Final answer:
Potassium is the major cation found in intracellular fluid, while sodium is the major cation of the extracellular fluid. Chloride is the predominant extracellular anion.
Step-by-step explanation:
Potassium is the major cation found in intracellular fluid. It helps establish the resting membrane potential in neurons and muscle fibers after membrane depolarization and action potentials. Potassium levels are maintained by sodium-potassium pumps in cell membranes, which pump sodium out of the cell and potassium into the cell.
Sodium is the major cation of the extracellular fluid. It is responsible for one-half of the osmotic pressure gradient that exists between the interior of cells and their surrounding environment. Sodium is excreted primarily by the kidneys.
Chloride is the predominant extracellular anion. It plays an important role in maintaining proper hydration and balancing cations in the extracellular fluid. Chloride ions follow the paths of sodium ions in the renal system for secretion and reabsorption.