Chemicals in the blood modulate rate and depth of breathing to control CO2 and..

Increasing H+ levels stimulate central chemoreceptors.
                                       

Thank you bio_man!

You're welcome! Any luck on the 2nd question?

unfortunately, no luck on that question. I have been searching all day though.

The normal pH of arterial blood is 7.4. A person is considered to have acidosis when the pH is below this value and to have alkalosis when it rises above pH 7.4. The lower limit at which a person can live is about pH 7.0 and the upper limit is about pH 7.8. To prevent a change in the pH of the body, all body fluids including cytoplasm are buffered. A buffer is a chemical or a combination of chemicals that can absorb either hydrogen ions (H+) or hydroxide ions and therefore maintain a relatively constant hydrogen ion concentration.
Proteins are effective chemical buffers both within cells and within blood. Hemoglobin is the most active protein buffer within blood, and it absorbs excess hydrogen ions when it is not carrying oxygen.

There are two other types of chemical buffers in body fluids--the carbonate and phosphate buffer systems. The phosphate system (NaH2PO4 and Na2HPO4) effectively buffers urine and cytoplasm. The carbonate system (a mixture of carbonic acid, H2CO3, and sodium bicarbonate, NaHCO3) is present in both tissue fluid and blood. The concentration of buffering substances is regulated by the lungs and/or kidneys. For example, when carbon dioxide is exhaled by the lungs or the bicarbonate ion is excreted by the kidneys, the concentration of the buffering substances can return to their most effective levels.

If the hydrogen ion concentration of the blood remains high, the respiratory center of the medulla oblongata is stimulated and the breathing rate increases. As carbon dioxide is excreted the pH shifts toward normal. This respiratory regulation of the acid-base balance is a physiological type of buffer system that is an important adjunct to the chemical systems discussed.

The kidneys are a powerful mechanism by which the pH may be regulated. The kidneys may form either an acid or alkaline urine, bringing the hydrogen ion concentration back toward normal. When the kidneys form an acid urine, they excrete H+, and when the kidneys form an alkaline urine, they excrete the bicarbonate ion. However, the full effect of the kidneys is not realized for ten to twenty hours.

Notice that the pH of the body is regulated in three ways. Chemical buffers both within cells and within body fluids react immediately to regulate the hydrogen ion and hydroxide ion concentrations. The pulmonary system requires a few minutes to bring about its effects while the kidneys take from ten to twenty hours. The kidneys, however, are the most powerful of the three.