Carbon Dioxide Levels in the Blood and in Cerebrospinal Fluid

Multiple Choice

Carbon dioxide levels in the blood and in cerebrospinal fluid affect the pH of these fluids. Which of the following mechanisms does an organism use to sense a disturbance in gas?

A) Neurons in contact with cerebrospinal fluid monitor pH and use this measure to control breathing.
B) Stretch receptors in the lungs cause the medulla oblongata to speed up or slow breathing.
C) The brain alters the pH of the cerebrospinal fluid to force the animal to retain more or less carbon dioxide.
D) The medulla oblongata is able to control the concentration of bicarbonate ions in the blood.
E) The brain directly measures and monitors oxygen levels and causes breathing changes accordingly.