HUMAN ANALYZERS

Changes in environmental conditions and the state of the internal environment of a person are perceived by the nervous system that regulates life processes.

The nervous system includes central nervous system (PNS),

The connection of a person with the environment is carried out with the help of sensory systems or analyzers that perceive and transmit information to the cerebral cortex.

The analyzer consists of a receptor, pathways and a brain ending.

In modern physiology, eight analyzers are distinguished - motor, visual,

auditory, gustatory, olfactory, cutaneous, vestibular and visceral.

However, in the system of human interaction with environmental objects, the main ones when a danger is detected are visual, auditory and skin analyzers.

Others perform an auxiliary or complementary function. However, it must be taken into account that there are a number of dangerous factors(ionizing radiation, electromagnetic fields, ultrasound, infrared radiation), which have an important biological effect on human body, but there are no corresponding natural analyzers for their perception.

HUMAN ANALYZERS

The nervous system includes central nervous system(CNS), which includes the spinal cord and brain and peripheral nervous system(PNS),

consisting of nerve fibers and nodes.

The analyzer consists of receptor pathways (PP) and brain endings (MO).

The receptor receives information that is encoded in nerve impulses and is transmitted along the pathways through the brain ending to analyzer core(I).

Human reaction and decision-making is in the nature of an unconditioned (BR) or conditioned (UR) reflex.

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VISUAL ANALYZER

An exceptional role in a person's life and his relationship with the outside world is played by visual analyzer. With its help, we get the lion's share (about 90%) of information. Through vision, we almost instantly learn the shape, size, color of an object, determine the direction and distance to it.

The visual analyzer includes the eye, optic nerve and visual center located in occipital lobe of the cerebral cortex.

The eye is a complex optical system, where the limiter luminous flux, carrying information, is the pupil. Depending on the brightness of the light, its size changes.

Having entered the eye through the pupil, light rays, refracted on the surface of the eyeball, in the cornea, lens and vitreous body, converge on the retina, giving an image of a visible object on it.

The retina lines the posterior half of the eyeball and is composed of

light-sensitive receptors - rods of cones.

Cones and rods perform different functions. Cones allow you to clearly distinguish fine details and color of objects, but they require good illumination for this, and therefore provide the so-called "daytime" vision. "Night" vision is carried out with the help of retinal rods, which are able to respond to low light, but do not allow to distinguish fine details and color.

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VISUAL ANALYZER

The human eye transforms energy optical radiation in visual sensation.

The visible part of the optical part of the spectrum of electromagnetic oscillations with a wavelength of 380 - 780 nm is perceived. Eye directly responds to

brightness and selective spectral composition incident radiation flux.

visibility curve.

The relative spectral sensitivity of the eye Kλ is equal to

the ratio of the sensitivity of the eye to homogeneous radiation with a wavelength λ (qλ) to its maximum value for radiation with a wavelength of 555 nm(qmax ) for yellow-green radiation.

Is yellow-green

radiation.

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VISUAL ANALYZER

Radiant fluxes equal in light power, differing from each other in the wavelength of radiation (color), cause radiation unequal in intensity in the eye, which is characterized by visibility curve.

As you approach the boundaries of the visible spectrum, the sensitivity of the eye decreases, and most visible in daylight is yellow-green

radiation.

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VISUAL ANALYZER

Visual acuity. When assessing the perception of spatial characteristics, the main concept is visual acuity, which characterized by the minimum angle at which two points are seen as separate.

Visual acuity depends on illumination, contrast, shape of the object and other factors.

With increasing illumination, visual acuity increases. With a decrease in contrast, visual acuity decreases. Visual acuity also depends on the location of the image projection on the retina.

Vision inertia. The sensation caused by a light signal persists for a certain time, despite the disappearance of the signal or a change in its characteristics, for 0.1 - 0.2 s.

The frequency at which the flickering disappears is called critical flicker fusion frequency. When flickering light is used as a signal, the optimal frequency is within 3-10 Hz. The inertia of vision, in addition, causes stroboscopic effect.

In this case, for example, the illusion of immobility (deceleration of movement) arises, which occurs when a moving object periodically takes its previous position.

Particularly when illuminated by pulsed light, rotating parts of the equipment may appear to be stationary, which is dangerous to humans.

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VISUAL ANALYZER

Line of sight. When perceiving objects in two-dimensional and three-dimensional space, a distinction is made between the field of view and depth vision.

The binocular field of view covers 120-160° horizontally, 55-60° vertically and 65-72° downwards.

With the perception of color, the size of the field of view decreases. The zone of optimal visibility is limited by the field: up - 25 °, down - 35 °, to the right and left by 32 °.

Depth of vision provides spatial perception. Thus, the error in estimating the absolute distance at a distance of up to 30 m averages 12% of the total distance.

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HEARING ANALYZER

auditory system human includes

outer, middle and inner ear, auditory nerve and central auditory pathways.

fluctuations eardrum are transmitted to the inner ear, where the sound acts on sensitive nerve endings, each of which responds to vibrations of a certain frequency.

Mechanical vibrations are converted in the organ of hearing into electrical potentials.

The main parameters of sound waves are the intensity and frequency of oscillations, which are subjectively perceived in auditory sensations as

loudness and pitch.

Sound audibility zone is limited in intensity hearing threshold and

pain threshold.

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HEARING ANALYZER

In terms of frequency, the region of auditory sensations lies from 16 Hz to 20 kHz.

The sound audibility zone is limited by two curves: hearing threshold(1)

and pain threshold (2).

hearing threshold(1 ), in contrast to the threshold pain sensation(2 ), strongly depends on the frequency. The sound level L at the threshold of hearing is 0 dB at a sound pressure P of 2 * 10-5 Pa, and at the threshold of pain 140 dB at a sound pressure of 2 * 102 Pa.

The area between the thresholds is called the sound audibility zone.

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HEARING ANALYZER

Equal Loudness Curves

The absolute differential threshold for distinguishing frequencies is ~2-3 Hz.

The relative differential threshold is almost constant and is equal to

The maximum sensitivity of the auditory analyzer lies in the frequency range of 3...5 kHz.

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An analyzer is a system that provides perception, delivery to the brain and analysis of any type of information in it (visual, auditory, olfactory, etc.). Each analyzer of the sense organs consists of a peripheral section (receptors), a conductive section (nerve pathways) and a central section (centers that analyze this type of information).

More than 90% of information about the world around a person receives through vision.

The organ of vision of the eye consists of the eyeball and an auxiliary apparatus. The latter include eyelids, eyelashes, muscles of the eyeball and lacrimal glands. The eyelids are folds of skin lined from the inside with a mucous membrane. Tears formed in the lacrimal glands wash the anterior part of the eyeball and pass through the nasolacrimal canal into the oral cavity. An adult should produce at least 3-5 ml of tears per day, which perform a bactericidal and moisturizing role.

The eyeball has a spherical shape and is located in the orbit. With the help of smooth muscles, it can rotate in the orbit. The eyeball has three shells. The outer - fibrous, or albuminous - shell in front of the eyeball passes into a transparent cornea, and its posterior section is called the sclera. Through the middle shell - the vascular - the eyeball is supplied with blood. Ahead in the choroid there is a hole - the pupil, allowing light rays to enter the inside of the eyeball. Around the pupil, part of the choroid is colored and is called the iris. The cells of the iris contain only one pigment, and if it is small, the iris is colored blue or gray, and if there is a lot, brown or black. The muscles of the pupil dilate or constrict it, depending on the brightness of the light illuminating the eye, from approximately 2 to 8 mm in diameter. Between the cornea and the iris is the anterior chamber of the eye, filled with fluid.

Behind the iris is a transparent lens - a biconvex lens necessary for focusing light rays on the inner surface of the eyeball. The lens is equipped with special muscles that change its curvature. This process is called accommodation. Between the iris and the lens is the posterior chamber of the eye.

Most of the eyeball is filled with a transparent vitreous body. After passing through the lens and the vitreous body, the rays of light fall on the inner shell of the eyeball - the retina. This is a multilayer formation, and its three layers, facing inside the eyeball, contain visual receptors - cones (about 7 million) and rods (about 130 million). The rods contain the visual pigment rhodopsin, they are more sensitive than cones and provide black and white vision in low light. Cones contain the visual pigment iodopsin and provide color vision in good light conditions. It is believed that there are three types of cones that perceive red, green and purple and accordingly. All other shades are determined by a combination of excitations in these three types of receptors. Under the action of light quanta, visual pigments are destroyed, generating electrical signals that are transmitted from rods and cones to the ganglionic layer of the retina. The processes of the cells of this layer form the optic nerve, which exits the eyeball through the blind spot - a place where there are no visual receptors.

Most of the cones are located directly opposite the pupil - in the so-called yellow spot, and in the peripheral parts of the retina there are almost no cones, only rods are located there.

After leaving the eyeball, the optic nerve follows the superior tubercles of the quadrigemina of the midbrain, where visual information undergoes primary processing. Along the axons of the neurons of the superior tubercles, visual information enters the lateral geniculate bodies of the thalamus, and from there to the occipital lobes of the cerebral cortex. It is there that the visual image that we subjectively feel is formed.

It should be noted that the optical system of the eye forms on the retina not only a reduced, but also an inverted image of an object. Signal processing in the central nervous system occurs in such a way that objects are perceived in a natural position.

The human visual analyzer has amazing sensitivity. So, we can distinguish a hole in the wall with a diameter of only 0.003 mm illuminated from the inside. AT ideal conditions(air purity, calmness) the fire of a match lit on the mountain can be discerned at a distance of 80 km. A trained person (and women do it much better) can distinguish hundreds of thousands of color shades. The visual analyzer only needs 0.05 seconds to recognize an object that has fallen into the field of view.

auditory analyzer

Hearing is necessary for the perception of sound vibrations in a fairly wide range of frequencies. In adolescence, a person distinguishes sounds in the range from 16 to 20,000 hertz, but by the age of 35, the upper limit of audible frequencies drops to 15,000 hertz. In addition to creating an objective holistic picture of the surrounding world, hearing provides verbal communication of people.

The auditory analyzer includes the organ of hearing, the auditory nerve and brain centers that analyze auditory information. The peripheral part of the organ of hearing, that is, the organ of hearing, consists of the outer, middle and inner ear.

The outer ear of a person is represented by the auricle, external auditory canal and tympanic membrane.

The auricle is a cartilaginous formation covered with skin. In humans, unlike many animals, the auricles are practically motionless. The external auditory meatus is a canal 3-3.5 cm long, ending with a tympanic membrane that separates the outer ear from the middle ear cavity. The latter, which has a volume of about 1 cm3, contains the smallest bones of the human body: the hammer, anvil and stirrup. The hammer "handle" fuses with the eardrum, and the "head" is movably attached to the anvil, which is movably connected to the stirrup with its other part. The stirrup, in turn, with a wide base is fused with the membrane of the oval window leading to the inner ear. The middle ear cavity is connected to the nasopharynx through the Eustachian tube. This is necessary to equalize the pressure on both sides of the eardrum with changes in atmospheric pressure.

The inner ear is located in the cavity of the pyramid of the temporal bone. The organ of hearing in the inner ear is the cochlea - a bony, spirally twisted canal with 2.75 turns. Outside, the cochlea is washed by perilymph, which fills the cavity of the inner ear. In the canal of the cochlea there is a membranous bone labyrinth filled with endolymph; in this labyrinth there is a sound-receiving apparatus - a spiral organ, consisting of a main membrane with receptor cells and an integumentary membrane. The main membrane is a thin membranous septum that separates the cochlear cavity and consists of numerous fibers of various lengths. About 25 thousand receptor hair cells are located in this membrane. One end of each receptor cell is fixed to a main membrane fiber. It is from this end that the fiber of the auditory nerve departs. When a sound signal is received, the air column filling the external auditory meatus oscillates. These vibrations are picked up by the tympanic membrane and transmitted through the hammer, anvil and stirrup to the oval window. When passing through the sound ossicle system sound vibrations increase approximately 40-50 times and are transmitted to the perilymph and endolymph of the inner ear. Through these fluids, vibrations are perceived by the fibers of the main membrane, and high sounds cause oscillations of shorter fibers, and low ones - longer ones. As a result of fluctuations in the fibers of the main membrane, receptor hair cells are excited, and the signal is transmitted along the fibers of the auditory nerve first to the nuclei of the inferior colliculus of the quadrigemina, from there to the medial geniculate bodies of the thalamus and, finally, to the temporal lobes of the cerebral cortex, where the highest center of auditory sensitivity is located.

The vestibular analyzer performs the function of regulating the position of the body and its individual parts in space.

The peripheral part of this analyzer is represented by receptors located in the inner ear, as well as large quantity receptors located in muscle tendons.

In the vestibule of the inner ear there are two sacs - round and oval, which are filled with endolymph. In the walls of the sacs there are a large number of receptor hair-like cells. In the cavity of the sacs are otoliths - crystals of calcium salts.

In addition, in the cavity of the inner ear there are three semicircular canals located in mutually perpendicular planes. They are filled with endolymph, receptors are located in the walls of their extensions.

With a change in the position of the head or the whole body in space, the otoliths and endolymph of the semicircular tubules move, exciting the hair-like cells. Their processes form the vestibular nerve, through which information about a change in the position of the body in space enters the nuclei of the midbrain, the cerebellum, the nuclei of the thalamus, and, finally, to the parietal region of the cerebral cortex.

Tactile Analyzer

Touch is a complex of sensations that occurs when several types of skin receptors are irritated. Touch receptors (tactile) are of several types: some of them are very sensitive and are excited when the skin on the hand is pressed by only 0.1 microns, others are excited only with significant pressure. On average, there are about 25 tactile receptors per 1 cm2, but there are much more of them on the skin of the face, fingers, and tongue. In addition, the hairs that cover 95% of our body are sensitive to touch. At the base of each hair is a tactile receptor. Information from all these receptors is collected in the spinal cord and, along the conducting paths of the white matter, enters the nuclei of the thalamus, and from there to the highest center of tactile sensitivity - the region of the posterior central gyrus of the cerebral cortex.

Taste Analyzer

Peripheral part of the taste analyzer - taste buds located in the epithelium of the tongue and, to a lesser extent, the mucosa oral cavity and throats. Taste buds react only to substances dissolved in water, and insoluble substances have no taste. A person distinguishes four types of taste sensations: salty, sour, bitter, sweet. Most of the receptors for sour and salty are located on the sides of the tongue, for sweet - at the tip of the tongue, and for bitter - on the root of the tongue, although a small number of receptors for any of these stimuli are scattered throughout the mucous membrane of the entire surface of the tongue. The optimal value of taste sensations is observed at a temperature in the oral cavity of 29°C.

From the receptors, information about taste stimuli through the fibers of the glossopharyngeal and partially facial and vagus nerves enters the midbrain, the nuclei of the thalamus and, finally, to the inner surface of the temporal lobes of the cerebral cortex, where the higher centers of the taste analyzer are located.

Olfactory analyzer

The sense of smell provides perception of various smells. Olfactory receptors are located in the mucous membrane of the upper part of the nasal cavity. total area, occupied by olfactory receptors, is 3-5 cm2 in humans. For comparison: in a dog this area is about 65 cm2, and in a shark it is 130 cm2. The sensitivity of the olfactory vesicles, which terminate the olfactory receptor cells in humans, is also not very high: to excite one receptor, it is necessary that 8 molecules of an odorous substance act on it, and the sensation of smell arises in our brain only when about 40 receptors are excited. Thus, a person subjectively begins to smell a smell only when more than 300 molecules of an odorous substance enter the nose. Information from the olfactory receptors along the fibers of the olfactory nerve enters the olfactory zone of the cerebral cortex, located on the inner surface of the temporal lobes.

Human analyzers (sight, hearing, smell, taste, touch)

Analyzer is a term introduced by I.P. Pavlov to designate a functional unit responsible for receiving and analyzing sensory information of any one modality.

Set of neurons different levels hierarchies involved in the perception of stimuli, the conduction of excitation, and in the analysis of stimulus.

The analyzer, together with a set of specialized structures (sense organs) that contribute to the perception of environmental information, is called a sensory system.

For example, the auditory system is a collection of very complex interacting structures, including the outer, middle, inner ear and a collection of neurons called the analyzer.

Often the terms "analyzer" and "sensor system" are used as synonyms.

Analyzers, like sensory systems, classify according to the quality (modality) of those sensations in the formation of which they participate. These are visual, auditory, vestibular, gustatory, olfactory, skin, vestibular, motor analyzers, analyzers of internal organs, somatosensory analyzers.

The analyzer is divided into three sections:

1. Perceiving organ or receptor designed to convert the energy of irritation into the process of nervous excitation;

2. Conductor, consisting of afferent nerves and pathways, through which impulses are transmitted to the overlying parts of the central nervous system;

3. The central section, consisting of relay subcortical nuclei and projection sections of the cerebral cortex.

In addition to the ascending (afferent) pathways, there are descending fibers (efferent), along which the regulation of the activity of the lower levels of the analyzer from its higher, especially cortical, departments is carried out.

Analyzers are special structures of the body that serve to enter external information into the brain for its subsequent processing.

Minor terms

• receptors;

Block diagram of terms

In the process of labor activity, the human body adapts to environmental changes due to the regulatory function of the central nervous system (CNS). The individual is connected to the environment through analyzers, which consist of receptors, nerve pathways and a brain end in the cerebral cortex. The brain end consists of a nucleus and elements scattered throughout the cerebral cortex, providing nerve connections between individual analyzers. For example, when a person eats, he feels the taste, smell of food and feels its temperature.

If the stimulus causes pain or disruption of the analyzer, this will be the upper absolute threshold of sensitivity. The interval from minimum to maximum determines the sensitivity range (for sound from 20 Hz to 20 kHz).

In humans, receptors are tuned to the following stimuli:

· electromagnetic oscillations light range - photoreceptors in the retina;

mechanical vibrations of air - phonoreceptors of the ear;

changes in hydrostatic and osmotic blood pressure - baro- and osmoreceptors;

Change in body position relative to the vector of gravity - receptors of the vestibular apparatus.

In addition, there are chemoreceptors (responding to exposure to chemical substances), thermoreceptors (perceive temperature changes both inside the body and in the environment), tactile receptors and pain receptors.

In response to changes in environmental conditions, so that external stimuli do not cause damage and death of the body, compensatory reactions are formed in it, which can be: behavioral (change of location, withdrawal of the hand from hot or cold) or internal (change in the mechanism of thermoregulation in response to change in microclimate parameters).

A person has a number of important specialized peripheral formations - sensory organs that ensure the perception of external stimuli affecting the body. These include the organs of sight, hearing, smell, taste, touch.

Do not confuse the concepts of "sense organs" and "receptor". For example, the eye is the organ of vision, and the retina is the photoreceptor, one of the components of the organ of vision. The sense organs alone cannot provide sensation. For the occurrence of a subjective sensation, it is necessary that the excitation that has arisen in the receptors enters the corresponding section of the cerebral cortex.

visual analyzer includes the eye, optic nerve, visual center in the occipital part of the cerebral cortex. The eye is sensitive to the visible spectrum electromagnetic waves from 0.38 to 0.77 µm. Within these limits, different wavelength ranges cause different sensations (colors) when exposed to the retina:

The adaptation of the eye to the distinction of a given object under given conditions is carried out by three processes without the participation of the human will.

Accommodation- changing the curvature of the lens so that the image of the object is in the plane of the retina (focusing).

Convergence- rotation of the axes of vision of both eyes so that they intersect at the object of difference.

Adaptation- adaptation of the eye to a given level of brightness. During the period of adaptation, the eye works with reduced efficiency, so it is necessary to avoid frequent and deep re-adaptation.

Hearing- the ability of the body to receive and distinguish sound vibrations with an auditory analyzer in the range from 16 to 20,000 Hz.

Smell- the ability to perceive odors. The receptors are located in the mucous membrane of the upper and middle nasal passages.

Man possesses varying degrees sense of smell to various odorous substances. Pleasant odors improve a person's well-being, while unpleasant ones act depressingly, cause negative reactions up to nausea, vomiting, fainting (hydrogen sulfide, gasoline), can change skin temperature, cause disgust for food, lead to depression and irritability.

Taste- a sensation that occurs when certain water-soluble chemicals are exposed to taste buds located on different parts of the tongue.

Taste is made up of four simple taste sensations: sour, salty, sweet, and bitter.

Functions and types of human analyzers (Table)

All other flavor variations are combinations of basic sensations. Various plots tongues have different sensitivity to taste substances: the tip of the tongue is sensitive to sweet, the edges of the tongue - to sour, the tip and edge of the tongue - to salty, the root of the tongue - to bitter. The mechanism of perception of taste sensations is associated with chemical reactions. It is assumed that each receptor contains highly sensitive protein substances that decompose when exposed to certain flavoring substances.

Touch- a complex sensation that occurs when the receptors of the skin, the outer parts of the mucous membranes and the muscular-articular apparatus are irritated.

The skin analyzer perceives external mechanical, temperature, chemical and other skin irritants.

One of the main functions of the skin is protection. Sprains, bruises, pressures are neutralized by an elastic fatty lining and elasticity of the skin. The stratum corneum protects the deep layers of the skin from drying out and is highly resistant to various chemicals. The melanin pigment protects the skin from UV rays. The intact layer of skin is impervious to infections, while sebum and sweat create a deadly acidic environment for germs.

An important protective function of the skin is participation in thermoregulation. 80% of all body heat transfer is carried out by the skin. At high ambient temperatures, skin vessels expand and heat transfer by convection increases. At low temperatures, the vessels narrow, the skin turns pale, and heat transfer decreases. Heat is also transferred through the skin by sweating.

Secretory function is carried out through the sebaceous and sweat glands. With sebum and sweat, iodine, bromine, and toxic substances are released.

The metabolic function of the skin is participation in the regulation of the general metabolism in the body (water, mineral).

The receptor function of the skin is perception from the outside and transmission of signals to the central nervous system.

Types of skin sensitivity: tactile, pain, temperature.

With the help of analyzers, a person receives information about outside world, which determines the work of the functional systems of the body and human behavior.

The maximum transmission rates of information received by a person with the help of various sense organs are given in Table. 1.6.1

Table 1. Characteristics of the sense organs

The conduction path of the visual vestibular analyzer

Lecture 5. Analyzers

Analyzers are neuro-sensory organs that are able to register impulses in the central part of the analyzer. For the first time, the concept of analyzers was introduced by Semenov, and he singled out 3 components of their structures in analyzers:

receptor part (heat, cold)

conducting part (auditory nerve, optic)

the central part, which is represented by a certain zone of the cerebral cortex.

In humans, visual and auditory analyzers are distinguished, in addition, vestibular, olfactory and tactile analyzers.

visual analyzer.

This is a neuro-sensory organ that is capable of registering electromagnetic rays in the visible part of the spectrum. The rays below the perception zone are called infrared, above - UV.

The receptor part of the analyzer is the retinal receptors, because sticks and cones. The conducting part is the optic nerves, which form the chiasm at the level of the midbrain. The central part is the perceiving areas of the cerebral cortex (occipital lobes).

Organ of vision.

A person is characterized by a paired organ of vision - the eyes, which lie in the orbit. The eyes are attached to the walls of the orbit by 3 pairs of oculomotor muscles. Eyes are protected by eyebrows, eyelashes, eyelids. In the upper part of the orbit above the eye is the lacrimal gland. Its secret - tears - moisten the surface of the eye, prevent it from drying out, and also contain bactericidal substances, such as lysocin, which prevents the development of bacteria on the mucous membrane. Partially, tears enter the nasal cavity through the duct.

The eye is surrounded by membranes, and the outermost shell of the eye - the albuginea, or sclera, on the front side passes into a thicker and more transparent cornea. In addition, the sclera connects with the mucous lining of the eyelid, forming the conjunctiva, which holds the eye in the orbit, and, in addition, protects the cornea from external influences.

The more inner shell of the eye is the choroid, which contains the capillaries of the circulatory system, because. they are absent in the retina itself, i.e. the main function of the choroid is trophic.

The innermost part of the choroid is the pigment layer, where the pigments are located: fuscin and melanin. The outer segments of the rod and cone receptors are immersed in the pigment layer, so the main function of the pigment layer is to hold the rays and excite the receptors. On the front side of the eye, the choroid and the pigment layer pass into the iris, and this membrane is discontinuous and the break in it is called the pupil.

The pupil aperture can constantly change depending on the lighting. The diaphragm of the pupil changes depending on the contraction of the annular and radial muscle fibers, which are innervated by the parasympathetic system.

The innermost shell of the eye - the retina - contains receptors: rods and cones. The concentration of receptors is not the same in different parts of the eye: rods predominate on the periphery of the eye, cones - in the center of the eye, especially in the region of the so-called central fossa. Here a yellow spot is formed, i.e. the maximum concentration of cones, and here colors are most well perceived. The receptors are braided with neurons, the axons of which, gathering together, form the optic nerve.

The exit point of the optic nerve is called the blind spot.

The refractive optical structures of the eye include:

cornea

aqueous humor that fills the chambers of the eye

lens

vitreous,

and the refractive power is measured in diopters.

On the retina of each eye, due to the refractive power of the media, primarily the lens, a real, inverse and reduced image is built. A person sees in direct form thanks to the daily training of the visual analyzer and indicators from other analyzers.

The optical setting of the eye on an object that moves relative to the eye is called accommodation, and the rays reflected from the object in the norm should converge to a focus point on the retina. Accommodation is achieved by changing the refractive power of the lens. For example, if an object is close to the eyes, the ciliary muscle contracts, the zinn ligaments relax, the lens takes the form of a cylinder, its refractive power is maximum, and the rays converge to a focal point on the retina. If the object is far from the retina, the ciliary muscle relaxes, the ligaments of zinn are stretched, the lens takes a flat shape, its refractive power is minimal, and the rays converge to a focal point on the retina. It is believed that the nearest point of clear vision is located on such minimum distance from the eyes, when the 2 nearest points of the object are clearly visible.

The far frame of clear vision lies at infinity, but noticeable accommodation is observed only when the distance to the object does not exceed 60 meters. Very good accommodation is observed when the distance to the object becomes 20 meters.

Pathology of accommodation.

Normally, the rays converge to a focal point on the retina.

Myopia – myopia- in this case, the rays converge to a focal point up to the retina.

Causes of myopia:

congenital (the eye is larger than the norm by 2-3 mm)

deterioration of the elasticity of the ligaments, the ciliary muscle is tired and there is a spasm of accommodation.

Help biconcave glass.

farsightedness- in this case, a parallel beam of light is collected at a focal point behind the retina.

Causes:

the length of the eye is less than the norm by 2-3 mm

inelasticity of the ligaments, which is observed with age, therefore, after 40, age-related farsightedness develops.

Help biconvex glass.

Astigmatism- in this case, the curvature of the cornea is increased, and the rays do not converge at all to the focal point. Cylindrical glasses help.

Retina.

The retina of the eye is a collection of receptors (rods and cones), i.e. is the peripheral part of the visual analyzer.

The structure of the retina resembles the structure of a 3-neural network. The outer part of the receptors is immersed in the pigment layer; here, in the pigment layer, are the pigments that hold the light rays. The receptors are connected to a layer of bipolar neurons, and each such neuron is connected to only one receptor. The bipolar neurons are connected to the multipolar, and the axons of the multipolar neurons combine to form the optic nerve. And one multipolar neuron can be connected to several bipolar neurons at once. Between multipolar neurons there is a stellate cell, which connects all receptive fields into a single network.

The human eye of all land animals is inverted. This means that the beam of the set first hits the vitreous body, then the layers of neurons, and only then the receptors. Thus, scattered light reaches the retina and the receptors are not affected. In many marine animals, the eye is not inverted; scattered light hits the receptors directly. Rods and cones contain pigments that break down when exposed to light. The rods contain the pigment rhodopsin, the cones contain the pigment iodopsin.

Rhodopsin is able to decompose into retinene pigment and opsin protein under the influence of even a small amount of light. Therefore, rods provide vision at dusk.

There are 3 types of iodapsins and it decomposes under the influence of intense illumination, therefore iodapsins perceive color, and due to 3 types of this pigment, all colors of the visible part of the spectrum are perceived.

The photochemical reaction of the decomposition of rhodopsin causes depolarization of the rod membrane, and this wave of depolarization first covers bipolar neurons, and then multipolar ones. With further exposure to light, the retin pigment turns into vitamin A. The reverse synthesis of rhodopsin occurs both in the light and in the dark, but it goes faster in the dark, therefore, with prolonged exposure to bright light, or when exposed to light reflected from snow, or a lack of vitamin And there is a disease of hemeralopia, or night blindness.

Cone pathologies are associated with pathologies of color perception, tk. cones are responsible for the perception of color, hue and saturation:

partial loss of color perception

color blindness (a person cannot distinguish certain colors spectrum: red=green, yellow=blue)

complete loss of color perception (achromatic vision)

A person is characterized by vision with two eyes, or binocular vision. It allows you to correctly assess the distance to the object, assess the texture, volume, relief, and the rays reflected from one point of the object are able to focus in one place on the retinas of both eyes (identical fixation), or in different places(non-identical commit).

Due to non-identical fixation, a person perceives relief and volume. Impulses along the optic nerves are directed to the centers in the occipital lobes, where the overall picture is formed.

auditory analyzer.

The second leading analyzer in humans. This is a neuro-sensory organ that perceives sound vibrations in a certain range from 16 thousand to 22 thousand kHz. The area below perception is infrasound, above perception is ultrasound.

The auditory analyzer consists of 3 parts:

receptor part. Represented by the mechano-receptors of the inner ear, which form the cortical organ

auditory nerves that form chiasma at the level of the pons

the central part, which includes certain centers in the temporal lobes of the cortex.

Organ of hearing.

Humans have a paired hearing organ, which includes the outer ear, middle ear, and inner ear.

The outer ear is represented by the auricle and auditory meatus. The sink provides directional sound reception. The ear canal is 2.5 cm covered with ciliated epithelium. A secret is produced in epithelial cells, especially in small unicellular glands that synthesize earwax. It performs the function of protection, because. dust settles on it, and, in addition, sulfur contains bactericidal substances that kill bacteria. In addition, the air in the ear canal is warmed and humidified. The ear canal ends with the tympanic membrane, which has a fibrous structure. sound waves the tympanic membrane is struck and the fibers of the membrane begin to vibrate, which causes the ossicles of the middle ear to vibrate.

The middle ear is a cavity filled with air, and to equalize the pressure between the middle ear and the nasopharynx, a connection occurs in the form of the Eustachian tube. The bones in the middle ear are the hammer, anvil, and stirrup. The hammer with its handle is connected to the eardrum, it is in contact with the anvil, and the anvil with the stirrup, and the surface contact area from the eardrum to the stirrup, which is located on the oval window, decreases, and this makes it possible to amplify weak sounds and weaken strong ones. Thus, the middle ear takes part in the transmission of vibrations from the eardrum to the inner ear.

The inner ear is a bony labyrinth in the form of a cochlea, which is twisted 2.5 turns in the temporal bone. The bone labyrinth communicates with the cavity of the middle ear by means of an oval and a round window, which are covered with membrane membranes, and on the membrane of the oval window there is a stirrup bone. Inside the bony labyrinth, a membranous labyrinth passes, represented by 2 membranes: the basement membrane and Reisner's membrane. At the top of the cochlea, the membranes join, but in general, these membranes divide the cochlea into 3 canals, or ladders. The canals of the inner ear are filled with fluid, the cochlear canal is filled with endolymph, and the tympanic canal and vestibule are filled with relymph. These fluids are somewhat different in composition.

The sound wave causes the ossicles of the middle ear to vibrate. Vibrations of the membrane of the oval window are observed, and these vibrations are transmitted to the fluid of the inner ear, and they are damped on the membrane of the round window, with the round window acting as a resonator. The vibrations are transmitted to the basement membrane and endolymph, and are recorded by the organ of Corti located here. The organ of Corti is the receptor part of the analyzer, which is represented by hair-like cells and these cells are located on the main membrane in several rows. These cells are closed by an integumentary membrane, which at one end is attached to the basement membrane at the base of the cochlea, while its other end is free.

Vibrations of the fluid lead to vibrations of the main membrane and to the fact that the integumentary membrane of the organ of Corti begins to irritate the hairs of the mechanoreceptors. The receptor membrane is depolarized, and a wave of depolarization travels along the auditory nerve.

The fibers of the main membrane have different thicknesses and can vibrate with different amplitudes, which ensures the differentiation of high and low sounds.

It is believed that high sounds are perceived at the base of the cochlea, and low sounds are perceived at the top of the cochlea. There are several hypotheses for the perception and frequency analysis of sound:

1. resonance hypothesis. It is believed that at the base of the cochlea, the basement membrane resonates with the sound wave and the integumentary membrane irritates a small group of hair-like cells.
2. burst hypothesis. It is believed that at the top of the cochlea, the integumentary membrane irritates entire receptive fields and a whole volley of impulses is sent to the central nervous system. It is believed that low sounds are perceived in this way.

vestibular apparatus.

vestibular analyzer.

This is a neuro-sensory organ that registers changes in the position of the body or parts of the body relative to each other. The vestibular analyzer consists of 3 parts:

mechano-receptors of the vestibular apparatus

vestibular branch of the auditory nerve

central part in the temporal bone

The vestibular apparatus (c.a) lies in the temporal bone and is associated with the bony labyrinth of the inner ear, although c.a. and the cochlea of ​​the inner ear have completely different origins.

V.a. It is represented by a bony labyrinth filled with fluid, inside which passes a membranous labyrinth, also filled with fluid. The membranous labyrinth forms the organs of the vestibule, which are represented by round and oval sacs and 3 semicircular canals, each canal is associated with a round and oval sac. At one end of the channel is an extension, or ampulla.

The vestibular organs are lined with epithelium and filled with fluid. Among the cells of the epithelium, hair-like cells are located in groups. Above the cells is a gelatinous membrane, into which the hairs of the cells are immersed.

Human analyzers

The membrane contains Ca2+ crystals called otoliths or statocysts. When moving the body or head, the oval and round sacs begin to shift relative to each other, the otoliths begin to shift, which pull the gelatinous membrane behind them and it irritates the hair-like cells.

The vestibular organs perceive the beginning and the end rectilinear motion, rectilinear acceleration, gravity. The semicircular canals perceive rotational movements and angular acceleration, they are filled with liquid, and hair-like cells are found only in ampoules. When the position of the body changes, the liquid filling the ampoules lags behind the walls of the ampule and irritates the hairs.

Taste analyzer.

Taste buds are located in the taste buds, which are formed on the tongue and on the oral mucosa. Impulses from the receptors go to the parietal lobes of the cerebral cortex. It is believed that the tip of the tongue perceives a sweet taste, at the root of the tongue - a bitter taste, on the sides - sour and salty.

Olfactory analyzer.

This is the only analyzer that has no representation in the cortex. Receptors are located in the nasal cavity and are able to perceive volatile compounds. These impulses are analyzed at the level of the ancient cortex, as well as through the limbic system of the brain.

Tactile analyzer.

The receptor part of this analyzer refers to the skin, where pain, heat, cold receptors are located - tactile receptors. These receptors can be free nerve endings, such as pain receptors, as well as encapsulated nerve endings, such as pressure receptors. The sensory nerves of this analyzer form a decussation at the level of the pons, and the central part of the analyzer is located in the parietal lobes of the cortex.

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Analyzers, sense organs and their meaning

Analyzers. All living organisms, including humans, need information about the environment. This possibility is provided to them by sensory (sensitive) systems. The activity of any sensory system begins with perception stimulus energy receptors transformation it into nerve impulses and transmission them through a chain of neurons to the brain, in which nerve impulses converted into specific sensations - visual, olfactory, auditory, etc.

Studying the physiology of sensory systems, academician I.P.

human analyzers. The main sense organs and their functions

Pavlov created the doctrine of analyzers. Analyzers are called complex nervous mechanisms by means of which the nervous system receives irritations from the external environment, as well as from the organs of the body itself and perceives these irritations in the form of sensations. Each analyzer consists of three sections: peripheral, conductive and central.

Peripheral department It is represented by receptors - sensitive nerve endings that have selective sensitivity only to a certain type of stimulus. Receptors are part of the corresponding sense organs. In complex sensory organs (vision, hearing, taste), in addition to receptors, there are also support structures, which provide a better perception of the stimulus, and also perform protective, supporting and other functions. For example, auxiliary structures of the visual analyzer are represented by the eye, and visual receptors are only sensitive cells (rods and cones). Receptors are outdoor, located on the surface of the body and perceiving irritations from the external environment, and internal, which perceive irritations from the internal organs and the internal environment of the body,

conductor department The analyzer is represented by nerve fibers that conduct nerve impulses from the receptor to the central nervous system (for example, the visual, auditory, olfactory nerve, etc.).

Central department analyzer - this is a certain area of ​​the cerebral cortex, where the analysis and synthesis of incoming sensory information and its transformation into a specific sensation (visual, olfactory, etc.) takes place.

A prerequisite for the normal functioning of the analyzer is the integrity of each of its three departments.

visual analyzer

The visual analyzer is a set of structures that perceive light energy in the form electromagnetic radiation with a wavelength of 400 - 700 nm and discrete particles of photons, or quanta, and forming visual sensations. With the help of the eye, 80-90% of all information about the world around us is perceived.

Thanks to the activity of the visual analyzer, the illumination of objects, their color, shape, size, direction of movement, the distance at which they are removed from the eye and from each other are distinguished. All this allows you to evaluate the space, navigate in the world, perform different kinds purposeful activity.

Along with the concept of the visual analyzer, there is the concept of the organ of vision.

The organ of vision it is an eye that includes three functionally different elements:

the eyeball, in which the light-perceiving, light-refracting and light-regulating apparatuses are located;

protective devices, i.e. outer shells of the eye (sclera and cornea), lacrimal apparatus, eyelids, eyelashes, eyebrows;

the motor apparatus, represented by three pairs of eye muscles (external and internal rectus, superior and inferior rectus, superior and inferior oblique), which are innervated by III (oculomotor nerve), IV (trochlear nerve) and VI (abducens nerve) pairs of cranial nerves.

External analyzers

Reception and analysis of information is carried out with the help of analyzers. The central part of the analyzer is a certain zone in the cerebral cortex. The peripheral part is receptors that are located on the surface of the body to receive external information, or in internal organs.

external signals ® receptor ® nerve connections ® brain

Depending on the specifics of the received signals, there are: external (visual, auditory, pain, temperature, olfactory, gustatory) and internal (vestibular, pressure, kinesthetic) analyzers.

The main characteristic of analyzers is sensitivity.

The lower absolute threshold of sensitivity is the minimum value of the stimulus to which the analyzer begins to respond.

If the stimulus causes pain or disruption of the analyzer, this will be the upper absolute threshold of sensitivity. The interval from minimum to maximum determines the range of sensitivity (for example, for sound from 20 Hz to 20 kHz).

85-90% of all information about external environment a person receives through a visual analyzer. Reception and analysis of information is carried out in the range (light) - 360-760 electromagnetic waves. The eye can distinguish 7 primary colors and more than a hundred shades. The eye is sensitive to the visible range of the spectrum of electromagnetic waves from 0.38 to 0.77 microns. Within these limits, different wavelength ranges cause different sensations (colors) when exposed to the retina:

0.38 - 0.455 microns - purple;

0.455 - 0.47 microns - blue;

0.47 - 0.5 microns - blue;

0.5 - 0.55 microns - green;

0.55 - 0.59 µm - yellow;

0.59 - 0.61 µm - Orange color;

0.61 - 0.77 microns - red.

The highest sensitivity is achieved at a wavelength of 0.55 µm

The minimum intensity of light exposure that causes sensation. adaptation of the visual analyzer. The temporal characteristics of signal perception include: latent period - time from the signal to the moment of sensation 0.15-0.22 s.; signal detection threshold at higher brightness - 0.001 s, with flash duration - 0.1 s .; incomplete dark adaptation - from several seconds to several minutes.

With the help of sound signals, a person receives up to 10% of information. Auditory signals are used to focus a person's attention, to transmit information, to unload the visual system. Features of the auditory analyzer are:

- the ability to be ready to receive information at any time;

- the ability to perceive sounds in a wide range of frequencies and highlight the necessary ones;

- the ability to determine with accuracy the location of the sound source.

The perceptive part of the auditory analyzer is the ear, which is divided into three sections: outer, middle and inner. Sound waves, penetrating into the external auditory meatus, vibrate the tympanic membrane and through the chain of auditory ossicles are transmitted to the cavity of the cochlea of ​​the inner ear. Vibrations of the fluid in the canal cause the fibers of the main membrane to resonate with the sounds entering the ear. Vibrations of the cochlear fibers set in motion the cells of the organ of Corti located in them, a nerve impulse arises, which is transmitted to the corresponding sections of the cerebral cortex. Threshold pain 130 - 140 dB.

The skin analyzer provides perception of touch, pain, heat, cold, vibration.

Human analyzers and their main characteristics.

One of the main functions of the skin is protective (from mechanical, chemical damage, from pathogenic microorganisms, etc.). An important function of the skin is its participation in thermoregulation. 80% of the entire heat transfer of the body is carried out by the skin. At a high temperature of the external environment, the skin vessels expand (heat transfer increases), at a low temperature, the vessels narrow (heat transfer decreases). The metabolic function of the skin is to participate in the processes of regulation of the general metabolism in the body (water, mineral, carbohydrate). Secretory function is provided by the sebaceous and sweat glands. Endogenous poisons, microbial toxins can be released with sebum.

The olfactory analyzer is designed for human perception of various odors (range up to 400 items). The receptors are located on the mucous membrane in the nasal cavity. The conditions for the perception of odors are the volatility of an odorous substance, the solubility of substances. Odors can signal a person about violations of technological processes.

There are four types of taste sensations: sweet, sour, bitter, salty, and other combinations of them. The absolute thresholds of the gustatory analyzer are 1000 times higher than those of the olfactory one. The mechanism of perception of taste sensations is associated with chemical reactions. It is assumed that each receptor contains highly sensitive protein substances that decompose when exposed to certain flavoring substances.

The sensitivity of the taste analyzer is rough, averaging 20%. Recovery of taste sensitivity after exposure to various stimuli ends in 10-15 minutes

External analyzers

Reception and analysis of information is carried out with the help of analyzers. The central part of the analyzer is a certain zone in the cerebral cortex. The peripheral part is receptors that are located on the surface of the body to receive external information, or in internal organs.

external signals ® receptor ® nerve connections ® brain

Depending on the specifics of the received signals, there are: external (visual, auditory, pain, temperature, olfactory, gustatory) and internal (vestibular, pressure, kinesthetic) analyzers.

The main characteristic of analyzers is sensitivity.

The lower absolute threshold of sensitivity is the minimum value of the stimulus to which the analyzer begins to respond.

If the stimulus causes pain or disruption of the analyzer, this will be the upper absolute threshold of sensitivity. The interval from minimum to maximum determines the range of sensitivity (for example, for sound from 20 Hz to 20 kHz).

A person receives 85-90% of all information about the external environment through a visual analyzer. Reception and analysis of information is carried out in the range (light) - 360-760 electromagnetic waves. The eye can distinguish 7 primary colors and more than a hundred shades. The eye is sensitive to the visible range of the spectrum of electromagnetic waves from 0.38 to 0.77 microns. Within these limits, different wavelength ranges cause different sensations (colors) when exposed to the retina:

0.38 - 0.455 microns - purple;

0.455 - 0.47 microns - blue;

0.47 - 0.5 microns - blue;

0.5 - 0.55 microns - green;

0.55 - 0.59 microns - yellow;

0.59 - 0.61 microns - orange;

0.61 - 0.77 microns - red.

The highest sensitivity is achieved at a wavelength of 0.55 µm

The minimum intensity of light exposure that causes sensation. adaptation of the visual analyzer. The temporal characteristics of the perception of signals include: latent period - the time from the signal to the moment the sensation occurs 0.15-0.22 s .; signal detection threshold at higher brightness - 0.001 s, with flash duration - 0.1 s .; incomplete dark adaptation - from several seconds to several minutes.

With the help of sound signals, a person receives up to 10% of information. Auditory signals are used to focus a person's attention, to transmit information, to unload the visual system. Features of the auditory analyzer are:

The ability to be ready to receive information at any time;

The ability to perceive sounds in a wide range of frequencies and highlight the necessary ones;

The ability to accurately locate the source of a sound.

The perceptive part of the auditory analyzer is the ear, which is divided into three sections: outer, middle and inner. Sound waves, penetrating into the external auditory meatus, vibrate the tympanic membrane and through the chain of auditory ossicles are transmitted to the cavity of the cochlea of ​​the inner ear. Vibrations of the fluid in the canal cause the fibers of the main membrane to resonate with the sounds entering the ear. Vibrations of the cochlear fibers set in motion the cells of the organ of Corti located in them, a nerve impulse arises, which is transmitted to the corresponding sections of the cerebral cortex. Pain threshold 130 - 140 dB.

The skin analyzer provides perception of touch, pain, heat, cold, vibration. One of the main functions of the skin is protective (from mechanical, chemical damage, from pathogenic microorganisms, etc.). An important function of the skin is its participation in thermoregulation. 80% of the entire heat transfer of the body is carried out by the skin. At a high temperature of the external environment, the skin vessels expand (heat transfer increases), at a low temperature, the vessels narrow (heat transfer decreases). The metabolic function of the skin is to participate in the processes of regulation of the general metabolism in the body (water, mineral, carbohydrate). Secretory function is provided by the sebaceous and sweat glands. Endogenous poisons, microbial toxins can be released with sebum.

The olfactory analyzer is designed for human perception of various odors (range up to 400 items). The receptors are located on the mucous membrane in the nasal cavity. The conditions for the perception of odors are the volatility of an odorous substance, the solubility of substances. Odors can signal a person about violations of technological processes.

Analyzers are a system of sensitive nerve formations that analyze and synthesize changes that occur in the external environment and in the body.

According to I.P. Pavlov, the analyzer consists of three sections: peripheral, that is, perceiving (receptor, or sensory organ), intermediate, or conductive (pathways and intermediate nerve centers), and central, or cortical ( nerve cells cerebral cortex). The peripheral section of the analyzers includes everything, as well as receptor formations and free nerve endings located in the internal organs and muscles.

The receptor apparatus of each analyzer is adapted to transform the energy of a certain type of irritation into nervous excitation (see). In the cortical section of the analyzer, nervous excitation turns into sensation. The activity of the cortical department provides adaptive reactions of the body to changes in the external environment.

Analyzers - a system of sensitive (afferent) nerve formations that analyze and synthesize the phenomena of the external and internal environment of the body. The term was introduced into the neurological literature, according to the ideas of which each analyzer consists of specific perceiving formations (see Receptors, Sensory Organs) that make up the peripheral section of the analyzers, the corresponding nerves that connect these receptors with different levels of the central nervous system (conductor part), and the cerebral end, represented by in higher animals in the cerebral cortex.

Depending on the receptor function, analyzers of the external and internal environment are distinguished. The first receptors are turned to the external environment and are adapted to analyze the phenomena occurring in the surrounding world. These analyzers include visual, hearing, skin, olfactory, gustatory (see Vision, Hearing, Touch, Smell, Taste). Analyzers of the internal environment are afferent nervous devices, the receptor apparatuses of which are located in the internal organs and are adapted to analyze what is happening in the body itself. These analyzers also include motor (its receptor apparatus is represented by muscle spindles and Golgi receptors), which provides the ability to accurately control the musculoskeletal system (see Motor reactions). An important role in the mechanisms of statokinetic coordination is also played by another internal analyzer - the vestibular one, which closely interacts with the analyzer of movement (see Body balance). The motor analyzer in humans also includes a special department that ensures the transmission of signals from the receptors of the speech organs to the higher floors of the central nervous system. Due to the importance of this department in the activity of the human brain, it is sometimes considered as a “speech-motor analyzer”.

The receptor apparatus of each analyzer is adapted to the transformation of a certain type of energy into nervous excitation. Thus, sound receptors selectively respond to sound stimuli, light to light stimuli, taste to chemical stimuli, skin to tactile-temperature stimuli, etc. individual elements already at the level of the peripheral part of the analyzer.

The most complex and subtle analysis, differentiation and subsequent synthesis of external stimuli are carried out in the cortical sections of the analyzers. Method conditioned reflexes in combination with the extirpation of the brain tissue, it was shown that the cortical sections of the analyzers consist of nuclei and scattered elements.

When the nuclei are destroyed, subtle analysis is disturbed, but coarse analytical-synthetic activity is still possible due to scattered elements. Such an anatomical and physiological organization ensures the dynamism and high reliability of the functions of the analyzers.

The biological role of analyzers lies in the fact that they are specialized tracking systems that inform the body about all events occurring in the environment and inside it. From the huge stream of signals that continuously enter the brain through external and internal analyzers, that useful information is selected that is essential in the processes of self-regulation (maintaining an optimal, constant level of body functioning) and the active behavior of animals in the environment. Experiments show that the complex analytical and synthetic activity of the brain, determined by the factors of the external and internal environment, is carried out according to the polyanalyzer principle. This means that the entire complex neurodynamics of cortical processes, which form the integral activity of the brain, is made up of a complex interaction of analyzers (see).

To maintain the "Man - Environment" system in a safe state, it is necessary to coordinate the actions of a person with the elements of the environment. A person communicates directly with the environment through the senses.

Sense organs are complex sensory systems (analyzers), including perceptive elements (receptors), nerve pathways and corresponding sections in the brain, where the signal is converted into sensation.

The main characteristic of the analyzer is sensitivity, which is characterized by the value of the sensation threshold. Distinguish between absolute and differential thresholds of sensation.

The absolute threshold of sensation is the minimum strength of irritation that can cause a reaction.

The differential sensation threshold is the minimum amount by which a stimulus must be changed in order to cause a change in response. Psychophysical experiments have established that the magnitude of sensations changes more slowly than the strength of the stimulus.

The time elapsed from the onset of exposure to the stimulus to the appearance of sensations is called the latent period. Let's consider some analyzers that affect the conditions of safe human activity.

visual analyzer

Approximately 70 to 90% of information about the outside world a person receives through vision. The organ of vision - the eye - has a high sensitivity. Changing the pupil size from 1.5 to 8 mm allows the eye to change sensitivity hundreds of thousands of times. The retina of the eye perceives radiation with wavelengths from 380 (violet) to 760 (red) nanometers (billionths of a meter).

When ensuring safety, it is necessary to take into account the time required for the adaptation of the eye. The adaptation of the visual analyzer to greater illumination is called light adaptation. It requires from 1-2 to 8-10 minutes. Adaptation of the eye to low light (dilation of the pupil and increase in sensitivity) is called tempo adaptation and requires 40 to 80 minutes.

During the period of adaptation of the eyes, human activity is associated with a certain danger. In order to eliminate the need for adaptation or reduce its impact, it is not allowed to use only one local lighting in a production environment. It is necessary to take measures to protect a person from the blinding effect of light sources and various shiny surfaces, to arrange vestibules when moving from a dark room (for example, in photo labs) to a normally lit one, etc.

Vision is characterized by sharpness, that is, the minimum angle at which two points are still visible as separate). Visual acuity depends on illumination, contrast and other factors. The calculation of graphic accuracy is based on physiological visual acuity.

The binocular field of view covers 120-160 degrees in the horizontal direction, vertically: up - 55-60 degrees, down - 65-72 degrees. The optimal visibility zone (taken into account when organizing a workplace) is limited by the field: up - 25 degrees, down - 35 degrees, to the right and left - 32 degrees each.

The error in estimating the distance up to 30 meters averages 12%.

The sensation caused by the light signal is stored in the eye due to the inertia of vision up to 0.3 seconds. The inertia of vision generates a stroboscopic effect - a feeling of continuity of movement at an image change rate of about 10 times per second (cinematography), visual perception of the rotation of the car's wheels in the opposite direction and other optical illusions.

The stroboscopic effect can be dangerous. For example, due to their lack of inertia, gas-discharge lighting lamps can create a dangerous situation. fluctuations electrical voltage create fluctuations in the light flux. The apparent stop of a rotating object is observed when the frequencies of rotation of the object and the vibrations of light are equal. When the frequency of flashes of light is greater than the number of revolutions of a rotating object, an illusion of rotation in the opposite direction from reality is created.

Light-sensitive cells (analyzers) of the eye are shaped like small rods and cones. The human retina contains about 130 million rods and 6-7 million cones. Thanks to sticks, a person sees at night, but vision is colorless (achromatic), which is why the expression arose: "All cats are gray at night." And vice versa - during the day the main role belongs to the cones, respectively, during the day color (chromatic) vision.

From the standpoint of safety, all deviations from the norm in the perception of color should be taken into account. These deviations include: color blindness, color blindness and hemeralopia ("night blindness"). A person suffering from color blindness perceives all colors as gray. Color blindness is a special case of color blindness. Color blind people usually do not distinguish between red and green, and sometimes yellow and purple. They see these colors as grey.

Statistically, approximately 5% of men and 0.5% of women are color blind. People who are colorblind cannot work where signal colors are used for safety reasons (for example, by drivers). A person suffering from hemeralopia loses the ability to see in dim (twilight, night) lighting.

Colors have a different psycho-physiological effect on a person, which must be taken into account when ensuring security and in technical aesthetics.

Touch

The skin is a complex organ that performs many protective and defensive functions. It protects the blood from the penetration of chemicals into it, preventing poisoning of the body, acts as a body temperature regulator, protecting the body from overheating and hypothermia.

The skin serves as the first protective barrier at the moment the current-carrying conductor touches the body. Possessing a high electrical resistance, sometimes reaching tens of thousands of ohms, the skin, at the first moment, prevents the passage electric current through the internal organs, which allows other types of body defenses to turn on.

Functional violation of 30-50% of the skin, in the absence of special medical care, leads to the death of a person.

There are about 500 thousand points on the skin - tactile analyzers that perceive sensations that arise when various mechanical stimuli (touch, pressure) are exposed to the skin surface. In addition, there are unevenly distributed analyzers on the skin that perceive pain, heat and cold.

The highest sensitivity on the distal parts of the body (furthest from the axis of the body).

The tactile analyzer has a high capacity for spatial localization. Its characteristic feature is the rapid development of adaptation (addiction), i.e. loss of feeling of touch or pressure. The adaptation time depends on the strength of the stimulus, for different parts of the body it ranges from 2 to 20 seconds. Thanks to adaptation, we do not feel the touch of clothes on the body.

Temperature sensitivity

Temperature sensitivity is characteristic of organisms that have a constant body temperature, achieved by thermoregulation. The skin temperature is lower than the internal body temperature (approximately 36.6°C) and is different for individual areas (forehead 34-35, on the face 20-25, on the stomach 34, on the soles of the feet 25-27°C).

There are two types of temperature analyzers in human skin: some react only to cold, others only to heat. In total, there are about 30 thousand heat points and approximately 250 thousand cold points on the skin.

The threshold for the perception of heat and cold is different, for example, heat points distinguish a temperature difference of 0.2, and cold points of 0.4 ° C. The time it takes to feel the temperature is approximately 1 second. Temperature analyzers, protecting the body from overheating and hypothermia, help maintain a constant body temperature.

Smell

The smell can serve as a warning signal of danger. Everyone knows how dangerous gases are. To recognize dangerous, odorless gases, special strongly smelling substances, odorants, are added to them. There are no widely used devices for measuring the strength of smell yet. However, our nose instantly feels even the smallest fractions of odorous substances.

Humans have about 60 million olfactory cells. They are located in the mucous membrane of the nasal conchas on an area of ​​​​approximately 5 cm2. The cells are covered with a huge number of hairs 30-40 angstroms (3-4 nanometers) long. The area of ​​their contact with odorous substances is 5-7 m2. Nerve fibers depart from the olfactory cells, sending signals about odors to the brain.

If the analyzers get a substance dangerous to life or threatening human health (ether, ammonia, chloroform, etc.), reflexively slows down or breath is held for a short time.

Taste perception

In physiology and psychology, the four-component theory of taste is accepted, according to which taste has four main types: sweet, salty, sour and bitter. All other taste sensations are a combination of the main types.

Taste is perceived by special cell formations (similar to bulbs) located in the mucous membrane of the tongue.

The discriminative sensitivity of the taste analyzer is rather crude, however, taste sensations play a precautionary role in ensuring safety.

The taste analyzer is approximately 10 thousand times coarser than the sense of smell, individual perception of taste can vary up to 20%.

If you find yourself in an extreme situation, you can use the recommendation of yogis: when trying unfamiliar food, try to keep it in your mouth as long as possible, chewing slowly and listening to your feelings. If there is a clear desire to swallow, then try to take a chance.

muscle feeling

Human muscles have special receptors. They are called proprioceptors (from the Latin proprius - own). They send signals to the brain, telling them what state the muscles are in. In response, the brain sends impulses that coordinate the work of the muscles. Muscular feeling, given the effect of gravity, "works" constantly. Thanks to him, a person takes a more comfortable posture.