Definition. The normal concentration of sodium in the blood plasma is 136-145 mM. Hyponatremia occurs when sodium falls below 130 mM. Plasma sodium levels of 125 mM or less are dangerous and can result in seizures and coma. Description. Sodium is an atom, or ion, that carries a single positive charge.
reef1. 1  a ridge of rocks or sand, often of coral debris, at or near the surface of the water. 2  Mining. a lode or vein.
The coral reef off the coast of Queensland, Australia, in the Coral  Sea is the Great Barrier Reef. It is the world's largest reef  system, composed of over 2,900 individualâ¦ reefs and stretches for  over 1,400 miles over an area of about 133,000 square miles.