Senses

The sense organs are specialized peripheral education, providing the perception of acting on the body external stimuli. Due to its high specialized excitability certain senses provide the perception of only certain types of irritation. In this regard the person allocate organs: sight, hearing, smell, taste, and touch. Do not confuse the concept of "authority feelings" and "receptor", which operates a stimulus. So, for example, should not be confused eyes as the eye and the retina of the eye - receptor, which is part of the senses, but is only one of its components. In addition to the retina, the eye (eye) includes and refraction of the eye, and various of its shell, and its muscular system. Thus, the concept of the senses applies to absolutely certain peripheral education. However, it should be stressed that the concept of the senses is largely conditional, as by itself the senses can provide feel as such. For occurrence of one or other subjective feelings you want the excitement caused in the receptors, received from them in the Central nervous system - in special departments of a bark of the big hemispheres. It is the activities of the higher parts of the brain related to the emergence of subjective sensations. Thus, any of the senses is merely peripheral Department of complex compounds of nervous structures providing the occurrence of specific forms of sensation (see Analyzers).

The sense organs are specialized receptor education, responsible for the perception of the body changes occurring in the world and in the body. The biological purpose of the sense organs is their participation in complex adaptive functioning of the body, aimed at constant balancing it with the medium (I. P. Pavlov). Along with this O. o'clock, being a machine perception of the external world, take part in creating the subjective world of the body, which is a reflection of the external, objective reality.
As the evolutionary development of this aspect of their functions is becoming increasingly important, opening the body ample opportunity to cognize the outside world.
0. hours are analyzers (see) chemical, mechanical, light, sound, temperature and other skin irritations, falling on receptors (see), characterized by thin specialization. So, a part of the visual receptors - sticks - for the twilight of view, and the other part of them - cones - for daylight vision; mechanoreceptors are divided into phase, perceiving dynamic and static, perceiving static deformation, etc.,
A distinctive feature of O. o'clock is their high sensitivity (see) and the ability to function in a wide range of intensities applicable adequate stimuli.
The main regularities of the activity of the senses were established by measurements of the sensations of a man with the help of the so-called psycho-physical method. One of these patterns described in the 19th century, was called the law of Weber-Fechner, according to which the value of experience (S) is proportional to the logarithm of the intensity of the current annoyance (J): S=algJ.
This law, confirmed in further and objective methods of investigation, is common to the various O. o'clock and observed mainly in the field ranges medium intensity irritation.
Not all reactions O. o'clock achieve consciousness in the form of sensations. Reaction occurring in the internal organs, muscles, vestibular apparatus, etc. remain in the form of "dark feelings" (I. M. Sechenov). To study these reactions were widely spread electrophysiological method, which allowed to study bioelectrical phenomena (see) receptors, single fibers and individual nerve cells. Implantation of microelectrodes allowed to study the reactions of the nervous centers and cells to whole animal in combination with emotional and behavioral acts. The success of Cybernetics and bionics has opened the possibility to simulate the function of receptors and neurons and create a prosthesis, offsetting to some extent the lack of some senses. A great role in the objective study of Acting including humans and animals, especially in comparative physiology plan, still plays a method of conditioned reflexes (see).
In response to adequate stimulus receptor particular O. o'clock comes into a state of agitation, which is based on slow the negative change of the charge (depolarization) receptor membrane, called a receptor, or generating capacity. The magnitude of this potential is subject to the law of Weber - Fechner. The receptor potential determines the appearance in the exhaust from the receptor nerve fibers impulses, frequency of which a linear relationship with the amplitude of potential. The increased intensity of irritation leads to an increase in the frequency of impulses in nerve fiber and involvement in the activity of a greater number of fibers. Feeling is determined not simple frequency ID, and the set of impulses in many nerve fibers that transmit information.
From the point of view of modern science specificity perceptions depend on the organization of cortical projections (see the Architectonics of the brain cortex). So, electrical stimulation of the cerebral cortex, carried out during neurosurgical interventions, causes operated a sense, the quality of which depends on the irritation. The application of electrodes to the visual projection causes the feeling of light, to taste - taste, etc. the Specific sensitivity senses to certain stimuli depends on the device receptors. The mechanism of transmission of information from the receptors to the brain is common to all Acting PM and is expressed in the flow pulses with different frequency, duration and myimpulse intervals.
Primary processing of incoming information is already on the periphery. This is because the receptors of each sense organ anatomically linked together to form receptive field, innerved individual nerve fiber. Already in separate receptor can happen a complex interaction of excitation and inhibition, carried out with the participation of intermediate neurons, connected through collaterals to the nerve fibers extending from the receptor. Discharge impulses in any fiber, moreover, depends not only on the parameters of irritation this receptor units, but also on the spatial-temporal distribution of excitation across the group of interacting receptors. In the peripheral interactions highlights the spatial and temporal contrasts stimulus. Spatial summation of excitation defines the value of the square of irritation to characterize the magnitude and reaction threshold O. o'clock For visual apparatus, this dependence is expressed by the formula: J·S=K, where J - threshold intensity, S - area, a constant value. Given that this area is not all the receptor elements can respond, then the formula becomes: J·S(P-p)=K, where P-R-the number of functioning elements (P., Snakin).


In senses allocate touch units that different answer to the effect of the stimulus: some respond to the start (enable) irritation, others on his end (off), the third - at the beginning and the end, the fourth is characterised by continuous impulses, the fifth hampered by the effects of the stimulus. Such specialization, and the existence of elements with different thresholds of sensitivity provide a kind of "filtering" irritation and promote a more subtle analysis of the external world.
A characteristic feature of O. o'clock - functional mobility, i.e. the ability to react not with the whole mass of the constituent elements, and fractional partial. This property is one of the mechanisms of establishing the optimum functioning of O. o'clock (P., Snakin).
When irritants (such as light or sound) is a decrease in the sensitivity of the senses; on the termination of their action or in their absence (darkness, silence) there is a reverse process of increasing the sensitivity of O. o'clock Change sensitivity O. o'clock under the influence of irritation is called adaptation (see). It depends on changes in inflow of afferent impulses from receptors, and from the changes of the functional state of the overlying nervous structures.
Afferent impulses from receptors come in cortical representation O. including both specific and non-specific routes; the latter are connected with reticular formation (see) of the brain. In the cerebral cortex (see) senses presents initial projections, or cores (visual, taste, hearing and other), and areas of overlaps cortical projections which receives impulses from different O. o'clock Most of cortical neurons respond to the arrival of pulses of a certain modality (taste, mechanical, thermal); only a small number of neurons capable of responding to the impulses of different modalities. The presence of areas of overlap cortical projections is one of the mechanisms of interaction O. o'clock, integrate and synthesize information from different receptors. Sense organs do not function in isolation but make braking or aguirutee impact on each other. The versatility of objects and phenomena of the outer world reflects the complex work of O. o'clock the underlying subject matter of perception.
The functioning of O. o'clock is not limited to the receipt of afferent impulses from receptors and their interpretation of the code in the nerve centers of the brain, and also includes the return of the impact of the centres on the receiving device. These reflex by nature influence the nature of the "settings" receptor apparatus for the best perception of irritation and can be performed through special efferent fibres, members of the sensory nerve fibers of the autonomic nervous system, neurohumoral through and through muscular apparatus reception. A great role in regulation of receptors and neurons cortical projections O. o'clock plays the reticular formation. Considerable importance is also conditioned reflex regulation of the senses. Central regulation of sensory input is the basis of the cost of neural structures that in a basis of formation of the mechanism of temporary communications, has the task of switching attention, recognition, and so on, See. also, Taste, Sight, Smell, Touch, Hearing.