What is primarily responsible for controlling respiration rate?

The primary control of respiration rate is largely managed by chemoreceptors, particularly those that are sensitive to carbon dioxide (CO2) levels in the cerebrospinal fluid (CSF). When CO2 levels rise in the blood, it is detected by these chemoreceptors, which respond by signaling the body to increase the respiratory rate. This increase in respiration helps to expel excess CO2 and restore normal levels.

While oxygen levels in the blood and physical activity levels can influence breathing patterns - with low oxygen potentially stimulating increased breathing and physical activity requiring more oxygen and thus increasing the rate as well - it is the CO2 levels that have a more immediate and strong regulatory effect through the central chemoreceptors. Nervous impulses from the spinal cord do play a role in the mechanics of breathing, but the primary chemical control of the rate is through the body's response to CO2 levels. Therefore, the sensitivity of chemoreceptors to CO2 in the cerebrospinal fluid stands out as the primary factor regulating respiration rate.