What respiratory response is stimulated by a small increase in CO2 concentration?

• A. Hypopnea
• B. Hyperpnea
• C. Tachypnea
• D. Apnea

Answer: (B)

A small increase in carbon dioxide (CO2) concentration in the blood leads to hyperpnea, which refers to an increase in the depth and rate of breathing. This response is primarily mediated by the chemoreceptors in the body that detect changes in blood gases. When CO2 levels rise, it results in a decrease in blood pH (more acidic), stimulating the respiratory centers in the brain to enhance ventilation to eliminate the excess CO2 and restore pH balance.

Hyperpnea occurs as the body attempts to increase the oxygen intake and carbon dioxide removal to compensate for the increased CO2 levels. This response is essential for maintaining homeostasis and ensuring that sufficient oxygen is delivered to the tissues while excess CO2 is removed efficiently.

In contrast, options like hypopnea indicate a decrease in the rate and/or depth of breathing, tachypnea denotes an increased respiratory rate often without an increase in depth, and apnea refers to a temporary cessation of breathing. These responses do not align with how the body reacts to a small increase in CO2 concentration.