Final answer:
The regulatory centers for the respiratory and circulatory systems are found in the medulla oblongata of the brain. These centers control the cardiovascular system and breathing muscles, and are stimulated by changes in blood chemistry and pH levels.
Step-by-step explanation:
The regulatory centers for the respiratory and circulatory systems are found in the medulla oblongata of the brain. The medulla contains nuclei referred to as the cardiovascular center, which controls the smooth and cardiac muscles of the cardiovascular system through autonomic connections. It also contains the respiratory centers that have control over breathing muscles. These centers are stimulated by factors such as chemical and pH changes in the blood, which results in an increase in respiratory rate and depth.