Question

breathing rate and tidal volume increase when ____ levels in the body ____.
o oxygen; decrease
o carbon dioxide; decrease
o hydrogen ion; decrease
o carbon dioxide; increase

Explanation:

When carbon dioxide levels increase in the body, it leads to an increase in hydrogen ions (due to the reaction \(CO_2 + H_2O
ightarrow H_2CO_3
ightarrow H^+ + HCO_3^-\)). The chemoreceptors detect this change. The body's response to maintain homeostasis is to increase the breathing rate and tidal volume. This helps to expel more carbon dioxide (as \(CO_2\) is removed during exhalation), thus reducing the hydrogen ion concentration and bringing the body back to a more normal physiological state. If oxygen levels decrease, the primary response is also related to breathing regulation, but the direct chemical - stimulus related to the immediate increase in breathing rate and tidal volume in the context of a gas is more directly tied to \(CO_2\) increase. When \(CO_2\) decreases or hydrogen ion decreases, there is no stimulus for an increase in breathing rate and tidal volume.

Answer:

carbon dioxide; increase