Anatomy and Physiology II Practice Test

Which receptors modify respiratory rates based on carbon dioxide, oxygen, or acid levels in the blood?

1. Mechanoreceptors

2. Stretch receptors

3. Pain receptors

4. Chemoreceptors

The correct answer is: Chemoreceptors

Chemoreceptors play a crucial role in modulating respiratory rates in response to changes in the levels of carbon dioxide, oxygen, and hydrogen ions (which correlate with acidity) in the blood. These specialized sensory receptors are sensitive to the chemical composition of the blood and are primarily located in areas such as the carotid bodies and the medulla oblongata. When carbon dioxide levels rise (hypercapnia), the pH of the blood decreases (becomes more acidic), triggering chemoreceptors to stimulate an increase in the rate and depth of breathing. This enhances the expulsion of carbon dioxide from the body, thus helping to restore normal blood gas levels. Conversely, when oxygen levels drop (hypoxia), chemoreceptors also respond by signaling for increased respiratory activity to enhance oxygen intake. The other receptor types, such as mechanoreceptors, are primarily involved in sensing physical changes or mechanical stimuli, stretch receptors specifically monitor the degree of lung inflation, and pain receptors relate to nociception rather than directly influencing respiratory rates based on chemical changes.