Which one is the principal cation in the plasma of blood ?

Options

A. `K^(+)`
B. `Na^(+)`
C. `Ca^(2+)`
D. `Mg^(2+)`

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the principal cation found in the plasma of blood. Cations are positively charged ions.

2. **Identifying the Cations**: Common cations present in the blood plasma include sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), and magnesium (Mg²⁺).

3. **Determining the Principal Cation**: Among these cations, sodium is known to be the most abundant in the plasma of blood. It plays a crucial role in various physiological processes.

4. **Role of Sodium in the Body**: Sodium is essential for maintaining water balance in the body. It helps regulate blood volume and blood pressure. Sensors in the body, particularly in the kidneys and blood vessels, monitor sodium levels and adjust its excretion accordingly.

5. **Sodium's Function in Nerve and Muscle Cells**: Sodium is also vital for the functioning of nerve and muscle cells. It helps generate electrical signals necessary for nerve impulse transmission and muscle contraction.

6. **Conclusion**: Therefore, the principal cation in the plasma of blood is sodium (Na⁺).

**Final Answer**: Sodium (Na⁺) is the principal cation in the plasma of blood.

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