The reasons of such individual differences

The reasons of such individual differences of osmoregulatory function in many respects are not known. The "adjusting" point of an osmoreceptor is influenced by hemodynamic parametres (see more low), but normal fluctuations of volume or pressure of blood, possibly, are not so great, that into their account it was possible to carry difference in the thresholds varying from 270 to 290 mosmol/kg. Some augmentation of sensitivity buy order ultram of system can be bound with the years, but besides the age factor not unique as even at young faces sensitivity can differ in 5 times. The role of a floor and-or sexual hormones is unknown. In one of researches it has not been found-difference in osmoregulatory function between men and normally menstruating women whereas in other at women and men receiving estrogens sensitivity of system has appeared higher [16]. The osmoreceptor is unequally sensitive to the various substances dissolved in plasma [15, 16, 18]. Sodium and it , in norm of the general osmotic pressure of plasma of 95 defining more, strongest of the known substances stimulating secretion of a vasopressin. Some are rather effective also Saccharum, such, as Mannitolum and sucrose, at least at intravenous introduction. Concerning these substances, thus, the regulation mechanism possesses properties of a true osmoreceptor.
On the other hand, rising of an osmolality of plasma at the expense of urea or a glucose practically does not stimulate vasopressin secretion. Still it is not known, how and why the osmoreceptor so effectively distinguishes different kinds of the substances dissolved in plasma. According to modern representations, a signal stimulating an osmoreceptor, depression of the maintenance of an intracellular liquid under the influence of osmotic forces serves. If this hypothesis is true, ability of the given dissolved substance to stimulate vasopressin secretion should be in inverse relationship from rate from which it gets from plasma to an osmoreceptor [15]. For a long time considered, that this rate of penetration is defined by permeability of a membrane of cells of the osmoreceptor, but recently carried out researches specify in the important role and a hematoencephalic barrier [19]. What was a functional or anatomic basis of specificity of an osmoreceptor, it has the important practical value as limits diagnostic value (see 9-3) to those clinical situations in which level of urea and a glucose in plasma is in norm limits. It means order pyridium online also, that neither the plasma osmolality, nor concentration in it of sodium separately cannot serve as a universal reference point at. to an osmoregulation of secretion of a vasopressin. Ability of other dissolved substances present at plasma (Glycerinum, acetone will not be checked up yet or amino acids) to influence vasopressin secretion, the most reliable approach both in clinical, and in experimental researches there should be a definition of an osmolality of plasma and concentration in it of sodium. Changes of volume or pressure of blood can influence vasopressin secretion also. These hemodynamic influences are mediated basically by the eisodic fibers going from baroreceptors of auricles and an aortic arch and reaching of a brainstem as a part of wandering and glossopharyngeal nerves ( 9-1 see). Exact localisation, number and character of communications by which these signals are transferred in a neurohypophysis, are unknown, but in them, possibly, primary synapses take part in a kernel of a solitary tract of an oblong brain with secondary projections to kernels areas of a back hypothalamus [20]. Functional properties of this hemodynamic system of regulation are presented by dependence between vasopressin level in plasma and changes of arterial pressure ( 9-4). At healthy adult persons sharp depression of arterial pressure by any of several ways led to rising of level of a vasopressin in plasma on size, about corresponding to degree of a reached hypotension. Unlike that that is observed in osmoregulation system, this dependence between stimulus and reaction has distinct diphasic or curvilinear character. So, though episodes of moderately serious hypotension almost always are accompanied very much by substantial increase of level of a vasopressin in plasma, depression of arterial pressure even on 10 usually does not render such effect. Regulation of secretion of a vasopressin at the person is studied by change of volume of blood insufficiently, but the different data received at inspection of the person and in experiment at animals, unanimously specify that mechanisms regulated in the volume react diphasic, or curvilinear image, in the same way, as system [1].