What is the principal extracellular cation?

• A. Sodium (Na+)
• B. Potassium (K+)
• C. Calcium (Ca2+)
• D. Magnesium (Mg2+)

Answer: (A)

Verified step by step guidance

1. Understand the concept of cations: Cations are positively charged ions. In the context of physiology, they play crucial roles in cellular functions and maintaining the body's electrolyte balance.
2. Identify the location: Extracellular refers to the space outside the cells. The principal extracellular cation is the one most abundant in the extracellular fluid.
3. Review the options: Sodium (Na+), Potassium (K+), Calcium (Ca2+), and Magnesium (Mg2+) are all cations, but they differ in their primary locations and functions within the body.
4. Consider the role of Sodium (Na+): Sodium is the most abundant cation in the extracellular fluid. It is essential for maintaining fluid balance, nerve function, and muscle contraction.
5. Conclude with the principal extracellular cation: Based on the abundance and role in the extracellular fluid, Sodium (Na+) is identified as the principal extracellular cation.