Distinguish following mechanisms of return of heat in environment radiation, теплопроведение, конвекцию and evaporation. Radiation is a return of heat in the form of electromagnetic waves of an infra-red range effexor xr tapering 5 – 20 microns. All subjects with temperature above absolute zero -273S give energy by radiation. Electromagnetic radiation freely passes through vacuum, also it is possible to consider atmospheric air transparent for electromagnetic waves.
The quantity of heat disseminated by an organism in environment by radiation, is proportional to the area of a surface of studying the area of a surface of those parts of a body, которыесоприкасаются with air and differences of average values of temperatures of a skin and environment. At ambient temperature 20С and relative humidity of air 40 – 60 the organism of the adult person disseminates by radiation nearby effexor impotence – 50 of all given heat.
Radiation from a body surface increases at rise in temperature of a skin and decreases at its fall. If temperatures of a surface of a skin and environment are levelled, return of heat by radiation stops. If ambient temperature exceeds skin temperature, the body of the person is warmed, absorbing the infra-red beams allocated with the environment. Теплопроведение
– heat return at direct
of a body with other physical objects.
Dry air, fatty fabric are characterised by low heat conductivity and are heat insulators. Damp air sated with water steams, water have высокуютеплопроводность. Therefore stay at low temperature in the environment with high humidity is accompanied by strengthening теплопотерь an organism. The damp clothes lose the теплоизолирующие properties. Конвекция – теплоотдача, carried out by heat carrying over by moving particles of air water. Konvektsionnyj heat exchange, unlike теплопроведения, is connected with an exchange not only energy, but also molecules.
It occurs because round all subjects there is air or liquid interface which thickness effexor impotence on surrounding conditions. When the body is surrounded by motionless air, warm air which, passing in air departs from a skin, transfers both energy, and molecules. Such process is called as free конвекцией.
If air moves, the thickness of an interface depends on speed of movement of air. The interface equal at motionless air to several millimetres, at a wind can decrease to several microns. Heat exchange of this kind substantially depends on speed of movement of air and is called as compulsory конвекцией. For heat dispersion конвекцией the flow generic effexor price a surface of a body a stream of air with lower temperature is required.
Layer of air directly contacting to a skin heats up, reduces the density, rises and replaced with colder and dense air. In conditions when air temperature is equal 20С, and relative humidity – 40 – 60the body of the adult person disseminates in environment by теплопроведения and конвекции nearby 25 – 30 of heat.
The effexor xr online pharmacy given конвекцией heat increases at increase of speed of movement of air streams a wind, ventilation.
Evaporation is a return of heat in environment at the expense of evaporation of sweat or a moisture from a surface of a skin and mucous respiratory ways.
At environment temperature nearby 20С evaporation makes nearby 36 гч. 0,58 kcal of thermal energy are spent For evaporation 1 г waters, i. by evaporation the human body gives in these conditions about 20 of all disseminated heat. Increase
external temperature, physical activity performance strengthen потоотделение, and it can increase to 500 – 2000 гч.
If the external temperature exceeds average value of temperature of a skin the organism cannot give to environment warmly radiation, конвекцией and теплопроведением, therefore
of evaporation of a moisture from a body surface becomes unique way of dispersion of heat. Such evaporation is possible until humidity of air of environment remains less than 100. At intensive потоотделении, high humidity and small speed of movement of air of a droplet of sweat, without having time to evaporate, flow down from a body surface, теплоотдача by evaporation becomes less effective.
Body temperature of the person and its measurement Body temperature гомойотермных organisms is difficult function теплопродукции in different fabrics, carrying over of heat as a result of blood circulation and local temperature gradients. As heat is given to environment mainly through a skin, temperature of superficial fabrics cover, as a rule, below temperature of deeper fabrics kernel.
In concept гомойотермное the kernel is included by the fabrics of a human body located on effexor impotence 1 sm from a surface and more. The temperature of superficial effexor impotence is non-uniform it above on the sites of a body well supplied with blood or closed by clothes, i.
depends, on the one hand, on intensity of carrying over to it of heat blood, and with another – from cooling or warming action of temperature of environment. In extremities there is a longitudinal axial temperature gradient and radial perpendicular surfaces a temperature gradient.
In connection with non-uniformity of geometrical forms of a human body spatial distribution of body temperature is described by difficult three-dimensional function. For example, when easily dressed person is in a premise with air temperature 20С, the temperature of a deep muscular part of a hip makes approximately 35С, temperature of deep layers икроножной muscles 33С, and in the foot centre only 27 – 28С.
The temperature of deep fabrics of a body is distributed in regular more intervals and makes nearby 36,7-37,0S fig. effexor impotence picture i_029. jpg Kernel temperature – one of the major constants of the homeostasis, defining speed of biochemical reactions, конформационные changes of biologically important molecules, аследовательно, and level of activity of all cages of an organism. However and it is not a constant neither in spatial, nor in the time effexor impotence.
Even in a brain there is a radial temperature gradient more than in ГС from the central part to a bark. Daily fluctuations of internal temperature in conditions относительногопокоя are in limits ГС. The maximum value body temperature reaches in 18 – 20 hours and decreases to the minimum during a night dream, to 4-6 oclock in the morning.
Daily effexor impotence of temperature of a kernel are based on эндогенном a rhythm internal clocks which is usually synchronised with external gauges of time. During travel with crossing of terrestrial meridians it is required 1 – 2 weeks that the temperature rhythm effexor xr review> come to conformity with local time.