The water-electrolyte balance of organisms is crucial for the normal functioning of all biochemical processes. The chemical reactions necessary for life occur only in an aqueous environment. In this context, the distribution of fluids 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?
The water-electrolyte balance includes water and the electrolytes dissolved in it. Life originated in the sea, which had a certain concentration and composition of electrolytes from the beginning. Even after organisms left the ocean during evolution, water and the dissolved salts continued to play an essential role in biochemical processes. For example, the human organism is composed of approximately 60 percent water. Dissolved in water are various salts, which are called electrolytes. The body consists of cells. Therefore, the whole organism is divided into different spaces. The best known is the division into the intracellular and the extracellular space. Both spaces are separated from each other by cell membranes. Between intracellular space (intracellular space) and extracellular space (extracellular space) there are important differences in the composition of electrolytes. 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 can only pass through the membranes by active pumping, a so-called osmotic pressure is established. Despite differences in the composition of the fluid in the different spaces (compartments), the osmotic pressure balances out.
Function and task
There is a constant exchange between the different compartments. In a balanced water-electrolyte balance, there are constant potential differences between the intracellular space and the extracellular space because the electrolyte composition in these two spaces is different. Electrolytes include the positively charged cations of sodium, potassium, calcium or magnesium and the negatively charged anions of phosphate, bicarbonate or chloride. Other negatively charged ions of organic compounds such as proteins also exist. The different composition of the fluid inside and outside the cells ensures the undisturbed course of important reactions that can only take place under certain conditions. Through the so-called sodium channel within the membranes, sodium as well as chloride ions are mainly transported into the extracellular space and potassium as well as phosphate ions or negatively charged proteins into the intracellular space. This is the only way that the most important biochemical processes can take place within the cell. In the cell there are cell organelles, which in turn form their own spaces and are separated from the cytoplasm by membranes. Overall, a potential difference is formed between the intracellular space and the extracellular space due to the different concentration distribution. Changes in concentration provide for the exchange of information between cells. In this way, information can be transported further, which is important for the interaction of the cells. In addition, through the electrolytes, both the fluid distribution in the body and the undisturbed course of biochemical processes at the cellular level are ensured. Furthermore, they thus 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 includes the fluid in the blood and lymph vessels. The interstitial space is the space between individual cells. Two-thirds of the total body fluid is inside the cells and thus one-third is outside the cells. Of this third, the interstitial space in turn contains three-quarters fluid, while the intravascular space contains one-quarter of the water found in the extracellular space. The water-electrolyte balance is maintained by the daily intake of water and electrolytes through food and beverages. At the same time, the body should be supplied with approximately 2.5 liters of fluid. The excretion of fluid and electrolytes occurs mainly through the kidneys. However, a large part is also lost through sweating and respiration.Personal composition of nutrients should ensure that the required amount of electrolytes is absorbed through food.
Diseases and ailments
Disturbances of the water-electrolyte balance can lead to serious diseases. In diseases of the kidneys or in certain extreme situations, the body’s own regulation of the water-electrolyte balance can break down. In addition to kidney diseases, this is the case, for example, with severe diarrhea, vomiting, blood loss, heavy sweating or dehydration due to thirst. The various diseases can lead to dehydration, but also to hyperhydration, hypo- or hypervolemia, hypo- or hypernatremia, hypo- or hyperkalemia and hypo- or hypercalcemia. All of these conditions cause the breakdown of the normal potential between the intracellular space and the extracellular space. A life-threatening situation may occur, which must be treated by appropriate electrolyte infusion. The system of water-electrolyte balance is controlled by several mechanisms. These include the thirst mechanism, the renin-angiotensin-aldosterone system, antidiuretic hormone or renal peptides. Disruption within these mechanisms can cause serious disturbances in water-electrolyte balance. For example, sodium ion is among the most important ions that serve to maintain overall electrolyte and fluid balance. In the case of hyponatremia (insufficient sodium concentration), for example, muscle cramps, disorientation, lethargy or even coma occur. Depending on the specific cause, sodium must be substituted in these cases. The symptoms of hypernatremia (excessive sodium ion concentration) are often nonspecific and manifest as feelings of weakness and neurological deficits. Treatment includes low-sodium fluid supplementation.
