Final answer:
The kidneys are the major organ that balances sodium and potassium in the body, regulating their levels to maintain homeostasis and normal osmotic pressure.
Step-by-step explanation:
The major organ that balances sodium and potassium in the body is the kidneys. These vital organs are involved in various homeostatic functions, including the regulation of electrolyte concentrations. Sodium and potassium are essential electrolytes that maintain normal osmotic pressure and protect the body against excessive fluid loss.
The kidneys regulate the levels of these ions in the blood through processes such as filtration, reabsorption, and secretion. In particular, potassium is the major intracellular cation that is crucial for establishing the resting membrane potential in neurons and muscle fibers, while sodium is key for osmotic pressure maintenance.
The balance of sodium and potassium is also regulated by the hormone aldosterone, which promotes the exchange of these electrolytes in the renal tubules.