The lower boundary of the exosphere is called the exobase. It is also called exopause and 'critical altitude' as this is the altitude where barometric conditions no longer apply. Atmospheric temperature becomes nearly a constant above this altitude.
Sodium â the volatility and solvent mineral: essential to life, all body fluids contain sodium â itâs needed for many biochemical processes including water balance regulation, fluid distribution on either side of the cell walls, muscle contraction and expansion, nerve stimulation and acid-alkaline balance.
The kidneys help keep extracellular fluid from becoming too dilute or concentrated with respect to the solutes carried in the fluid. 3. Regulation of ion concentrations. The kidneys are responsible for maintaining relatively constant levels of key ions including sodium, potassium and calcium.