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An electrolyte is a substance containing free ions which behaves as an electrically conductive medium. Because they generally consist of ions in solution, electrolytes are also known as ionic solutions, but molten electrolytes and solid electrolytes are also possible. They are sometimes referred to in abbreviated jargon as lytes.
Electrolytes are normally formed when a salt is placed into a solvent such as water and the individual atomic components are separated by the force applied upon the solute molecule, in a process called chemical dissociation in which the solution applies force to hold the ions apart. Salts are compounds that are linked by weak ionic bonds, and will separate into charged ions in the presence of a solution containing stronger covalent bonds.
An electrolyte may be described as concentrated if it has a high concentration of ions, or dilute if it has a low concentration. If a high proportion of the solute] dissociates to form free ions, the solution is strong; if most of the solute does not dissociate, the solution is weak. The properties of electrolytes may be exploited using electrolysis to extract constituent elements and compounds contained within the solution.
In physiology, the primary ions of electrolytes are sodium(Na+), potassium (K+), calcium (Ca++), magnesium (Mg++), chloride (Cl-), phosphate (PO4---), bicarbonate (HCO3-) and Zinc . The electric charge symbols of plus (+) and minus (-) are used to indicate that the substance indicated is ionic in nature and has an imbalanced distribution of electrons. This is the result of chemical dissociation.
All higher lifeforms require a subtle and complex electrolyte balance between the intracellular and extracellular enveiroments. In particular, the maintenance of precise osmotic gradients of electrolytes is important. Such gradients affect and regulate the hydration of the body, blood pH, and are critical for nerve and muscle function.
Both muscle tissue and neurons are considered electric tissues of the body. Muscles and neurons are activated by electrolyte activity between the extracellular fluid or interstitial fluid, and intracellular fluid. Electrolytes may enter or leave the cell membrane through specialized protein structures embedded in the plasma membrane called ion channels. For example, muscle contraction is dependent upon the presence of calcium (Ca++), sodium (Na+), and potassium (K+). (See muscle contraction) Without sufficient levels of these key electrolytes, muscle weakness or severe muscle contractions may occur.
Electrolyte balance is maintained by oral, or in emergencies, intervenous (IV) intake of electrolyte-containing substances, and is regulated by hormones, generally with the kidneys flushing out excess levels. In humans, electrolyte homeostasis is regulated by hormones such as antidiuretic hormone, aldosterone and parathyroid hormone. Serious electrolyte disturbances, such as dehydration and overhydration, may lead to cardiac and neurological complications, and unless they are rapidly resolved will result in a medical emergency.
Measurement of electrolytes is a commonly performed diagnostic procedure, performed via blood testing or urinalysis. The interpretation of these values is somewhat meaningless without analysis of the clinical history, and is often impossible without parallel measurement of renal function. Electrolytes measured most often are sodium and potassium. Chloride levels are rarely measured except for arterial blood gas interpretation, as they are inherently linked to sodium levels. One important test conducted on urine is the specific gravity test to determine the occurrence of electrolyte imbalance.
In oral rehydration therapy, electrolyte drinks containing sodium and potassium salts are used to replenish the body's water and electrolyte levels after dehydration caused by exercise, diaphoresis, diarrhea, vomiting or starvation. Giving pure water to such a person is not the best way to restore fluid levels, because it dilutes the salts inside the body's cells and interferes with their chemical functions. This can lead to water intoxication.
Sports drinks such as Gatorade or Lucozade are electrolyte drinks with large amounts of added carbohydrates, such as glucose, to provide energy. The drinks commonly sold to the public are isotonic (with osmolality close to that of blood), with hypotonic (with a lower osmolality) and hypertonic (with a higher osmolality) varieties available to athletes, depending on their nutritional needs.
It's really not necessary to replace losses of sodium, potassium and other electrolytes during exercise since you're unlikely to deplete your body's stores of these minerals during normal training. If, however, you find yourself exercising in extreme conditions over 5 or 6 hours (an Ironman or ultramarathon, for example) you will need to add a complex sports drink with electrolytes. Athletes who don't consume electrolytes under these conditions risk overhydration (or hyponatremia). 
Because sports drinks contain very high levels of sugar, they are not recommended for regular use by children. Rather, specially-formulated pediatric electrolyte solutions are recommended. Sports drinks are also not appropriate for replacing the fluid lost during diarrhea. The role of sports drinks are to inhibit electrolyte loss, but are insufficient to restore imbalance once it occurs. Medicinal rehydration sachets and drinks are available to replace the key electrolyte ions lost. Dentists recommend that regular consumers of sports drinks observe precautions against tooth decay.
Electrolyte and sports drinks can be home-made by using the correct proportions of sugar, salt and water. 
- Chemical elements
- Strong electrolyte
- Weak electrolyte
- Reference ranges for blood tests
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