The Digestive, Respiratory, and Urinary Systems
Which of the following parameters does the brain monitor most closely in regulating the rate of respiration?
|A||The concentration of oxygen in the blood.|
|C||The concentration of carbon dioxide in the blood and the blood pH.|
|D||The concentration of lactic acid in the blood.|
Since the carbon dioxide concentration is so closely linked with the pH of the blood, the brain uses these parameters to gather information about the actions to take to control the respiratory rate. While the concentration of oxygen could be monitored logically (and is, by the carotid and aortic bodies), this is a fine tuning measure, and is not a major source of regulation (choice A). Choice B is incorrect, because the heartrate is regulated by similar mechanisms as the respiration rate; one does not directly affect the other. Choice D is unsupported by the passage, and untrue.