The nervous system, together with the endocrine system, exercises control over all processes in the body, both simple and complex. It consists of the brain, spinal and peripheral nerve fibers.

HC classification

The nervous system is divided into: central and peripheral.

The central nervous system is the main part, it includes the spinal cord and brain. Both of these organs are reliably protected by the skull and spine. The PNS is a movement and sensory nerve. It ensures human interaction with the environment. With the help of the PNS, the body receives signals and reacts to them.

PNS is of two types:

• Somatic - sensory and motor nerve fibers. Responsible for the coordination of movement, a person can consciously control his body.
• Vegetative - divided into sympathetic and parasympathetic. The first responds to danger and stress. The second is responsible for rest, the normalization of the organs (digestive, urinary).

Despite their differences, both systems are interconnected and cannot work autonomously.

Properties of nervous processes

The classification of types of VND is influenced by the properties of nervous processes, these include:

• poise - the same course of processes in the central nervous system, such as arousal and inhibition;
• mobility - a quick change from one process to another;
• strength - the ability to respond correctly to a stimulus of any strength.

What are signaling systems

The signaling system is a set of reflexes that connect the body with the environment. They serve as a step in the formation of higher nervous activity.

Two signaling systems stand out:

1. reflexes to specific stimuli - light, sound (animals and humans have);
2. speech system - developed in a person in the process of labor activity.

Evolution of the central nervous system

The evolution of the functions of the cells of the central nervous system took place in several stages:

• improvement of individual cells;
• the formation of new properties capable of interacting with the environment.

The main stages of phylogenesis that the nervous system has gone through are:

1. The diffuse type is one of the oldest, it is found in organisms such as coelenterates (jellyfish). It is a type of network that consists of clusters of neurons (bipolar and multipolar). Despite its simplicity, the nerve plexuses, reacting to stimuli, give a reaction throughout the body. The speed at which the excitation spreads through the fibers is low.
2. In the process of evolution, a stem type emerged - a number of cells gathered into stems, but diffuse plexuses also remained. It is represented in the group of primorsomes (flatworms).
3. Further development led to the emergence of the nodal type - some of the cells of the central nervous system are collected in nodes with the possibility of transferring excitation from one node to another. The improvement of cells and the development of reception apparatuses took place in parallel. Nerve impulses arising in any part of the body do not spread throughout the body, but only within the segment. Representatives of this type are invertebrates: molluscs, arthropods, insects.
4. Tubular - higher, characteristic of chordates. Multi-synaptic connections appear, which leads to a qualitatively new relationship between the body and the environment. This type includes vertebrates: animals that are different in appearance and have a different way of life, and humans. They have a tube-like nervous system that ends in the brain.

Varieties

Scientist Pavlov has been conducting laboratory research for many years, studying the reflexes of dogs. He concluded that in humans, the type of nervous system mainly depends on congenital characteristics. It is the nervous system and its properties that physiologically affect the formation of temperament.

However, modern scientists argue that this is influenced not only by hereditary factors, but also by the level of education, training and social environment.

Thanks to all the studies, the following types of the nervous system have been identified, depending on the course of the processes of excitation, inhibition and being in balance:

1. Strong, unbalanced - choleric. In this type, excitation of the nervous system prevails over inhibition. Choleric people are very energetic, but they are emotional, hot-tempered, aggressive, ambitious and lack self-control.
2. Strong, balanced, agile - sanguine. People of this type are characterized as lively, active, easily adapt to different living conditions, have a high resistance to life's difficulties. They are leaders, and confidently go to their goal.
3. Strong, balanced, inert - phlegmatic. He is the opposite of a sanguine person. His reaction to everything that happens is calm, he is not prone to violent emotions, I am sure that he has great resistance to problems.
4. The weak is melancholic. The melancholic is not able to resist any stimuli, regardless of whether they are positive or negative. Typical signs: lethargy, passivity, cowardice, tearfulness. With a strong irritant, behavior disturbance is possible. The melancholic is always in a bad mood.

Interestingly, psychopathic disorders are more common in people with a strong unbalanced and weak type of GNI.

How to determine a person's temperament

It is not easy to determine what type of human nervous system is, since it is influenced by the cerebral cortex, subcortical formations, the level of development of signaling systems and intelligence.

In animals, the type of NS is more influenced by the biological environment. For example, puppies taken from the same litter, but raised in different conditions, may have different temperaments.

Investigating the central nervous system and human psychology, Pavlov developed a questionnaire (test), after passing which, you can determine your belonging to one of the types of GNI, subject to the truthfulness of the answers.

The nervous system controls the activities of all organs. Its type affects the character and behavior of a person. People with a common type are similar in their reactions to certain situations in life.

Tubular type of the nervous system

In vertebrates, the formation of the nervous system is based on the neural tube located on the dorsal side of the embryo. The anterior end of the tube is usually widened to form the brain. The posterior cylindrical part is nothing more than the spinal cord. There is a hypothesis according to which the ancestors of chordates had a longitudinal dorsal stripe of the primary sensory epithelium. Then, in the course of evolutionary development, it began to plunge into the ectoderm, first forming an open groove, and then forming a closed neural tube. This hypothesis is confirmed by the pictures of early embryogenesis of vertebrates (Fig. 20).

In the course of the evolutionary development of vertebrates, the tubular nervous system undergoes a number of changes.

First, all further development follows the path cephalization - preferential development of the brain. If in a primitively arranged chordate animal - a lancelet - the head end is practically not developed, then already in cyclostomes there is a noticeable thickening of the neural tube at the head end. This rather primitive brain already consists of three sections: anterior, middle and posterior. The anterior section is associated with the development of the sense of smell, the middle section is associated with vision, and the posterior section is associated with mechanoreception. Have fish the diencephalon is also allocated, the cerebellum receives sufficient development. Have amphibians the forebrain is significantly increased due to the development of the hemispheres, the midbrain is well developed, which in this group of animals is the highest visual center.

Secondly, in highly organized vertebrates, a new section of the brain appears - the cerebral cortex (cloak of the telencephalon). This structure more and more subordinates the reflexes of the lower parts of the brain, exercises control over them. This stage is named corticalization(from lat. cortex- bark). Have reptiles the cerebral cortex appears. Brain development mammals characterized by increased development of the neocortex, the Varoliev bridge appears, the structures of the middle and medulla oblongata are improved (Fig. 21). Have higher mammals associative cortex zones are the highest center of integrative activity in the central nervous system.

Thus, an increase in the volume and complexity of the structure of the vertebrate brain regions are closely related to the development of sensory systems and integrative activity. Gradually, depending on the influx of sensory information, phylogenetically new formations appear in the existing parts of the brain, which take control of an increasing number of functions.

However, it should be noted that in vertebrates, including the higher ones, the features of the previous evolutionary types of nervous systems are preserved: ganglionic and diffuse.

So in the peripheral nervous system (somatic and autonomic), sensitive neurons form ganglia (spinal, sympathetic and parasympathetic). With the help of ganglionic structures in the human body, the work of evolutionarily ancient (in comparison with the psyche) structures is ensured. These are, first of all, perception (sensitivity, reception) and the autonomous activity of internal organs.

Also, the signs of a diffuse nervous system have been preserved in our body. It forms the third section of the autonomic nervous system - the metasympathetic nervous system (recall the first two sections: sympathetic and parasympathetic). This department ensures the autonomous work of the hollow internal organs. Neurons of the metasympathetic nervous system form microganglionic clusters within the walls of organs, coordinating their activity (for example, peristaltic bowel movements that ensure the movement of food). The processes taking place in the diffuse nervous system can be modified under the influence of the sympathetic and parasympathetic nervous systems.

- in the endoderm.

The peculiarity of the diffuse nervous system is that the activity spreads in any direction from any point of stimulation. Although this type of nervous system can be considered primitive, actions such as food, swimming, moving to shells of mollusks in anemones, etc., are far from simple.

In addition to the nervous network, jellyfish and anemones also have a system of long bipolar neurons that form chains. They are able to quickly transmit impulses over long distances without their attenuation, perhaps this allows organism carry out a general response to various stimuli.

In other invertebrate groups animals nerve networks exist along with nerve trunks. They are noted on various parts of the body - under the skin, in the pharynx or other parts of the intestine, as well as in the leg of mollusks or in the rays of needle-skinned beams.

Already in creepers, there is a tendency to the concentration of neurons in the area of ​​the oral disc, and in polyps, also in the sole. In jellyfish, nerve clusters are formed along the edge of the umbrella, and in certain places of the annular thickening - also clusters of nerve cells. They are called ganglia. The marginal ganglia of jellyfish represent the first step towards the formation of the central part of the nervous apparatus. They concentrate the perikaryons of nerve cells, and the ganglia themselves are connected by nerve cords with each other and with the periphery - sense organs and effectors. Cords (nerves) are made up of the axons of nerve cells located in the ganglia.

The next stage in the concentration of nerve elements and the complication of nervous apparatus is the formation of an orthogon in flatworms - stem nervous system... The most primitive of them have a diffuse nerve plexus. Then, longitudinal and transverse condensations appear in it, which are ordered and form a rectangular lattice of longitudinal and annular shafts - orthogon(fig. 38). This is the original form for most types of the nervous apparatus of the lower worms.

Like cnidarians, some groups of the flatworm type have neural networks. Their functional characteristics are the same as those of the cnidarians.

The evolution of the orthogon goes towards a decrease in the number of trunks with the displacement of an increasing number of nerve cells into the brain. Its appearance contributes to the integration of the organism. The more advanced in evolutionary with respect to invertebrates, the anterior ganglia are better developed. This is part of the overall process differentiation of the head, or cephalization... It is characteristic of bilaterally symmetrical animals, leading, as a rule, an active lifestyle. In such animals, the mouth opening and sensory organs are located at the front end of the body. In this case, the processing of signals from the sense organs (visual, olfactory, gustatory, etc.) is carried out by the head, or cerebral, ganglion. Its functions also include nervous control. food-extracting behavior and control reflexes... We can say that the brain "makes strategic decisions" and gives "commands".

The brain is formed either due to the thickening of one of the first rings of the primitive orthogon, or due to the accumulation of nerve cells in the anterior end of the body in the thickness of the parenchyma. Hence the differences in names: the first type of brain is called orthogonal, and second - endonic.

The nervous apparatus, similar to that described above, is characteristic of a number of invertebrates, in particular for roundworms. Apparently, the orthogon should be considered the initial type of the nervous apparatus of mollusks and ringed worms, since the larvae of the latter have a structure of the nervous system close to it.

Nodular nervous system

Of modern molluscs, the nervous apparatus of the side-nerves is the simplest. Their brains are very poorly developed. Two pairs of nerve trunks depart from it - pedal and pleuro-visceral, interconnected by a multitude of transverse commissures. This is the central nervous apparatus, besides it, all mollusks also have a peripheral nerve plexus.

Most molluscs have everything cells the central nervous apparatus are collected in compact, clear ganglia, and the sections of the trunks connecting the two ganglia are completely freed from nerve cells. The ganglia can be compared to telephone exchanges, and the intermediate sections are like bundles of wires. The nervous system of molluscs forms the so-called nodal (scattered-nodal) type, or complex ganglionic system... The ganglia in it are located at different levels. Common to them is ganglionization and shortening of the connecting longitudinal (connectives) and transverse (commissures) strands, as well as the central nervous system going deeper.

Annelids do not have the diffuse nerve plexus characteristic of molluscs. Their central nervous apparatus consists of the brain, or the supraesophageal ganglion, periopharyngeal connectives, and a pair of nerve trunks lying under the intestine and connected by transverse commissures. In most rings, the nerve trunks are completely ganglionized, and in a typical case, one pair of ganglia is formed in each segment of the body. Each pair energizes its own segment. In primitive ringlets, the abdominal trunks are widely spaced and connected by long transverse commissures so that a "ladder nervous system" is formed. In more highly organized representatives, there is a shortening of commissures and convergence of trunks, which ultimately leads to their fusion. In this case, the central nervous system takes the form of a chain, which is called abdominal nerve chain.

A similar type of nervous apparatus is found in arthropods. It is located deep inside the body and also consists of the brain, periopharyngeal connectives and the abdominal nerve cord (Fig. 39), but one pair of abdominal ganglia is included in the brain, forming its posterior part (tritocerebrum).

In contrast to annulus, in arthropods, the concentration of the abdominal nerve chain is widespread due to the shortening of the connectives and the fusion of successive metameric ganglia. Connectives are shortened to the same extent as peripheral nerves are lengthened. This achieves the centralization of the nervous apparatus - shortening the intercentral pathways. In some cases, typical for crayfish and insects, ganglia are concentrated only in the head and chest. The innervation of the abdomen is carried out by long peripheral nerves (Fig. 40).

In a centralized nervous system, like that which has cephalopods or arthropods, the mechanism of a quick response to stimulation is carried out according to the type of reflex arc, in the formation of which several neurons(fig. 41): sensitive, intermediate (associative) and motor... Any external stimulus causes changes in the perceiving organ, which in turn stimulates a sensitive neuron, from which an impulse through synapses enters the intermediate neuron, and from it - to the motor. The impulse travels along the axon of the motor neuron to the muscle fiber, which responds to the stimulus by contraction. Material from the site

In insects, the brain (supra-pharyngeal ganglion) is particularly difficult. It consists of three pairs of fused ganglia - protocerebrum, deutocerebrum and tritocerebrum... The most developed is the protocerebrum, which has several centers, including the coordinating centers of the nervous system. A pair of very large and complex visual lobes that innervate the compound eyes is associated with the protocerebrum. The deutocerebrum innervates the antennae, and the tritocerebrum innervates the upper lip.

The subopharyngeal ganglion consists of three pairs of fused ganglia and innervates the oral organs and the anterior intestine.

The concentration of the nervous system of the higher groups of insects is a vivid manifestation of the principle oligomerization(reducing the number of homologous organs and parts). It improves the nervous control of the body and, in general, contributes to an increase in the morphophysiological level of insects.

In addition to the central nervous system, insects also have peripheral and sympathetic nervous systems. Endocrine glands are associated with the latter - adjacent and cardiac bodies ( cm.Endocrine system, glands and insect hormones ).

Tubular nervous system of deuterostomes

All the types of nervous apparatus considered are characteristic of the so-called primary animals... Deuterostomes of invertebrates include echinoderms and pogonophores. All are secondarystomes. chordates, including vertebrates.

According to the structure of the nervous apparatus, the lower deuterostomes are at a low stage of development, differing from cnidarians mainly in that they have nerve plexuses not only in the ectoderm, but also in the epithelium of the intestine and coelom (secondary body cavity)... In chordates, the central nervous system is represented by a neural tube passing along the dorsal side of the animal. The anterior end of the tube is usually widened and forms the brain.

There are three main types of structural organization of the nervous system: diffuse, nodular (ganglionic) and tubular.

The diffuse nervous system is the most ancient, characteristic of coelenterates. It is a network-like connection of nerve cells that are relatively evenly scattered throughout the body. The primitiveness of such a system consists in the absence of its division into central and peripheral parts, in the absence of long pathways. The network conducts stimulation from neuron to neuron relatively slowly. The body's reactions to irritation are imprecise and vague. However, the multitude of connections between the elements of the diffuse nervous system ensures their wide interchangeability and thus greater reliability of functioning.

The nodular nervous system is typical of mollusk worms, arthropods. It is characterized by the concentration of bodies of nerve cells with the formation of ganglia (nodes). The bodies of neurons, concentrated in the ganglia, form the central part of the nervous system. The role of the nerve nodes in the head region sharply increases. Differentiation of neurons occurs in accordance with the various functions performed. The neurons, along the processes of which the impulse enters the nerve centers, are called centripetal (sensitive) or afferent, and the neurons, along the processes of which the impulse from the nerve centers is directed to the executive organs (muscles, gland), are called centrifugal (motor) or efferent. Nerve cells that perceive excitation from some neurons and transmit it to other nerve cells are called interneurons or interneurons. Due to the specialization of neurons, the nerve impulse began to be conducted along certain paths, which ensured the speed, accuracy of the body's reactions. Such a qualitatively new way of the body's response is called the reflex type of reaction.

The tubular nervous system is characteristic of chordates. This type of system provides the greatest accuracy, speed and locality of responses. It is characterized by the highest degree of concentration of nerve cells. The central nervous system is represented by the tubular spinal cord and brain. In the process of evolution, the development of the head regions of the brain intensified, and their regulatory role increased. A new section has developed in the brain of higher vertebrates - the cerebral cortex. It collects information from all sensory and motor systems, carries out the highest analysis and serves as an apparatus for conditioned reflex activity, and in humans - an organ of mental activity, thinking.

The “payment” for the centralization of the nervous system is its high vulnerability: damage to the centers leads, as a rule, to disruption of the functions of the body as a whole.