation, both rate and force of breathing are increased, that is breathing becomes faster and deeper. During hyperventilation, excessive carbon dioxide is washed out and the body restores the normal breathing rhythm.

Hence, the correct answer is option (D).

Note: Some important terms:-

i) Hypercapnia is the increased carbon dioxide content of the blood.

ii) Hypocapnia is the decreased carbon dioxide content in the blood.

iii) Tachypnea: Increase in the rate of respiration.

iv) Bradypnea: Decrease in the rate of respiration.

v) Apnea: Temporary arrest of breathing.

vi) Dyspnea: Difficulty in breathing.