A medication used to relax the airways in the lungs to increase air flow is:

A. Hemoglobin is an iron-containing protein found in red blood cells. It binds to oxygen in the lungs and carries it through the bloodstream to tissues throughout the body.
B. Antigens are substances that can trigger an immune response, but they are not involved in carrying oxygen in the blood.
C. Albumin is a protein in the blood that helps maintain osmotic pressure and transports various substances, but it does not carry oxygen.
D. Bicarbonate ions are involved in carbon dioxide transport in the blood, not oxygen. They help regulate the pH of blood and facilitate CO₂ transport from tissues to the lungs.

A. Carotid artery and aorta contain the carotid bodies and aortic bodies, which are peripheral chemoreceptors. These structures detect changes in blood oxygen, carbon dioxide, and pH levels, sending signals to the respiratory centers to adjust breathing accordingly.
B. The cerebellum and pons are parts of the brain involved in motor control and respiratory rhythm, respectively, but do not contain peripheral chemoreceptors.
C. The coronary sinus and alveoli are not involved in detecting chemical changes in the blood for breathing regulation. The coronary sinus drains blood from the heart muscle, and the alveoli are sites of gas exchange, not chemoreception.
D. The brachiocephalic vein and superior vena cava are large veins that return deoxygenated blood to the heart but do not house chemoreceptors involved in respiratory regulation.