Question

1. If there is an increase in the PCO2 in the blood? What happens to respiration and in the kidneys?

2. When we hyperventilate what happens to the blood pH and why? What will the kidneys do?

3. If blood pressure goes up, what might happen in the kidney and what might be found in urine? Why is this?

Answer 1

1. Increase in the blood PCO2 causes increase in the hydrogen ions in the blood resulting in acidemia. The process of increased hydrogen ions in the blood is known as acidosis. As the acidosis is due to increase in the PCO2 and the subsequent increase in hydrogen ions it is a condition of respiratory acidosis.

CO2 + H2O --> H2CO3 --> H+ + HCO3-

This is a reversible reaction. Thus, with increase in carbon dioxide in the blood, pH of the blood falls due to increased hydrogen ions resulting in acidosis.

The body tries to compensate respiratory acidosis by creating metabolic alkalosis. Thus, the compensation for respiratory acidosis is retention of more bicarbonate ions from the kidneys as well as the respiratory rate is increased to exhale out more carbon dioxide from the body which helps in decreasing the level of carbon dioxide and hydrogen ions in the blood.

2. When we hyperventilate, more carbon dioxide is expelled out from the lungs thereby reducing the level of carbon dioxide in the blood. Carbon dioxide is converted to carbonic acid which is broken down into hydrogen ions thus the level of hydrogen ions corresponds with the level of carbon dioxide in the body. The reduced carbon dioxide level due to hyperventilation causes reduced level of hydrogen ions. Reduced hydrogen ions mean acidity is reduced and alkalinity is increased thus increasing the pH resulting in respiratory alkalosis. The body compensates respiratory alkalosis by creating metabolic acidosis through kidneys by excreting bicarbonate ions out of the body in urine.

3. In hypertensive patients, due to chronically raised blood pressure there is hyaline deposition in the renal blood vessels causing stiffening and hardening of renal arteries and arterioles. This hardening of renal blood vessels (arteriosclerosis) causes impaired blood flow to the nephrons in the kidney resulting in damage to the glomerulus, bowman's capsule as well as to the renal tubules. This damage to the filtration barrier (glomerulus and bowman's capsule) causes impaired filtration of blood cells and proteins like albumin which are normally filtered out and send back to the circulation. Thus, there is inadequate filtration of red blood cells and large proteins like albumin in patients of chronically raised blood pressure. Hence, the urine in these patients show red blood cells (hematuria) and proteins like albumin (proteinuria).