The ability known as thermoregulation is a feature of an organism that help to keep the body temperature within certain thresholds, thus independently from external conditions. A dynamic state of thermal balance of human body between its internal environment and the territory is a model example of precise control of organism heat. In the case where such stability would be disturbed the immediate response would appear as well. In accordance with the thermodynamic principles the flow of the heat will occur without change of the state (Houdas and Ring, 1982). Moreover, temperature coordination is closely related to the changes within the cardiovascular system as well. To support above theory the effects of low temperature on blood pressure and pulse were measured. These as main formulas of the body’s internal status by their continuous inconsistency are not only responsible for maintaining homeostasis within an organism but for regulation of a heat response as well. An assumption supported an antagonistic character of dependence between these cooperating factors. An application of cold water to the limb, thus method used during the experiment has reflected a factual interaction between low temperature and the body. Results supported founded predictions. Therefore, whenever the temperature dropped the blood pressure has raised. Sudden and distinct changes in external conditions have an impact on internal structure operation character.
An adjustment of a blood flow in connection to metabolic needs or a defence response is only possible by the existence of regulatory mechanisms. These are mostly responsible for an adaptation of the diameter of blood vessels together with the action of the heart to the organism requirements. There are many behavioural and physical factors that have got impact on regulatory circulation of blood in humans. Temperature is one of them. Smooth muscles are those agents that immediately respond to temperature changes what in result changes a tension of blood vessels and so its pressure together with a speed of blood flow. Their contraction increases the blood pressure and pulse rate, where a relaxation reduces it. A terminal that regulates a vascular tension, so called vasomotor centre is located in the medulla (Wisniewski, 1997). By a direct and smooth cooperation, these regulators are able to provide precise response and keep the body temperature within its ranks. Humans as warm-blooded organisms adapted to changes in temperature by moderating amount of heat produced by the body and the amount of heat dissipated. Moreover, a heat flow control is closely connected with changes of skin perfusion as well. Whenever there is a need of heat loss reduction, thus the external temperature decreases, the flow of blood to the surface layers of the skin and thermal conductivity become limited. A body shell change into pale in colour. Blood vessels inside the body narrow, in consequence blood pressure together with pulse achieves a higher rate. This dependency process between the muscular wall contractions together with the compression of blood vessels caused by exposure to the severe cold is known as vasoconstriction (Figure 1).
Figure 1. Vasoconstriction of blood vessels accessed from Anon (2011).
Insulation in the form of subcutaneous fat or some other structures such as hairs can slow down the course of the reaction but it is not able to stop it completely. It needs to be also highlighted that the organism response to the cold water compared with the response to the cold air is much stronger. A thermal conductivity of water is almost thirty times higher than the conductivity of an air, hence the heat loss and blood pressure rate are more rapid what in consequence can lead to very serious disorders (Parsons, 2003). Interaction with cold stress commonly produces gradual and severe discomforts. Together with progressing time a...