Category: mineral
Aliases: Na⁺, Sodium chloride, Salt
Dominant extracellular cation (~140 mEq/L ECF vs ~10 mEq/L ICF). The Na⁺ gradient set by Na⁺/K⁺-ATPase establishes the resting membrane potential alongside K⁺ and powers secondary-active transport across virtually every epithelium (renal tubule, gut, BBB). Excess intake elevates BP via fluid retention; deficiency is rare but clinically significant in endurance athletes, diuretic therapy, and SIADH.