What is potassium’s role in fluid balance and cardiovascular health?

• A. It regulates vitamins
• B. It is the major intracellular cation; maintains fluid/electrolyte balance, supports nerve and muscle function, and helps regulate blood pressure
• C. It provides stored energy
• D. It is the major extracellular cation; only affects bone

Answer: (B)

Potassium’s role in fluid balance and cardiovascular health comes from its status as the major intracellular cation. Most of the body’s potassium is inside cells, which helps maintain osmotic balance and fluid distribution between compartments. This inside-the-cell pool also drives nerve signaling and muscle contraction, including the heart, by maintaining the proper resting membrane potential and enabling repolarization after electrical impulses. In terms of blood pressure, potassium promotes the excretion of sodium by the kidneys and can relax vascular smooth muscle, supporting lower blood pressure and reduced cardiovascular risk. Because balance is essential, both too little and too much potassium can disrupt heart rhythm and muscle function. Potassium is not a vitamin, not a stored energy source, and it’s not the major extracellular cation (that role belongs to sodium), nor does it merely affect bone.