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.
For other senses of this word, see atoll (disambiguation). An atoll (pronunciation: /ËÃ¦tÉl/, /ËÃ¦tÉËl/, /ËÃ¦toÊl/, /ÉËtÉl/, /ÉËtÉËl/ or /ÉËtoÊl/), sometimes called a coral atoll, is a ring-shaped coral reef including a coral rim that encircles a lagoon partially or completely. There may be coral islands/cays on the rim.