Final answer:
Sodium is the major cation in the extracellular fluid and is excreted in urine. Excessive sodium intake can contribute to high blood pressure. Sodium is important for osmotic pressure balance.
Step-by-step explanation:
Sodium is the major cation in the extracellular fluid and is responsible for osmotic pressure gradient. In a typical Western diet, people consume excess sodium, which can lead to hypertension. The kidneys primarily excrete sodium through urine.