RESPIRATION ::
The respiratory system also plays an important role in maintaining pH of the blood An increase in CO2 concentration in body fluids can lower the pH as follows :
CO2+H2O --------> H2CO3 ----------> H++HCO3-
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Conversely a decrease in CO2 Concentration in body fluids can raise the pH Thus the pH of body fluids may be adjusted by a change in the rate of breathing Increase in the rate of breathing will exhale out CO2 Resulting in rise in pH and slowing down of breathing will tend to decrease the pH In fact the respiratory centres in medulla oblongata of the brain are stimulated when pH of the blood falls
KIDNEY :::
Next to respiratory system kidneys play the most important role in maintaining pH The mechanisms involved in kidney are excretion of H+ ions and reabsorption of HCO3 - Besides this formation of ammonia is another important mechanism that helps in acid-base balance
The epithelial cells of all the tubules besides those of the thin segment of the loop of henle can synthesize ammonia Ammonia (NH3) then reacts with H+ to form ammonium ion (NH4+) This is then excreted into the urine in combination with chloride ion (as NH4CI) The net effect is thus to increase sodium bicarbonate concentration in the extracellular fluid Thus increase in H+ ion concentration causes formation of more ammonia to regulate acid -base balance
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