Question

A person sitting at rest experiences a temporary cessation of breathing after forced deep breathing for a few minutes. This is due to

A) Too much $CO_2$ in blood

B) Too much $O_2$ in blood

C) Very little $CO_2$ in blood

D) Both high $O_2$ and very little $CO_2$ in blood

Answer 1

Hint: To promote gas exchange with the internal environment, breathing (or ventilation) is the method of moving air into and out of the lungs, often by taking in oxygen and flushing out carbon dioxide.

Complete answer:

Breathing consists of repeated inhalation and exhalation processes through the airways leading to the alveoli from the nose.The alveoli are the "forest" blind-ended terminals, meaning that any air that reaches them must exit the alveoli through the same path it used to reach them. 

Such a device produces dead space, an amount of air that at the end of inhalation fills the airways (dead space), and is breathed out, unchanged, without ever touching the alveoli during the next exhalation.

The air quality is different in the atmosphere and in the alveoli.The exchange of gases is a passive process. Diffusion holds it in place. Gases migrate from a high partial pressure to a low partial pressure during diffusion.  A higher volume of carbon dioxide and less oxygen than ambient air is found in alveolar air. This is because transferring gas extracts oxygen from the alveolar air and adds carbon dioxide. 

Deep and forced breathing both cause the composition of alveolar air to change more quickly than during quiet breathing.The partial pressures of oxygen and carbon dioxide change as a result of this, affecting the mechanism of diffusion that passes gases through the membrane.

 This will allow oxygen to enter the blood and carbon dioxide to exit the blood quicker, because of which , the blood will have high levels of oxygen and very little carbon dioxide.

Similarly, at the end of exhalation, the dead space is filled with alveolar air and is the first air to breathe back into the alveoli until any fresh air during inhalation enters the alveoli.

The correct Answer is option (D), Both high $O_2$ and very little $CO_2$ in blood.

Note: Inhaled air is 79% nitrogen, 20.95% oxygen and small quantities of other gases, including argon , carbon dioxide, neon, helium, and hydrogen, by volume. In terms of carbon dioxide volume, the gas exhaled is 4 percent to 5 percent, around a 100-fold improvement over the inhaled level. Compared to the oxygen inhaled, the oxygen content is decreased by a slight amount, 4 percent to 5 percent.