Question

Temporary cessation of breathing after forced deep breathing for a few minutes, by a person sitting at rest is due to
A. Too much oxygen in the blood
B. Too much carbon dioxide in the blood
C. Very little carbon dioxide in the blood
D. Both, too much oxygen and very little carbon dioxide in the blood

Answer 1

Hint: The rate of respiration or breathing is controlled by the amount of carbon dioxide in the blood. The acidity of the blood is to be maintained at an accurate level. Partial pressures will cause the diffusion of gases.

Complete answer:
Breathing is the process of the exchange of gases in the lungs, mostly by bringing in oxygen and flushing out carbon dioxide. Repetitive cycles of inhalation and exhalation lead from nose to the alveoli.

There is a difference in the composition of air in the atmosphere and alveoli. Alveoli have a greater amount of carbon dioxide and lesser amount of oxygen than the atmosphere. Due to this compositional change, there is diffusion of gases or the entry and flushing of gases. Forced and relaxed breathing can alter this composition.

Deep breathing will cause an increase in the oxygen level of blood. The acidity of blood increases due to the excess formation of oxyhaemoglobin.

Now, to maintain the pH, more free carbon dioxide will change to bicarbonates. Thus, the carbon dioxide level in the blood will decrease.

So, the answer is option D – Both, too much oxygen and very little carbon dioxide in the blood.

Note: Alveoli air has a greater amount of carbon dioxide and less oxygen than atmospheric air. Deep or forced breathing causes alveolar air composition to be changed. As a result, the partial pressure of oxygen and carbon dioxide changes causing the diffusion of gases across the membrane. This causes oxygen to enter and carbon dioxide to leave the blood more quickly.