What do chemo-receptors in the brain primarily monitor?

Chemo-receptors in the brain, particularly those located in the medulla oblongata, primarily monitor changes in the pH levels of the blood. This monitoring is crucial because blood pH is closely linked to the levels of carbon dioxide (CO2) in the blood; as CO2 levels increase, they lead to a decrease in pH (more acidic environment). These chemo-receptors respond to these changes by influencing respiratory rate and depth to help maintain homeostasis in the body.

By adjusting breathing, the body can regulate CO2 and, consequently, pH levels, ensuring that the internal environment remains stable. This mechanism highlights the importance of blood pH regulation in respiratory function and overall metabolic processes. The other options—temperature of the blood, arterial pressure, and oxygen levels—are regulated by different sensors and receptors, thus illustrating the specialized role of brain chemo-receptors in monitoring blood pH specifically.