What do central and peripheral chemoreceptors primarily sense in the body?

The correct choice identifies that central and peripheral chemoreceptors primarily sense carbon dioxide (CO2) levels and hydrogen ions in the body. These specialized receptors play a critical role in the regulation of respiratory function.

Central chemoreceptors, located in the brain, are highly sensitive to changes in the concentration of CO2 in the cerebrospinal fluid, which directly influences hydrogen ion concentration. An increase in CO2 leads to a decrease in pH (more acidic) due to the formation of carbonic acid, prompting a respiratory response to restore homeostasis.

Peripheral chemoreceptors, found in the carotid bodies and aortic arch, monitor both oxygen levels and CO2 levels in the blood. However, their most significant impact on respiratory drive occurs in response to increased CO2 and lowered pH, which signal the need for increased ventilation to expel excess CO2 and adjust the acid-base balance.

While oxygen levels are also important and are sensed by peripheral chemoreceptors, the primary regulatory mechanism for ventilation is largely influenced by CO2 levels and hydrogen ions. Blood pressure, heart rate, temperature, and pH are managed by other systems or receptors and are not the main focus of central and peripheral chemoreceptors in terms of regulating breathing.