Overview
This lecture explains why volume contraction results in metabolic alkalosis, focusing on the effects of aldosterone on kidney function.
Volume Contraction and Hormonal Response
- Volume contraction refers to reduced body fluid volume.
- This condition stimulates increased renin release.
- Renin increases aldosterone secretion from the adrenal glands.
Aldosterone Effects Leading to Metabolic Alkalosis
- Aldosterone enhances the activity of the sodium-potassium pump in the nephron.
- This results in increased sodium reabsorption and potassium excretion in the urine.
- Increased potassium excretion leads to hypokalemia (low blood potassium).
- In hypokalemia, intracellular potassium decreases, causing hydrogen ions to move into the cell.
- Reduced extracellular hydrogen concentration contributes to metabolic alkalosis.
Aldosterone and Hydrogen Secretion
- Aldosterone also stimulates the hydrogen ATPase in the collecting duct.
- This increases hydrogen ion secretion into the urine.
- Less hydrogen in the extracellular fluid further leads to metabolic alkalosis.
Key Terms & Definitions
- Volume Contraction — a decrease in the volume of body fluids.
- Renin — an enzyme that increases aldosterone production.
- Aldosterone — a hormone that increases sodium reabsorption and potassium/hydrogen secretion in the nephron.
- Nephron — the functional unit of the kidney.
- Metabolic Alkalosis — a condition where blood pH increases due to low hydrogen ion concentration.
- Hypokalemia — abnormally low potassium levels in the blood.
Action Items / Next Steps
- Review kidney regulation of acid-base balance, focusing on aldosterone's role.
- Understand related disorders such as metabolic alkalosis and hypokalemia.