Final answer:
The two electrolytes that help control the water balance in the extracellular space are sodium and chloride. These are crucial for maintaining osmotic pressure and fluid balance, and are tightly regulated by hormones like aldosterone.
Step-by-step explanation:
The two electrolytes that help to control the water balance in the extracellular space are sodium and chloride. Sodium (Na+) plays a crucial role in the distribution and retention of body water, critically affecting osmotic pressure and fluid balance within the extracellular fluid (ECF). At the same time, chloride (Cl-) follows sodium to maintain the electrolyte balance, and together they are essential in osmotic control and acid-base balance. Aldosterone primarily affects the exchange of sodium and potassium; it promotes sodium reabsorption and potassium excretion in the kidneys. Athletes are often encouraged to replenish these electrolytes during extended periods of activity to maintain hydration and electrolyte balance.