The prestige of the nephron

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The second hypostasis of salts: they, or rather their water solutions,electrolytes, decaying into ions in two varieties - with positive charges (cations) and negative (anions). By ion composition of intra - and intercellular fluid sharply differ. There are no collective action of salts is not in sight. The main cation of cells - potassium, and extracellular fluid - sodium. Their movement through the membranes shells defines electrochemical processes underlying the activity of cells,the excitation of nerve, muscle contraction, performance secretory. For these purposes, the cells are equipped with even the sodium-potassium pump.
Not surprisingly, the plasma each anion and cation regulated. Very strictly taken into account reserves of sodium. In a liter of plasma dissolved his 3.3 grams. The increase by two-tenths occurs when the disease, and the fall of concentration per gram incompatible with life.
Maintaining a stable level of sodium in the plasma imputed kidneys in primary obligation. This is the main indicator of their plan on the item. And they set off all sorts of tricks, biochemical combination that their job to do in any circumstances. Until, of course, are in order. Daily blood drops in the kidneys about 600 grams of sodium, but from the body displayed only a few grams, the rest of kidney return. If for some reason a person has to strictly limit the intake of salt (and it is the primary supplier of sodium), even up to half a gram per day (for comparison: a teaspoon - about 10 grams), and then the kidneys are able for a long time to cover the deficit. Reduction of reserves of sodium occurs only 30-40 days, if it was not accidental loss.
The same flexibility, efficiency kidney demonstrate and in maintaining acid-base balance of blood. Depending on the needs of the body the pH of the urine can range from 4.4 to 8.0 units. This is a very wide range: urine sometimes alkaline and acidic and neutral. In plasma, this indicator is 7,35-7,4, and offset it by just 0.4 poses a serious threat to life. So in the bloodstream always ready buffer systems, able to sign in his arms, block extra acidic hydrogen ions. (They otdalyayutsya in water from acids.)
Where to unload the buffer systems? Where to put the former free ions, former troublemakers? The most convenient place - buds. They pumped extra H-ions from the blood, Yes, with what intensity! Their content in the urine may be 800 times more than in the blood. The main levers in this sphere them - again of water and salt.
In the field of water-salt homeostasis the kidneys are very efficient, seeking to combine operations. Often one and the same reaction, the same mechanism levels, closer to the norm and the concentration in the blood osmotically active substances, and the volume of the liquid portion, and electrolyte composition, acid and indicator.
But there is another side of the relationship kidney bloodstream.
At the end of the last century in experiments with extract renal tissue revealed this fact. In animals, which were injected into the bloodstream extract weakened kidneys, a sharply increased blood pressure. The researchers suggested that the kidney allocates a vasoconstrictor agent, and called him - renin. After all, Latin kidney - ren. It took almost four decades, for which the medicine has made great progress in the knowledge of the causes of many diseases, and a series of experimental works immutable revealed the existence of nephrogenic - renal origin - of hypertension.