Final answer:
Peripheral chemoreceptors in the aortic and carotid bodies respond to oxygen levels below 60 mm Hg by stimulating increased respiratory activity. These receptors sense dissolved oxygen and initiate physiological responses to maintain vascular homeostasis, coordinating the respiratory and cardiovascular systems.
Step-by-step explanation:
The chemoreceptors that are located in the aortic and carotid bodies and respond to an oxygen partial pressure below 60 mm Hg are known as peripheral chemoreceptors. These receptors are crucial in sensing large changes in blood oxygen levels and are only able to sense dissolved oxygen molecules, not the one that is bound to hemoglobin. As the majority of oxygen is carried by hemoglobin, it is only when dissolved levels of oxygen significantly drop that hemoglobin releases oxygen, thereby stimulating the chemoreceptors to activate an increase in respiratory activity. This mechanism is essential for maintaining vascular homeostasis and coordinating the respiratory and cardiovascular systems to meet the body's metabolic demands. The response of peripheral chemoreceptors to hypoxemia (oxygen levels dropping below 60 mm Hg) includes the stimulation of the respiratory centers in the medulla oblongata, thereby increasing the respiratory rate to draw more oxygen into the lungs and to expel carbon dioxide from the bloodstream. They also respond to changes in carbon dioxide and hydrogen ion levels (pH), contributing to the tight control of respiratory and cardiac activity.