What is an analyzer: structure and principles of operation. General properties of analyzers

Analyzer- part of the nervous system, consisting of many neurons that carry out perception, holding and analysis of specific information.

Components of any analyzer:

1. Peripheral department- represented by the perceiving parts of the nervous system - receptors (sense organs - complex receptors).

2. conductor department- represented by afferent neurons, pathways and subcortical centers.

3. Central department- represented by areas of the cerebral cortex that perceive afferent signals.

General properties of analyzers

1. Layering- the presence of several layers of nerve cells, the first of which is associated with receptor elements, and the last with neurons of the associative zones of the cerebral cortex.

2. Multichannel- the presence in each of the layers of many (up to a million) nerve elements associated with many elements of the next layer, which in turn send nerve impulses to elements of an even higher level.

3. The presence of "sensory funnels"- unequal number of elements in neighboring layers.

BUT) converging funnel - layer of photoreceptors of the retina - 130 million cells; the next layer - ganglion cells - 1.3 million.

B) expanding funnel - the number of neurons in the projection area of ​​the visual cortex in 1000 times more than in the subcortical visual center.

- in a narrowing funnel - reduction of information transmitted to the brain;

- expanding funnel - for a more detailed and complex analysis of various features.

4. Differentiation of the analyzer vertically and horizontally:

a). Vertically - the formation of departments from several layers ( peripheral, conductive, central).

b). Horizontally - in each layer - different properties of receptors.

Main functions of analyzers:

1. Signal detection carried out receptors.

Receptor classification

a ) depending on the transmission of information to the brain from the external or internal environment(exteroreceptors, interoreceptors);

b) depending on the action of the stimulus directly on the receptors or at a distance(contact, remote);

in) depending on the physical nature of the stimulus - specific sensitivity(mechanoreceptors, thermoreceptors, chemoreceptors, photoreceptors, pain (nociceptive) receptors (pain can also be perceived by other receptors with superstrong irritation);

G) depending on the mechanism of the occurrence of excitation in the receptors (by converting the energy of irritation into the energy of nervous excitation):

- Primary sentient - olfactory, tactile, proprioreceptors (perception and transformation of energy takes place in a sensitive neuron);

-Secondary sentient - hearing, vision, taste, vestibular apparatus). There is a receptor (not a nerve cell) that perceives the signal.

2. Distinguishing signals.

To assess the change in intensity, temporal and spatial indicators of the stimulus, it is necessary to provide different responses to a minimal difference between stimuli. This minimal difference is distinction threshold.

According to Weber-Fechner law sensation increases in proportion to the logarithm of the increase in the intensity of irritation.

For spatial discrimination 2 signals, it is necessary that between the receptors excited by them there is at least one unexcited receptor.

The main function of which is the perception of information and the formation of appropriate reactions. In this case, information can come both from the environment and from within the organism itself.

General structure of the analyzer. The very concept of "analyzer" appeared in science thanks to the famous scientist I. Pavlov. It was he who first identified them as a separate organ system and identified a common structure.

Despite all the diversity, the structure of the analyzer is, as a rule, quite typical. It consists of a receptor section, a conductive part and a central section.

• The receptor or peripheral part of the analyzer is a receptor that is adapted to the perception and primary processing of certain information. For example, the ear curl responds to sound waves, the eyes to light, and skin receptors to pressure. In receptors, information about the impact of the stimulus is processed into a nerve electrical impulse.
• Conductor parts - sections of the analyzer, which are nerve paths and endings that go to the subcortical structures of the brain. An example is the optic nerve, as well as the auditory nerve.
• The central part of the analyzer is the area of ​​the cerebral cortex on which the received information is projected. Here, in the gray matter, the final processing of information and the choice of the most appropriate reaction to the stimulus are carried out. For example, if you press your finger to something hot, then the thermoreceptors of the skin will conduct a signal to the brain, from where the command will come to pull the hand back.

Human analyzers and their classification. In physiology, it is customary to divide all analyzers into external and internal. External analyzers of a person react to those stimuli that come from the external environment. Let's consider them in more detail.

• visual analyzer. The receptor part of this structure is represented by the eyes. The human eye consists of three membranes - protein, circulatory and nervous. The amount of light that enters the retina is regulated by the pupil, which is able to expand and contract. The beam of light breaks on the cornea, lens, and thus, the image hits the retina, which contains many nerve receptors - rods and cones. Thanks to chemical reactions, an electrical impulse is formed here, which follows and is projected in the occipital lobes of the cerebral cortex.
• auditory analyzer. The receptor here is the ear. Its outer part collects sound, the middle one is the path of its passage. The vibration moves through the sections of the analyzer until it reaches the curl. Here, vibrations cause the movement of otoliths, which forms a nerve impulse. The signal travels along the auditory nerve to the temporal lobes of the brain.
• Olfactory analyzer. The inner shell of the nose is covered with the so-called olfactory epithelium, the structures of which react to odor molecules, creating nerve impulses.
• Human taste analyzers. They are represented by taste buds - an accumulation of sensitive chemical receptors that respond to certain
• Tactile, pain, temperature human analyzers- represented by the corresponding receptors located in different layers of the skin.

If we talk about the internal analyzers of a person, then these are the structures that respond to changes within the body. For example, in muscle tissue there are specific receptors that respond to pressure and other indicators that change inside the body.

Another striking example is one that reacts to the position of the whole body and its parts relative to space.

It is worth noting that human analyzers have their own characteristics, and the effectiveness of their work depends on age, and sometimes on gender. For example, women distinguish more shades and aromas than men. Representatives of the strong half have more

Questions at the beginning of the paragraph.

Question 1. What is the uniqueness of vision?

The uniqueness of vision in comparison with other analyzers lies in the fact that it allows not only to identify an object, but also to determine its place in space, to monitor movements.

Question 2. How is the eyeball protected? What is its structure?

The front of the eye is protected by eyelids, eyelashes and eyebrows. Outside, the eyeball is enclosed in a protein membrane, or sclera, which in front passes into a transparent cornea. This is the strongest "lens" of the eye.

Behind the sclera is the choroid.

It is black, so that the light inside the eye does not scatter. In front of the eye, the choroid passes into the iris. The color of the iris determines the color of the eyes.

In the middle of the iris is a round hole - the pupil.

Question 3. What is the function of the eye muscles?

Thanks to the cells of smooth muscle tissue, the pupil can expand and contract, letting in the amount of light necessary to view the object.

Question 4. How does the visual analyzer function in general?

The visual analyzer not only allows one to perceive a three-dimensional image, since both the left and right parts of the object are simultaneously covered, but also to determine the distance to it. The further away an object, the smaller its image on the retina. This helps us determine the distance to an object.

Questions at the end of the paragraph.

Question 1. What are the functions of the eyebrows, eyelashes, eyelids, lacrimal glands?

Eyebrows protect the eyes from sweat droplets flowing down the forehead, eyelashes and eyelids protect the eyes from foreign particles (dust, grains of sand, midges, etc.). The lacrimal glands and upper eyelids protect the eyes from drying out.

Question 2. What is a pupil? What are its functions?

The pupil is a round hole that is located in the center of the iris and expands or contracts depending on the light. By changing the diameter of the pupil, the eye regulates the incoming light flow.

Question 3. How does the lens work?

The lens is located behind the pupil and adjacent to the iris. The ciliary muscle approaches it, which changes its curvature. Due to the change in the curvature of the lens, light rays reflected from objects located at different distances from the eye are focused on the retina, which ensures their clear image.

Question 4. Where are the cones and rods located? What are their properties?

Cones and rods - receptor cells of the eye, are located on the retina. The rods are relatively evenly distributed over it, while the cones are concentrated in the region of the macula, which is located directly opposite the pupil. The rods are capable of being excited very quickly already in weak twilight light, but they cannot perceive color. Cones are excited in bright light, but much more slowly, and are able to perceive color.

Question 5. What parts does the visual analyzer consist of and how does its cortical part work?

The visual analyzer consists of the visual receptor (eye), the optic nerve and the visual zone of the cerebral cortex, located in the occipital lobe. In the visual receptors, light energy is converted into nerve impulses. Nerve impulses travel through the optic nerve fibers to the brain. The visual pathways are arranged so that the left part of the visual field from both eyes falls into the right hemisphere of the cerebral cortex, and the right part of the visual field into the left. Images from both eyes enter the corresponding brain centers and create a single three-dimensional image.

In our article, we will look at what an analyzer is. Every second a person receives information from the environment. He is so accustomed to this that he does not even think about the mechanisms of its receipt, analysis, formation of a response. It turns out that complex systems are responsible for the implementation of this function.

What is an analyzer?

Systems that provide information about changes in the environment and the internal state of the body are called sensory. This term comes from the Latin word "sensus", which means "sensation". The second name of such structures is analyzers. It also reflects the main function.

What is a system that provides the perception of various types of energy, their conversion into nerve impulses and entry into the corresponding centers of the cerebral cortex.

Types of analyzers

Despite the fact that a person is constantly faced with a whole range of sensations, there are five sensory systems in total. The sixth sense is often called intuition - the ability to act without a logical explanation and foresee the future.

Allow to perceive with its help about 90% of information about the environment. This is an image of individual objects, their shape, color, size, distance to them, movement and location in space.

Hearing is essential for communication and transfer of experience. We perceive various sounds due to air vibrations. The auditory analyzer converts their mechanical energy into which is perceived by the brain.

Able to perceive solutions of chemicals. The sensations that it forms are individual. The same can be said about the olfactory sensory. The sense of smell is based on the perception of chemical irritants of the internal and external environment.

The last analyzer is touch. With its help, a person is able to feel not only the touch itself, but also pain and temperature changes.

General plan of the building

Now let's look at what an analyzer is from an anatomical point of view. Any sensory system consists of three sections: peripheral, conductive and central. The first is represented by receptors. This is the beginning of any analyzer. These sensitive formations perceive various types of energy. eyes are irritated by light. The olfactory and gustatory analyzers contain chemoreceptors. The hair cells of the inner ear convert the mechanical energy of vibrational movements into electrical energy. The tactile system is especially rich in receptors. They perceive vibration, touch, pressure, pain, cold and heat.

The conduction section consists of nerve fibers. Through numerous processes of neurons, impulses are transmitted from the working organs to the cerebral cortex. The latter is the central division of sensory systems. The bark has a high level of specialization. It distinguishes between motor, olfactory, gustatory, visual, auditory zones. Depending on the type of analyzer, the neuron delivers nerve impulses through the conduction section to a specific section.

Analyzer adaptation

It seems to us that we perceive absolutely all signals from the environment. Scientists say the opposite. If this were true, the brain would wear out much faster. The result is premature aging.

An important property of analyzers is their ability to adjust the level of action of the stimulus. This property is called adaptation.

If the sunlight is very intense, the pupil of the eye narrows. This is how the body reacts. And the lens of the eye is able to change its curvature. As a result, we can consider objects that are located at different distances. This ability of the visual analyzer is called accommodation.

A person is able to perceive sound waves only with a certain vibration value: 16-20 thousand Hz. Turns out we don't hear much. The frequency below 16 Hz is called infrasound. With its help, jellyfish learn about an approaching storm. Ultrasound is a frequency above 20 kHz. Although a person does not hear it, such vibrations can penetrate deep into the tissues. On special devices with the help of ultrasound, you can get pictures of the internal organs.

Compensation ability

Many people have disorders of certain sensory systems. The reasons for this can be both congenital and acquired. Moreover, if at least one of the departments is damaged, the entire analyzer stops functioning.

The body does not have internal reserves for its recovery. But one system can compensate for another. For example, blind people read by touch. Scientists have found that they hear much better than the sighted.

So, what is a system that ensures the perception of various types of energy from the environment, their transformation, analysis and the formation of appropriate sensations or reactions.

Human analyzers, which are a subsystem of the central nervous system (CNS), are responsible for the perception and analysis of external stimuli. Signals are perceived by receptors - the peripheral part of the analyzer, and are processed by the brain - the central part.

Departments

The analyzer is a collection of neurons, which is often called a sensory system. Any analyzer has three departments:

• peripheral - sensitive nerve endings (receptors), which are part of the sense organs (vision, hearing, taste, touch);
• conductive - nerve fibers, a chain of different types of neurons that conduct a signal (nerve impulse) from the receptor to the central nervous system;
• central - a part of the cerebral cortex that analyzes and converts the signal into sensation.

Rice. 1. Departments of analyzers.

Each specific analyzer corresponds to a certain area of ​​the cerebral cortex, which is called the cortical nucleus of the analyzer.

Kinds

Receptors, and accordingly analyzers, can be two kinds:

• external (exteroceptors) - are located near or on the surface of the body and perceive environmental stimuli (light, heat, humidity);
• internal (interoceptors) - are located in the walls of internal organs and perceive irritants of the internal environment.

Rice. 2. The location of the centers of perception in the brain.

The six types of external perception are described in the table “Human Analyzers”.

Rice. 3. Location of receptors in the skin.

The internal ones include pressure receptors, the vestibular apparatus, kinesthetic or motor analyzers.

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Monomodal receptors perceive one type of stimulation, bimodal - two types, polymodal - several types. For example, monomodal photoreceptors perceive only light, tactile bimodal - pain and heat. The vast majority of pain receptors (nociceptors) are polymodal.

Characteristics

Analyzers, regardless of type, have a number of common properties:

• high sensitivity to stimuli, limited by the threshold intensity of perception (the lower the threshold, the higher the sensitivity);
• difference (differentiation) of sensitivity, which makes it possible to distinguish stimuli by intensity;
• adaptation that allows you to adjust the level of sensitivity to strong stimuli;
• training, manifested both in a decrease in sensitivity, and in its increase;
• preservation of perception after the cessation of the stimulus;
• interaction of different analyzers with each other, allowing to perceive the completeness of the external world.

An example of a feature of the analyzer is the smell of paint. People with a low threshold for odors will smell more strongly and respond actively (lacrimation, nausea) than people with a high threshold. The analyzers will perceive a strong odor more intensely than other surrounding odors. Over time, the smell will not be felt sharply, because. adaptation will take place. If you constantly stay in a room with paint, then the sensitivity will become dull. However, after leaving the room for fresh air, for some time you will feel the smell of paint “imagining”.