How our senses?

From all the above, in previous conversations clearly, what enormous importance perceiving the instruments of our body. On the one hand, through which the external world affects the Central nervous system, changing the work of the various bodies. Without irritation of receptors no reflex. On the other hand, all the wealth of the psyche is due to come through the senses signals from the outside world and from the depths of the body. Hence, the higher manifestations of communication with the environment is impossible without senses, finely analyzing external and internal environment, and therefore called Pavlov analyzers.
We noted already infidelity common domestic perceptions we have all 5 senses. Because one skin of not less than four! However, with some clarification figure 5, you can still leave if, first, not to speak about the kinds of sensitivity, namely about the sense organs (skin, tongue, nose, ear, eye), second, to stress that this is only the outward senses. Besides them there and countless nerve devices, permeating all tissues of the body and sends signals to the brain about the state of our domestic economy. Receptors these are not collected as separate bodies, and therefore against domestic sensitive devices can speak only about the kinds of sensitivity. From a scientific point of view it is more properly, and when considering the external senses, since proper understanding of the body is important, first of all, what kind of irritation, i.e. what changes in the environment (chemical, physical, and so on), are perceived by the nervous system. Therefore, considering the individual sensitive devices - first, outer, inner, - we are going to talk about the kinds of sensitivity, not about the senses.
We will point out once again that the task of perceiving devices includes alarm is not so much about a particular state of the external environment, but it is on its updates. In other words, the analyzers are designed to provide it with information, i.e. new information. In this regard, in the course of evolution, have developed the most interesting property of the most sensitive devices called adaptation (from lat. adaptacio fixture, addiction). Each of us countless times experienced this property senses themselves. So, when entering into the river water seems very cold, and in a few tens of seconds the temperature of its becoming indifferent; it is not impress neither warm nor cold. Same thing when immersed in a tub of hot water. At first the water burns, but very soon we cease to feel it. Often, being in a stuffy atmosphere, we do not feel ipertesti air, although included in the room needs to immediately open the window. Of course, inveterate smokers smell in General is much lower, but in this case the reason is it is adaptation.
It is not necessary, however, to think that we adapt to any irritations. If irritation strong so, can harm the organism, adaptation does not occur. We know, for example, that on the hard floor have difficulty sleeping: pain from the pressure of hard bed on sensitive parts of the body is not reduced, but often, on the contrary, grows. Not only the strength of the stimulus cancels adaptation. There is a kind of sensitivity, which has no rights to this property, muscular sense. Signals from our muscles, alert the brain about their level of voltage included in the feedback necessary to maintain posture. If it came adaptation, would change the severity and frequency of impulses to the muscles; therefore, this type receptors and their Central recipients always on the alert.
Having got acquainted with the basic properties sensitive devices, we now turn to a more detailed consideration of certain types of external sensitivity.