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.
  Coral reefs are warm, clear, shallow ocean habitats   th â¦ at are rich in life. The reef's massive structure   is formed from coral polyps, tiny animals that live   in colonies; when coral polyps die, they leave behind   a hard, stony, branching structure made of limestone.