Final answer:
The primary intracellular cation is potassium (K⁺), which plays a crucial role in establishing the resting membrane potential in neurons and muscle fibers.
Step-by-step explanation:
The primary intracellular cation is potassium (K⁺).
Potassium is the major intracellular cation, playing a crucial role in establishing the resting membrane potential in neurons and muscle fibers. It helps regulate body fluids and cell functions.
Other important cations in body fluids include sodium (Na⁺), calcium (Ca²⁺), and magnesium (Mg²⁺). Sodium is present in fluids inside the cells, while calcium and magnesium are primarily present in the body fluids outside the cells, contributing to muscle contraction, nerve control, and enzyme functions.