This information is about Sodium (Natrium) and body fluids....
Sodium chloride, also known as salt, common salt, table salt or halite, is an ionic compound with the formula NaCl, representing equal proportions of sodium and chlorine. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms. In the form of edible or table salt it is commonly used as a condiment and food preservative.
Sodium is a chemical element with the symbol Na (from Latin: natrium) and atomic number 11. It is a soft, silver-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. The free metal does not occur in nature, but instead must be prepared from its compounds; it was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. Sodium is the sixth most abundant element in the Earth's crust, and exists in numerous minerals such as feldspars, sodalite and rock salt (NaCl). Many salts of sodium are highly water-soluble, and their sodium has been leached by the action of water so that sodium and chlorine (Cl) are the most common dissolved elements by weight in the Earth's bodies of oceanic water.
Many sodium compounds are useful, such as sodium hydroxide (lye) for soap-making, and sodium chloride for use as a de-icing agent and a nutrient (edible salt). Sodium is an essential element for all animals and some plants. In animals, sodium ions are used against potassium ions to build up charges on cell membranes, allowing transmission of nerve impulses when the charge is dissipated. The consequent need of animals for sodium causes it to be classified as a dietary inorganic macro-mineral.
In humans, sodium is an essential nutrient that regulates blood volume, blood pressure, osmotic equilibrium and pH; the minimum physiological requirement for sodium is 500 milligrams per day. Sodium chloride is the principal source of sodium in the diet, and is used as seasoning and preservative, such as for pickling and jerky; most of it comes from processed foods. The DRI for sodium is 2.3 grams per day.
The renin-angiotensin system regulates the amount of fluids and sodium in the body. Reduction of blood pressure and sodium concentration in the kidney result in the production of renin, which in turn produces aldosterone and angiotensin, retaining sodium in the urine. Because of the increase in sodium concentration, the production of renin decreases, and the sodium concentration returns to normal. Sodium is also important in neuron function and osmoregulation between cells and the extracellular fluid.
More about body fluids and Salt balance.....
The renin-angiotensin system and the atrial natriuretic peptide indirectly regulate the amount of signal transduction in the human central nervous system, which depends on sodium ion motion across the nerve cell membrane, in all nerves. Sodium is thus important in neuron function and osmoregulation between cells and the extracellular fluid. Hence, sodium is the most prominent cation in extracellular fluid: the 15 liters of it in a 70 kg human have around 50 grams of sodium, 90% of the body's total sodium content.
Whenever there is an increase in sodium concentration in the blood, the kidney releases most of it in order that there will be enough water for use of the body. But when there is a decrease in its concentration, there is more release of water to store more sodium which the body needs dearly. This process is known as osmo-regulation.
Sodium is the primary cation (positive ion) in extracellular fluids in animals and humans. These fluids, such as blood plasma and extracellular fluids in other tissues, bathe cells and carry out transport functions for nutrients and wastes. Sodium is also the principal cation in seawater, although the concentration there is about 3.8 times what it is normally in extracellular body fluids.
Although the system for maintaining optimal salt and water balance in the body is a complex one, one of the primary ways in which the human body keeps track of loss of body water is that osmo-receptors in the hypothalamus sense a balance of sodium and water concentration in extracellular fluids. Relative loss of body water will cause sodium concentration to rise higher than normal, a condition known as hypernatremia. This ordinarily results in thirst. Conversely, an excess of body water caused by drinking will result in too little sodium in the blood (hyponatremia), a condition which is again sensed by the hypothalamus, causing a decrease in vasopressin hormone secretion from the anterior pituitary, and a consequent loss of water in the urine, which acts to restore blood sodium concentrations to normal.
Severely dehydrated persons, such as people rescued from ocean or desert survival situations, usually have very high blood sodium concentrations. These must be very carefully and slowly returned to normal, since too-rapid correction of hypernatremia may result in brain damage from cellular swelling, as water moves suddenly into cells with high osmolar content.