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a heart rhythm and its physiological characteristics

It is known, that in a myocardium except sokratitelnyh, or workers, fibres there is a special system of the muscular units possessing ability to generation of spontaneous rhythmic activity, a spread of activation to all muscular layers and coordination of sequence of reduction of chambers of heart (N.A.Agadzhanjan other, 2001).

These specialised muscular fibres compound conductive system of heart in which arises, and then and extends, the excitation conducting to its reduction. The conductive system consists from anatomicheski konturirovannogo, specific, intrakardialnogo formations. Knots of conductive system consist of the dense delimited network of the cages closely bound to a clump of the excitatory and fibrillar elements, forming sinoatrialnyj knot (knot Kiz-Fleka) or the main centre of the automaticity of heart - pejsmeker the first order with various excitability of head and tail its parts (M.R.Sapin, Z.G.Bryksina, 1995).

Any choronomic influence invokes the change of a heart rhythm which is carried out through knot Kiz-Fleka pejsmejkernoj of system of heart (V.I.Prosheva, 1998) for which are characteristic a uniform rhythm and full
Synchronisation of separate elements. According to I.V.Muhinoj, etc. (2001), there are two hypotheses of synchronisation. According to the first hypothesis presented in due time R.M.Baevskim (1968, 1984), as a result of change of various biophysical conditions the role pejsmekera passes from one cage of sinus knot to another while the others are depressed. If function is incurred by cages of the top part of sinus knot (vysokovozbudimye) duration of a cardial cycle (DSTS) decreases. At a bradycardia pejsmekernuju function is carried out by the inferior part of sinus knot, and in the conditions of physiological norm - cages of its central part, and in the course of synchronisation not last role is played by parasympathetic control. Besides, the general rhythm pejsmekernoj fabrics and hearts as a whole is formed as a result of bioelectrical interaction between elements pejsmekera, initially discharged in different frequencies that leads to formation of a new, mediate rhythm (Island E. Osadchy, 1991; N.A.Alipov, 1993).

From sinoatrialnogo knot excitation extends to working cages of a myocardium of auricles diffusively and on special intracardiac conducting bundles. Both streams reach the second knot - not less important place possessing ability to generate impulses, - atrioventrikuljarnogo knot (Ashof-Tavara). It is located in thickness of a warm septum on border of auricles and ventricles. The knot consists from three possessing own frequency of excitation of parts: top (atrial), average and inferior (zheludochkovoj). This knot is pejsmekerom the second order, and excitation through it in normal conditions can pass only in one direction. Thus impulses are late on 0,02-0,04с - an atrio-ventricular delay phenomenon that does not contradict the law of secund carrying out of impulses on a nerve. For this time the ventricular systole has time to come to the end, and their fibres will be in a phase refrakternosti thanks to what auricles receive sufficient time for pushing through in ventricles of blood containing in them.

The third level providing rhythmic activity of heart, is located in a ventriculonector and fibres Purkine (A.M.Sigal, 1958). The Ventriculonector, as is known, originates from predserdno-zheludochkovogo knot and forms two legs: right (longer), being as though continuation of all fascicle, - for the right ventricle, and left (shorter) - for a left ventricle.

The left leg departs from the general ventriculonector above, than right, rhipidately breaking up with the most beginning and widely branching in endokarde to the left side of a septum the superficial branches. Other branches it goes to a forward and back papillary muscle, and two is deeper the located branches - to a heart top, breaking up on smaller branches, and then on dense network Purkine. The right leg located in the top third it is superficial (under endokardom), in average passes in thickness of a septum, and in inferior again it is more superficial; Later it breaks up to three branches, and then, as well as left, on a dense network of fibres Purkine which is settling down under endokardom of both ventricles (E.B.Babsky, h.p. Uljaninsky, 1970).

The centres of the automaticity located in conductive system of ventricles, carry the name pejsmekerov the third order, and excitation on ventriculonector legs goes to a heart top where on branchings of legs and fibres Purkine comes back to its establishment. As a result of it heart reduction as a whole is carried out in certain sequence: auricles, tops of ventricles and, at last, their establishment.

Activity of the most complicated central member of a circulation - hearts - is characterised in norm by exclusive coordination and co-ordination of its mechanisms providing a normal circulation and continuous progression of blood in one direction on vascular system. Excitation impulses, ritmicheski arising in sinoatrialnom knot, are transferred on conductive system with certain speed, a little being late in atrioventrikuljarnom knot, as
Causes exact sequence in reductions of both departments of heart - auricles and ventricles, them always non-simultaneous oporozhnenie and consequently filling not quite coinciding on time by their blood (G.I.Kositsky, 1977). Reductions of the departments of heart with the same name, right and its left half, descend synchronously and, alternating with a stage of their release phenomenon, koordinirovany to mechanism of consecutive closure faultlessly functioning in norm and discoverings of both pairs (atrioventrikuljarnyh and semilunar) valves. Such is the mechanism of automatic work of reductions of heart following one after another with a systole and a diastole, generating the sound phenomena with pauses between them, that develops in this or that heart rhythm (RS) when three-level pejsmeker hearts the rhythmic drawing (forms V.V. Parin, etc., 1966 - 1969; R.M.Baevsky, 1984). Last years data that along with existence of intracardiac generator RS there is also a generator in the central excitatory system - in efferentnyh frames of the warm centre of myelencephalon (V.G.Abushkevich, etc., 2001 are obtained; V.M.Pokrovsky, 2005).

The deflection from accuracy and correctness in alternating of warm reductions irrespective of, whether is ascertained it throughout rather short interval of time or more long, testifies to infringements of rhythmic activity of heart, i.e. about aritmii (V.M.Zatsiorsky, S.K.Sarsanija, 1968). Warm aritmii, arising owing to infringement of various functions of a cardiac muscle, but mainly excitability and conductivity functions, differ considerable variety. According to given following kinds aritmii exist A.M.Sigala (1958):

1) sinusovye aritmii, proceeding mostly as bradiaritmii, and their types, in particular, respiratory aritmija, ascertained in communication and depending on breath phases;

2) ekstrasistolicheskaja aritmija, for which auskultiruemaja an extrasystole with characteristic for it the premature enhanced
Reduction and following it kompensatornoj a pause is the main defining rhythmic sign;

3) alloritmija - the rhythm broken in the correctness where the cycles consisting of two and more rhythmic elements, abjointed by more long pause, alternate in certain natural sequence, i.e. an "irregular" rhythm in which, however, probably to catch known law;

4) full (absolute) aritmija which basis is blinking or one of types of trembling of auricles, - so-called vibrating aritmija;

5) the special forms bradiaritmii, differing absence kompensatornoj pauses and some other signs. They rather meet less often and at the heart of them infringements of warm conductivity (transmissornye bradiaritmii), and also sinusovogo automatism lay mostly.

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Scientific source GORSHKOVA Marina Nikolaevna. Individual and group indicators of a heart rhythm at its mediated control. The dissertation on competition of a scientific degree of a Cand.Biol.Sci. Tver - 2015. 2015

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