Fluid and Electrolyte Balance in the Body

Intracellular

Fluid inside the cell 2/3

Extracellular

Fluid outside the cell ⅓

Interstitial

Fluid surrounding the cell

Intravascular

Fluid within blood vessels

Electrolytes

The movement and balance of water in the areas around a cell is maintained by electrolytes.

Water Roles

Carries nutrients and waste products, maintains structure of large molecules, participates in metabolic reactions, serves as a solvent, acts as a lubricant and cushion, aids in regulation of body temperature, maintains blood volume and influences blood pressure.

Calcium Roles

Helps maintain normal blood pressure, grow healthy skeleton in early life, helps minimize bone loss in later life, helps continuously remodel, has calcium bank.

Extracellular Calcium

Participates in blood clotting.

Intracellular Calcium

Regulation of muscle contraction, transmission of nerve impulses, secretion of hormones, activation of some enzyme reactions.

Phosphorus Roles

Part of major buffer system, part of DNA and RNA, assists in energy metabolism, helps transport lipids in the blood, structural component of cell membranes.

Potassium Roles

Principal intracellular cation, helps maintain fluid and electrolyte balance, helps maintain cell integrity, aids in nerve impulse transmission and muscle contraction.

Sodium Roles

Principal cation of extracellular fluid (primary regulator of volume), acid-base balance, nerve impulse transmission, muscle contractions.

Chloride Roles

Essential nutrient, part of hydrochloric acid, helps maintain fluid and electrolyte balance, moves passively across membrane, associates with sodium and potassium, major anion of extracellular fluids.

Magnesium Roles

Maintains bone health, necessary for energy metabolism, catalyst in ATP production, inhibits muscle contraction.

Electrolytes

Salts that dissolve in water and separate into cations and anions.

ADH

Signaled by hypothalamus, released by pituitary gland.

Renin

Enzyme released by kidney cells when blood pressure is too low.

Aldosterone

Regulates blood pressure and blood volume (controls balance of sodium and potassium).

Kidney

Excrete potassium and retain sodium when sodium is low.