Blood ph and cerebrospinal fluid ph are affected by carbon dioxide content. how does this enable the organism to sense a disturbance in gas levels? question 2 options: a. the brain alters the ph of the cerebrospinal fluid to force the animal to retain more or less carbon dioxide b. the brain directly measures and monitors carbon dioxide and causes breathing changes accordingly c. the medulla oblongata is able to control the concentration of bicarbonate ions in the blood d. the medulla oblongata, which is in contact with cerebrospinal fluid, monitors ph and uses this measure to control breathing e. the lungs sense changes in oxygen concentration, which causes the medulla oblongata to speed up or slow breathing