When the body detects that there are high levels of protons in blood (causing blood to be excessively acidic), it reacts through multiple organ systems to restore blood back to its neutral or slightly alkaline state.
The medulla has chemoreceptors which measure the pH of the blood. They respond to decreased blood pH by increasing the ventilation rate of the lungs through nervous system innervation of the diaphragm and external intercostal muscles. This increased exhalation of CO2 will cause a compensatory increase in pH.
By increasing the ventilation rate, the medulla forces the expulsion of carbon dioxide through the lungs. This shifts the buffer system away from producing protons, due to LeChatlier's principle. Thus, as CO2 levels decrease, pH increases.
Another method of increasing blood pH is by increasing the bicarbonate reabsorption from the kidney. As bicarbonate levels in the blood increase, the blood pH increases as well.
The kidney can excrete excess hydrogen ions into the urine, which can directly increase the blood's pH.
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