structural:reformatting, information:filtering, structural:expansion, stylistic:tone
Physiological importance

Both muscle tissue and neurons are considered electric tissues of the body. Muscles and neurons are activated by electrolyte activity between the extracellular fluid or interstitial fluid, and intracellular fluid. Electrolytes may enter or leave the cell membrane through specialized protein structures embedded in the plasma membrane called " ion channels ". For example, muscle contraction is dependent upon the presence of calcium (Ca), sodium (Na), and potassium (K). Without sufficient levels of these key electrolytes, muscle weakness or severe muscle contractions may occur.