Electrolyte and Water Balance
Start with the big picture
Sodium is the main extracellular cation and a key determinant of extracellular fluid volume and blood pressure. The kidneys reabsorb most filtered sodium, with final handling influenced by aldosterone in the collecting duct. Potassium is the principal intracellular cation, and changes in extracellular potassium can affect cardiac rhythm. Principal cells secrete potassium, while intercalated cells can reabsorb it; hormonal and physiological conditions influence this handling. Water balance is regulated in part by antidiuretic hormone (ADH), released in response to increased plasma osmolarity or decreased volume. ADH increases water reabsorption in the collecting duct by promoting insertion of aquaporin-2 channels. Together, these mechanisms show how the nephron and hormones coordinate electrolyte and water regulation.
What you'll learn
- Explain sodium’s role in extracellular fluid volume and blood pressure.
- Describe how aldosterone influences final sodium handling in the collecting duct.
- Identify the roles of principal and intercalated cells in renal potassium handling.
- Explain the triggers and collecting-duct action of ADH.
- Recognize how hormonal signals help fine-tune electrolyte and water balance.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
