Final answer:
Chemoreceptors in the medulla oblongata and the aorta and carotid arteries detect changes in blood levels of oxygen, carbon dioxide, and hydrogen ions (pH), triggering responses to maintain vascular homeostasis. They stimulate respiratory and cardiovascular adjustments via the glossopharyngeal and vagus nerves when these levels significantly deviate from the norm.
Step-by-step explanation:
The chemoreceptors located in the medulla oblongata, aorta, and carotid arteries are specialized sensors that play a critical role in maintaining vascular homeostasis. These chemoreceptors are responsible for detecting changes in the levels of oxygen (O2), carbon dioxide (CO2), and hydrogen ions (pH) in the blood. In addition, these receptors sense specific metabolic byproducts such as lactic acid which accrue during increased physical activity.
When there is a significant reduction in blood oxygen levels or an increase in the concentration of CO2 or hydrogen ions, these peripheral chemoreceptors stimulate changes in cardiovascular and respiratory functions. The decrease in blood oxygen to levels around or below 60 mm Hg prompts an increased respiratory rate to compensate for the reduced oxygenation. Notably, these chemoreceptors can only detect the dissolved portion of oxygen in the blood, not the oxygen that is bound to hemoglobin. The increase in respiratory activity helps to stabilize the levels of oxygen and carbon dioxide in the blood, thereby aiding in the maintenance of a stable internal environment (homeostasis).
The chemoreceptors are innervated by the glossopharyngeal and vagus nerves, providing feedback to the cardiovascular center about the body's need for adjusting blood flow and pressure in response to the detected levels of dissolved gases and metabolic byproducts.