électrolytes

Électrolytes are substances that dissociate into ions when dissolved in water (or melted), enabling an electric current to pass through the solution. In biology, the term usually refers to minerals and related ions present in body fluids that regulate fluid balance, nerve signaling, and muscle function.

Common electrolytes include sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), chloride (Cl−), bicarbonate (HCO3−), and phosphate (PO4^3−). Sodium and chloride help maintain extracellular fluid volume and osmolarity; potassium is the main intracellular cation important for action potentials; calcium and magnesium participate in muscle contraction, neurotransmission, and enzyme activity; bicarbonate and phosphate act as buffers to maintain pH.

Electrolytes arise from salts, acids, and bases. They can be classified as strong electrolytes, which fully dissociate in solution, or weak electrolytes, which only partly dissociate. Their balance is tightly regulated by the kidneys and by hormones such as aldosterone and antidiuretic hormone, and is influenced by diet and fluid intake.

Clinical relevance stems from electrolyte imbalances, which are assessed by measuring plasma ion concentrations and osmolality. Common disorders include hyponatremia and hypernatremia, hypokalemia and hyperkalemia, hypocalcemia and hypercalcemia, each with symptoms ranging from confusion and weakness to cardiac arrhythmias and seizures. Treatment typically involves adjusting fluid and electrolyte intake and, when needed, intravenous fluids such as normal saline or lactated Ringer’s solution. Proper electrolyte management is essential for hydration, blood pressure regulation, and acid–base balance.