Blood pH

• Similar to blood CO2
• Chemoreceptors detect changes in the levels of CO2, O2 and hydrogen ions (H+) in the blood
• They transmit this information to the respiratory centres in the brain stem (Medulla Oblongata and pons)
• Respiration affects blood pH by dictating the rate of removal of CO2 from the blood (hypoventilation or hyperventilation)
• Blood then enters the kidneys through the renal arteries and is filtered in the glomeruli
• This filtration process separates waste products and excess substances from the blood plasma
• The kidneys reabsorb bicarbonate ions from the filtrate back into the bloodstream
• The reabsorption helps to neutralise excess acids in the blood
• Hydrogen ions are secreted into the filtrate from the blood, removing excess acids from the bloodstream
• The kidneys adjust the rate of bicarbonate ions reabsorption and H+ secretion based on the bloods acid-base balance
• Acidosis (low pH) 

  • Respiratory Response - The brainstem (medulla) detects the low pH and increases the rate and depth of breathing. This increases the removal of CO2, this reducing the concentration of carbonic acid in the blood and increasing pH 
  • Renal Response - The kidneys increase the excretion of hydrogen ions and reabsorb more bicarbonate ions from the urine back into the blood. This helps to neutralise the excess acid and raise the blood pH
• Alkalosis (high pH) 

  • Respiratory Response - the brainstem detects the high pH and decreases the rate and depth of breathing. This retains the CO2 in the blood (which increase the concentration of carbonic acid), thus lowering the blood pH back to normal 
  • Renal Response - The kidneys reduce the reabsorption of bicarbonate ions and increase the excretion of bicarbonate in the urine. This helps to reduce the bloods nase level and lower the pH 6