Final answer:
Breathing into a paper bag during hyperventilation helps restore blood carbon dioxide levels and stabilize blood pH, compensating for the excessive loss of CO₂ due to rapid breathing and preventing a rise in blood alkalinity.
Step-by-step explanation:
When an individual experiences hyperventilation, they exhale carbon dioxide (CO2) more quickly than it is produced. This leads to a decrease in blood CO2 levels, and consequently, the blood becomes more basic or alkaline, causing an increase in blood pH, a condition known as hypocapnia. If blood pH rises too much, it can lead to symptoms such as lightheadedness or even fainting. Breathing into a paper bag or cupped hands helps to prevent this increase in pH. By rebreathing exhaled air, which contains CO2, the individual can restore the blood's CO2 levels, and thus, stabilize blood pH towards normal levels.
The respiratory system regulates acids and bases in the body by controlling blood levels of carbonic acid. When hyperventilating, the person exhales CO2, which reduces the level of carbonic acid in the blood, making it too alkaline (alkalosis). The act of rebreathing helps to quickly bring blood pH down toward normal by reintroducing CO2 back into the body, balancing the acid-base equilibrium.
Therefore, although we can exert conscious control of breathing to some extent, our body's need to maintain a balanced pH level can override these attempts to avoid respiratory dysfunction and maintain homeostasis.