Biology subjects

Yuri Kamnev

Publications and source records attributed to Yuri Kamnev.

4 recordsLinked to original sources

bioRxiv2016

Frank-Starling law and Bowditch phenomenon may have the common theoretical grounds

The relationship between two different linear dimensions of the chamber (ventricle) and the two respective values of the force of contraction (which are applied to the imaginary piston in order to accelerate the initial venous inflow) is deduced as the ratio of forces which is equal to the ratio of squares of linear dimensions of the chamber; the equation is valid when the durations of both contractions (systoles) are identical. The relationship corresponds to Frank-Starling law (the right limb of parabola can be approximated to the direct proportionality of the law). When the durations of systoles are different the ratio of forces is equal to the inverse ratio of durations of systoles; the inverse proportionality permits to interpret the Bowditch phenomenon by means of the ascending asymptote of hyperbole. Stepwise shortening of systole is impossible due to extremely narrow range of variable (duration of systole), hence the shift of variable can be realized only as a leap; this leap is accompanied by the enormous rise of function (force of contraction) which can be accommodated to several contractions. Homoiometric regulation can be considered a safety device (presumably in the form of paroxysmal tachycardia with the shortened systole) in the case when heterometric regulation lacks to produce the adequate force of contraction in response to excessively distended chamber.

Physiology↗

bioRxiv2016

The view of the native gauges of blood pressure - focus on atrium (hydrodynamics and rheology)

The precision of the inlet parameters depends on mechanism of response. Reflexes are satisfied with relative higher or lower but if the inlet information is presented by different parameters and the response is calculated according to some equation precision must reach the degree which does not slur over the results of calculation. At recent work the equation for controlling of circulation was suggested where the main inlet parameters are the arterial diastolic and vinous pressures and it becomes pertinent to analyze how organism can perceive these pressures with hydrodynamic accuracy. As far as the velocity pressure component of total pressure can not be detected by wall receptor of the rectilinear section of artery it was noticed that baroreceptors are located at the outer radius of the bend of central arteries and that is justified due to specific distribution of pressure. This phenomenon can be interpreted as a correction of measuring of static pressure with regard for velocity pressure component. Velocity pressure component of venous pressure is comparable with the one of arterial pressure but static components of venous and arterial pressures are incomparable and it is the fact that cannot be ignored when choosing the gauge. The possible method of measuring of pressure is based on observation that pressure-volume vector of the ventricular cycle is similar to a-loop vector of atrial cycle. Ventricular filling vector and x-trough vector show the behavior of viscous material but v-loop inserted into a-loop demonstrates typical viscoelasticity with creep. If viscous deformation of atrium at early relaxation possesses standard duration being stopped by transformation of viscous deformation into viscoelastic deformation the venous pressure can be measured in accordance with the value of viscous deformation. Measuring of pressure by viscous method implemented by atrium has the advantage comparing to measuring by baroreceptor with elastic sensor. Early relaxation of atrium which reveals coefficient of viscosity corresponds to ventricular relaxation and its coefficient of viscosity but the latter is liable to different biochemical shifts. Such shifts influences the atrial coefficient of viscosity either and the values of venous pressure measured by viscous method will be more accurate for calculations because coefficient of viscosity participates in the equation being not estimated in organism.

Physiology↗

bioRxiv2014

The conversion of systolic volume into systolic pressure (the development of numerical model)

The direct proportional trend of the transition from systolic volume to systolic pressure can be proved theoretically with the help of circulatory numerical model. The model permits to link calculable end-diastolic volume with the observable interrelations between systolic and diastolic pressures. The outstripping growth of systolic pressure (when diastolic pressure is rising with steady increment) is deduced and the analogous phenomenon can be observed at clinical gradation of arterial hypertension.

Physiology↗

bioRxiv2014

Viscous deformation of relaxing ventricle and pulsatile blood propelling (numerical model)

The numerical model of one-loop circulation exploits viscous deformation as mechanism of ventricular filling. Mathematical advantage of viscous deforming is a possibility to present the ventricular filling as the function of two independent variables (stress and time); two-dimensional argument frames a table which permits to calculate end-diastolic ventricular volume due to information about measured venous pressure and duration of ventricular diastole. The equation was deduced which balances the system while varying of such parameters as arterial resistance, the value of normal rhythm and the volume flow rate. The model pays attention on the phenomenon of asymmetrical position of normal rhythm (the steady rhythm in conditions of rest) and explains why the operating range of brady-rhythms is much narrower than the operating range of tachy-rhythms.

Physiology↗