Water-electrolyte balance

Of the Water-electrolyte balance of organisms is crucial for the normal course of all biochemical processes. The chemical reactions necessary for life only take place in an aqueous environment. The fluid distribution in the body is regulated by electrolytes. The water-electrolyte balance includes water and the electrolytes dissolved in it.

What is the water-electrolyte balance?

Life arose in the sea, which from the beginning had a certain concentration and composition of electrolytes. Even after the organisms left the ocean as part of evolution, water and the dissolved salts continued to play an essential role in biochemical processes.

The human organism consists of around 60 percent water. Various salts are dissolved in the water, which are known as electrolytes.

The body is made up of cells. Therefore, the whole organism is divided into different rooms. The best known is the division into the inner-cellular and the extra-cellular space. Both spaces are separated from each other by cell membranes. There are important differences in the composition of the electrolytes between the intracellular space (intracellular space) and the extracellular space (extracellular space). These differences are permanently maintained by active transport processes through the cell membranes.

Since water can diffuse through the cell membranes, but the ions of the electrolytes only get through the membranes by active pumps, a so-called osmotic pressure is established. Despite the different composition of the liquid in the different rooms (compartments), the osmotic pressure is equalized.

Function & task

There is constant exchange between the various compartments. With a balanced water-electrolyte balance, there are constant potential differences between the inner-cellular space and the extra-cellular space, since the electrolyte composition is different in these two spaces.

The electrolytes include the positively charged cations of sodium, potassium, calcium or magnesium and the negatively charged anions of phosphate, bicarbonate or chloride. There are other negatively charged ions of organic compounds such as proteins.

The different composition of the fluid inside and outside of the cells ensures that important reactions run smoothly, which can only take place under certain conditions. Through the so-called sodium channel within the membranes, sodium and chloride ions are mainly transported into the extracellular space and potassium and phosphate ions or negatively charged proteins into the inner cellular space. Only in this way can the most important biochemical processes take place within the cell. There are cell organelles in the cell, which in turn form their own spaces and are separated from the cytoplasm by membranes.

Overall, a potential difference develops between the inner cellular space and the extracellular space due to the different concentration distribution. Changes in concentration ensure the exchange of information between the cells. In this way information can be passed on which is important for the interaction of the cells.

In addition, the electrolytes ensure both the fluid distribution in the body and the undisturbed flow of biochemical processes at cell level. In addition, they also play an important role in the transmission of stimuli in the nerve cells.

The extracellular space is divided into the interstitial space and the intravascular space. The intravascular space contains the fluid in the blood and lymph vessels. The interstitial space is the space between the individual cells. Two thirds of the total body water is in the cells and thus one third outside the cells. Of this third, three quarters of the fluid is in the interstitial space, while the intravascular space contains a quarter of the water in the extracellular space.

The water-electrolyte balance is maintained through the daily intake of water and electrolytes through food and drinks. The body should be given about 2.5 liters of fluid. The excretion of fluids and electrolytes occurs mainly through the kidneys. However, a large part is also lost through sweating and breathing.

The personal composition of the nutrients should ensure that the required amount of electrolytes is absorbed through food.

Illnesses & ailments

Disturbances in the water-electrolyte balance can lead to serious illnesses. In the case of kidney disease or in certain extreme situations, the body's own regulation of the water-electrolyte balance can collapse. In addition to kidney diseases, this is the case with severe diarrhea, vomiting, blood loss, profuse sweating or dehydration due to thirst.

The various diseases can lead to dehydration, but also hyperhydration, hypo- or hypervolaemia, hypo- or hypernatremia, hypo- or hyperkalaemia and hypo- or hypercalcemia. All of these conditions cause the breakdown of the normal potential between the inner-cellular space and the extra-cellular space. A life-threatening situation can arise which must be treated with an appropriate electrolyte infusion.

The water-electrolyte balance system is controlled by various mechanisms. These include the thirst mechanism, the renin-angiotensin-aldosterone system, the antidiuretic hormone or peptides that act on the kidneys. A disturbance within these mechanisms can lead to serious disturbances of the water-electrolyte balance.

The sodium ion is one of the most important ions that maintain the entire electrolyte and fluid balance. With hyponatremia (too low sodium concentration), for example, muscle cramps, disorientation, lethargy or even coma can occur. Depending on the specific cause, sodium must be substituted in these cases. The symptoms of hypernatremia (too high a sodium ion concentration) are often unspecific and manifest themselves in feelings of weakness and neurological deficits. The treatment is carried out, for example, by low-sodium hydration.