Which extracellular cation is most abundant in body fluids?

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Multiple Choice

Which extracellular cation is most abundant in body fluids?

Sodium is the most abundant cation in the extracellular fluid, and it largely sets the osmolarity and volume of that compartment. The body keeps a high level of sodium outside cells, mainly through the Na+/K+-ATPase pump, which shuttles Na+ out of cells and K+ in. This gradient maintains the resting membrane potential and supports fluid balance, nerve impulses, and muscle function. Potassium is primarily intracellular, so its extracellular concentration is comparatively low, while calcium and magnesium are present extracellularly but at much lower concentrations than sodium.

Sodium is the most abundant cation in the extracellular fluid, and it largely sets the osmolarity and volume of that compartment. The body keeps a high level of sodium outside cells, mainly through the Na+/K+-ATPase pump, which shuttles Na+ out of cells and K+ in. This gradient maintains the resting membrane potential and supports fluid balance, nerve impulses, and muscle function. Potassium is primarily intracellular, so its extracellular concentration is comparatively low, while calcium and magnesium are present extracellularly but at much lower concentrations than sodium.

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