1. The basic principles of the central nervous system. The structure, functions, methods of studying the central nervous system The basic principle of the functioning of the central nervous system is the process of regulation, control of physiological functions, which are aimed at maintaining the constancy of the properties and composition of the internal

Criteria for determining, methods and principles of studying the health of the child population The health of the child population consists of the health of individuals, but it is also considered as a characteristic of public health. Public health is more than just

HISTORY OF STUDYING BRONCHIAL ASTHMA Around the VIII century. BC e. - in the work of Homer "Iliad" refers to the disease, manifested by periodic attacks of labored breathing. It was recommended to wear an amulet of amber as a means of preventing an attack. FROM

Methods of studying taijiquan The movements in taijiquan gymnastics are quite complicated, besides, body turns are often performed, various movements of the legs, directions and much more. Beginners to practice, usually paying attention to their hands, forget about their legs,

Briefly about the history of the study of dysbiosis The smallest organisms have been of interest to scientists for a long time. The researchers have been studying the role of microbes living in the environment, as well as on the surface of the human body (skin and mucous membranes) and in some organs, from the end of the 19th century.

Methods of studying the functions of the digestive tract The secretory and motor activities of the gastrointestinal tract are studied both in humans and in animal experiments. A special role is played by chronic studies when the animal is previously

The most widely used methods of recording the bioelectric activity of individual neurons, the total activity of the neuron pool or the brain as a whole (electroencephalography), computed tomography (positron emission tomography, magnetic resonance imaging), etc.

Electroencephalography - this is registration from the surface of the skin  head or from the surface of the cortex (the last - in the experiment) total electric field of brain neurons upon excitation  (Fig. 82).

Fig. 82. Rhythms of the electroencephalogram: A - basic rhythms: 1 - α-rhythm, 2 - β-rhythm, 3 - θ-rhythm, 4 - σ-rhythm; B - EEG desynchronization reaction of the occipital region of the cerebral cortex when opening the eyes () and restoration of the α-rhythm when closing the eyes (↓)

The origin of the EEG waves is not well understood. It is believed that EEG reflects the LP of many neurons - EPSP, TPPS, trace - hyperpolarization and depolarization, capable of algebraic, spatial and temporal summation.

This point of view is universally recognized, while the participation of PD in the formation of the EEG is denied. So, for example, W. Willes (2004) writes: “As for action potentials, the ionic currents arising from them are too weak, fast, and unsynchronized to be recorded as EEG.” However, this statement is not supported by experimental facts. To prove it, it is necessary to prevent the occurrence of PD of all CNS neurons and to register EEG in the conditions of the occurrence of only EPSP and TPPS. But this is impossible. In addition, under natural conditions, EPSPs are usually the initial part of PD, so there is no reason to argue that PD does not participate in the formation of EEG.

In this way, EEG is the registration of the total electric field of PD, EPSP, TPPS, trace hyperpolarization and depolarization of neurons.

Four main physiological rhythms are recorded on the EEG: α-, β-, θ- and δ-rhythms, the frequency and amplitude of which reflect the degree of central nervous system activity.

When examining an EEG, the frequency and amplitude of the rhythm are described (Fig. 83).

Fig. 83. The frequency and amplitude of the rhythm of the electroencephalogram. T 1, T 2, T 3 - period (time) fluctuations; the number of vibrations in 1 sec is the rhythm frequency; And 1, And 2 - the amplitude of the oscillation (Kira, 2003).

Evoked Potential Method  (VP) consists in recording changes in the electrical activity of the brain (electric field) (Fig. 84) that occur in response to irritation of sensory receptors (the usual option).

Fig. 84. Evoked potentials in a person to a flash of light: P - positive, H - negative components of VP; digital indices mean the sequence of positive and negative components in the EP. The beginning of the recording coincides with the moment the flash of light is turned on (arrow)

Positron Emission Tomography  - a method of functional isotope mapping of the brain, based on the introduction of isotopes (13 M, 18 P, 15 O) into the bloodstream in conjunction with deoxyglucose. The more active the area of \u200b\u200bthe brain, the more it absorbs labeled glucose. The radioactive radiation of the latter is detected by special detectors. Information from the detectors is sent to a computer, which creates “slices” of the brain at a recorded level, reflecting the uneven distribution of the isotope due to the metabolic activity of the brain structures, which makes it possible to judge possible lesions of the central nervous system.

Magnetic resonance imaging allows you to identify actively working areas of the brain. The technique is based on the fact that after dissociation of oxyhemoglobin, hemoglobin acquires paramagnetic properties. The higher the metabolic activity of the brain, the greater the volumetric and linear blood flow in this area of \u200b\u200bthe brain and the lower the ratio of paramagnetic deoxyhemoglobin to oxyhemoglobin. In the brain there are many foci of activation, which is reflected in the heterogeneity of the magnetic field.

Stereotactic method. The method allows you to enter macro- and microelectrodes, a thermocouple into various structures of the brain. Coordinates of brain structures are given in stereotactic atlases. Using the introduced electrodes, it is possible to record the bioelectric activity of a given structure, irritate or destroy it; through microcannulas, chemicals can be introduced into the nerve centers or ventricles of the brain; using microelectrodes (their diameter less than 1 μm), brought close to the cell, it is possible to record the impulse activity of individual neurons and judge the participation of the latter in reflex, regulatory and behavioral reactions, as well as possible pathological processes and the use of appropriate therapeutic effects of pharmacological drugs.

Data on the functions of the brain can be obtained during operations on the brain. In particular, with electrical stimulation of the cortex during neurosurgical operations.

Questions for self-control

1. What are the three departments of the cerebellum and their constituent elements that are distinguished in a structurally functional sense? From which receptors do impulses enter the cerebellum?

2. What parts of the central nervous system does the cerebellum connect with using the lower, middle, and upper legs?

3. With the help of which nuclei and structures of the brain stem does the cerebellum realize its regulatory effect on the tone of skeletal muscles and the motor activity of the body? Is it stimulating or inhibitory?

4. What structures of the cerebellum are involved in the regulation of muscle tone, posture and balance?

5. What is the structure of the cerebellum involved in the programming of targeted movements?

6. What effect does the cerebellum have on homeostasis, how does homeostasis change when the cerebellum is damaged?

7. List the departments of the central nervous system and the structural elements that make up the forebrain.

8. What are the formations of the diencephalon. What is the skeletal muscle tone observed in a diencephalic animal (cerebral hemispheres removed), what is it expressed in?

9. What groups and subgroups do the thalamic nuclei divide into and how are they related to the cerebral cortex?

10. What are the names of neurons that send information to specific (projection) nuclei of the thalamus? What are the paths that form their axons called?

11. What is the role of the thalamus?

12. What are the functions of the non-specific nuclei of the thalamus?

13. What is the functional significance of the associative zones of the thalamus.

14. What are the nuclei of the middle and diencephalon that form the subcortical visual and auditory centers?

15. In the implementation of what reactions, in addition to regulating the functions of internal organs, does the hypothalamus take part?

16. What part of the brain is called the highest autonomic center? What is called Claude Bernard's thermal injection?

17. What groups of chemicals (neurosecrets) come from the hypothalamus to the anterior pituitary gland and what is their significance? What hormones enter the posterior pituitary gland?

18. What receptors perceiving deviations from the norm of the parameters of the internal environment of the body are found in the hypothalamus?

19. Centers for the regulation of what biological needs are found in the hypothalamus

20. What brain structures make up the striopallid system? What reactions arise in response to stimulation of its structures?

21. List the main functions in which the striatum plays an important role.

22. What are the functional relationships between the striatum and the pale globe? What motor disorders occur when the striatum is damaged?

23. What motor disorders occur when a pale ball is damaged?

24. What are the structural formations that make up the limbic system.

25. What is characteristic of the spread of excitation between the individual nuclei of the limbic system, as well as between the limbic system and the reticular formation? What does this provide?

26. From which receptors and departments of the central nervous system do afferent impulses come to various formations of the limbic system, where does the limbic system send impulses?

27. What are the effects of the limbic system on the cardiovascular, respiratory and digestive systems? By what structures are these influences realized?

28. Does the hippocampus play an important role in the processes of short-term or long-term memory? What experimental fact testifies to this?

29. Provide experimental evidence showing the important role of the limbic system in the species-specific behavior of the animal and its emotional reactions.

30. List the main functions of the limbic system.

31. The functions of the Peipec circle and the circle through the amygdala.

32. The cerebral cortex: ancient, old and new bark. Localization and functions.

33. The gray and white substance of the PBC. Functions?

34. List the layers of the new cortex and their functions.

35. Field Broadman.

36. Columnar organization of KBP for Mountcastle.

37. Functional division of the cortex: primary, secondary and tertiary zones.

38. Sensory, motor and associative zones of KBP.

39. What does the projection of general sensitivity in the cortex mean (Sensitive Penfield homunculus). Where are these projections in the cortex?

40. What does the projection of the motor system in the cortex mean (Penfield motor homunculus). Where are these projections in the cortex?

50. What are the somatosensory zones of the cerebral cortex, indicate their location and purpose.

51. What are the main motor zones of the cerebral cortex and their location.

52. What are the zones of Wernicke and Broca? Where are they located? What are the consequences of their violation?

53. What is meant by a pyramidal system? What is its function?

54. What is meant by extrapyramidal system?

55. What are the functions of the extrapyramidal system?

56. What is the sequence of interaction of the sensory, motor and associative zones of the cortex in solving problems of recognizing an object and pronouncing its name?

57. What is interhemispheric asymmetry?

58. What functions does the corpus callosum perform and why is it cut during epilepsy?

59. Give examples of violations of interhemispheric asymmetry?

60. Compare the functions of the left and right hemispheres.

61. List the functions of various lobes of the cortex.

62. Where in the cortex is praxis and gnosis carried out?

63. What modality neurons are in the primary, secondary and associative zones of the cortex?

64. Which zones occupy the largest area in the crust? Why?

66. In which zones of the cortex are visual sensations formed?

67. In which areas of the cortex are auditory sensations formed?

68. In which zones of the cortex do tactile and pain sensations form?

69. What functions will fall out in a person with violation of the frontal lobes?

70. What functions will fall out in a person with a violation of the occipital lobes?

71. What functions will fall out in a person with a violation of the temporal lobes?

72. What functions will fall out in a person with violation of the parietal lobes?

73. The functions of the associative areas of KBP.

74. Methods of studying the work of the brain: EEG, MRI, PET, the method of evoked potentials, stereotactic and others.

75. List the main functions of the KBP.

76. What is meant by plasticity of the nervous system? Explain the example of the brain.

77. What functions of the diencephalon will fall out if the cerebral cortex is removed in different animals?

2.3.15 . General characteristics of the autonomic nervous system

Autonomic nervous system  - This is part of the nervous system that regulates the functioning of internal organs, the lumen of blood vessels, metabolism and energy, homeostasis.

Departments of the ANS. Currently, two divisions of the ANS are generally recognized:  sympathetic and parasympathetic. In fig. 85 presents the departments of the ANS and the innervation of its departments (sympathetic and parasympathetic) of various organs.

Fig. 85. Anatomy of the autonomic nervous system. Organs and their sympathetic and parasympathetic innervation are shown. T 1 -L 2 - nerve centers of the sympathetic division of the ANS; S 2 -S 4 - nerve centers of the parasympathetic ANS in the sacral spinal cord, III – oculomotor nerve, VII – facial nerve, IX – glossopharyngeal nerve, X – vagus nerve — nerve centers of the parasympathetic ANS in the brain stem

Table 10 shows the effects of the sympathetic and parasympathetic divisions of the ANS on the effector organs with an indication of the receptor type on the cells of the effector organs (Chesnokova, 2007) (Table 10).

Table 10. The effect of the sympathetic and parasympathetic divisions of the autonomic nervous system on some effector organs

In recent years, compelling facts have been obtained that prove the presence of serotonergic nerve fibers that are part of the sympathetic trunks and enhance the contraction of the smooth muscles of the digestive tract.

Arc of the vegetative reflex  has the same links as the arc of the somatic reflex (Fig. 83).

Fig. 83. The reflex arc of the vegetative reflex: 1 - receptor; 2 - afferent link; 3 - the central link; 4 - efferent link; 5 - effector

But there are features of its organization:

1. The main difference is that the reflex arc of the ANS may lock out outside the central nervous system- intra or extraorgan.

2. Afferent link of the autonomic reflex arc It can be formed both by its own - vegetative, and somatic afferent fibers.

3. In the arc of the vegetative reflex segmentation is less pronounced, which increases the reliability of autonomic innervation.

Classification of Autonomic Reflexes  (for structural and functional organization):

1. Allocate central (various levels)  and peripheral reflexes, which are divided into intra and extraorgan.

2. Viscero-visceral reflexes  - changes in the activity of the stomach during filling of the small intestine, inhibition of the activity of the heart during irritation of the P-receptors of the stomach (Goltz reflex), etc. The receptive fields of these reflexes are localized in different organs.

3. Viscerosomatic reflexes  - a change in somatic activity upon excitation of sensory receptors of the ANS, for example, muscle contraction, movement of limbs with severe irritation of the gastrointestinal receptors.

4. Somatovisceral reflexes. An example is the Dagnini-Ashner reflex - a decrease in the heart rate with pressure on the eyeballs, a decrease in urination with painful skin irritation.

5. Interoceptive, proprioceptive and exteroceptive reflexes - according to the receptors of reflexogenic zones.

Functional differences of the ANS from the somatic nervous system.  They are associated with the structural features of the ANS and the degree of severity of the influence of the cerebral cortex on it. Regulation of the functions of internal organs using the ANS  can be carried out with a complete violation of its connection with the central nervous system, but less completely. The ANS effector neuron is located outside the central nervous system: either in extra- or in intraorgan vegetative ganglia forming peripheral extra- and intraorgan reflex arcs. In case of violation of the connection of muscles with the central nervous system, somatic reflexes are eliminated, since all motor neurons are in the central nervous system.

ANS effecton organs and tissues of the body not controlleddirectly   consciousness  (a person cannot arbitrarily control the frequency and strength of heart contractions, contractions of the stomach, etc.).

Generalized (diffuse) character of influence in the sympathetic division of the ANSdue to two main factors.

Firstly, most adrenergic neurons have long postganglionic thin axons that branch many times in the organs and form the so-called adrenergic plexuses. The total length of the terminal branches of the adrenergic neuron can reach 10-30 cm. On these branches along their course there are numerous (250-300 per 1 mm) extensions in which norepinephrine is synthesized, stored and back captured. When an adrenergic neuron is excited, norepinephrine is released from a large number of these extensions into the extracellular space, while it acts not on individual cells, but on many cells (for example, smooth muscle), since the distance to postsynaptic receptors reaches 1-2 thousand nm. One nerve fiber can innervate up to 10 thousand cells of the working organ. In the somatic nervous system, the segmental nature of innervation provides a more accurate sending of impulses to a specific muscle, to a group of muscle fibers. One motor neuron can innervate only a few muscle fibers (for example, in the muscles of the eye - 3-6, fingers - 10-25).

Secondly, postganglionic fibers are 50-100 times more than preganglionic fibers (there are more neurons in the ganglia of neurons than preganglionic fibers). In parasympathetic nodes, each preganglionic fiber is in contact with only 1-2 ganglionic cells. Small lability of the autonomic ganglia neurons (10-15 imp./s) and the rate of excitation in the autonomic nerves: 3-14 m / s in the preganglionic fibers and 0.5-3 m / s in the postganglionic; in somatic nerve fibers - up to 120 m / s.

In organs with double innervation effector cells receive sympathetic and parasympathetic innervation  (Fig. 81).

Each muscle cell of the gastrointestinal tract, apparently, has a triple extraorganic innervation - sympathetic (adrenergic), parasympathetic (cholinergic) and serotonergic, as well as innervation from neurons of the intraorgan nervous system. However, some of them, such as the bladder, receive mainly parasympathetic innervation, and a number of organs (sweat glands, muscles, raising hair, spleen, adrenal glands) only sympathetic.

The preganglionic fibers of the sympathetic and parasympathetic nervous systems are cholinergic  (Fig. 86) and form synapses with ganglionic neurons using ionotropic N-cholinergic receptors (mediator - acetylcholine).

Fig. 86. Neurons and receptors of the sympathetic and parasympathetic nervous system: A - adrenergic neurons, X - cholinergic neurons; solid line -  preganglionic fibers; dotted line -postganglionic

Receptors got their name (D. Langley) because of their sensitivity to nicotine: low doses excite ganglion neurons, large doses block it. Sympathetic ganglia  located extraorganized, Parasympathetic  - usually, intraorganically. In the vegetative ganglia, in addition to acetylcholine, there are neuropeptides: methenkefalin, neurotensin, CCK, substance R. They perform modeling role. N-cholinergic receptors are also localized on the cells of skeletal muscles, carotid glomeruli and the adrenal medulla. N-cholinergic receptors of neuromuscular compounds and autonomic ganglia are blocked by various pharmacological drugs. In the ganglia there are insertion adrenergic cells that regulate the excitability of ganglion cells.

Different mediators of postganglionic fibers of the sympathetic and parasympathetic nervous system are different.

The following methods for studying the functions of the central nervous system

1. The method of transection of the brain stem at various levels. For example, between the medulla oblongata and the spinal cord.

2. The method of extirpation (removal) or destruction of brain regions.

3. The method of irritation of various departments and centers of the brain.

4. Anatomical and clinical method. Clinical observations of changes in the functions of the central nervous system in case of damage to any of its departments, followed by a pathological study.

5. Electrophysiological methods:

but. electroencephalography - registration of brain biopotentials from the surface of the skin of the skull. The technique was developed and introduced into the clinic by G. Berger.

b. registration of biopotentials of various nerve centers; It is used together with a stereotactic technique, in which electrodes are inserted into a strictly defined core using micromanipulators.

at. method of evoked potentials, recording the electrical activity of brain regions during electrical stimulation of peripheral receptors or other regions;

6. intracerebral injection of substances using microinophoresis;

7. chronoreflexometry - determination of the time of reflexes.

Properties of nerve centers

The nerve center (SC) is the set of neurons in various parts of the central nervous system that provide for the regulation of any function of the body. For example, a bulbar respiratory center.

The following features are characteristic for conducting excitation through nerve centers:

1. Unilateral conduct. It goes from the afferent, through the intercalary to the efferent neuron. This is due to the presence of interneuronal synapses.

2. Central delay holding excitation. Those. excitation along the SC is much slower than along the nerve fiber. This is due to synaptic delay. Since there are most synapses in the central link of the reflex arc, there is the lowest speed. Based on this, the reflex time is the time from the onset of exposure to the stimulus to the appearance of the response. The longer the central delay, the longer the reflex time. However, it depends on the strength of the stimulus. The larger it is, the shorter the reflex time and vice versa. This is explained by the phenomenon of summation of excitations in synapses. In addition, it is determined by the functional state of the central nervous system. For example, with fatigue of the NC, the duration of the reflex reaction increases.

3. Spatial and temporal summation. Temporal summation occurs, as in synapses due to the fact that the more nerve impulses arrive, the more neurotransmitter is released in them, the higher the amplitude of EPSP. Therefore, a reflex reaction can occur on several consecutive subthreshold irritations. Spatial summation is observed when impulses from several neuron receptors go to the nerve center. Under the action of subthreshold stimuli, the resulting postsynaptic potentials are summed up and a propagating PD is generated in the neuron membrane.

4. Transformation of the excitation rhythm - a change in the frequency of nerve impulses when passing through the nerve center. Frequency may decrease or increase. For example, increasing transformation (increasing frequency) is due to dispersion and multiplication of excitation in neurons. The first phenomenon arises as a result of the separation of nerve impulses into several neurons, the axons of which then form synapses on one neuron (Fig.). The second, by the generation of several nerve impulses during the development of an exciting postsynaptic potential on the membrane of one neuron. The downward transformation is explained by the summation of several EPSPs and the occurrence of one AP in a neuron.

5. Post-tetanic potentiation, this is an increase in the reflex reaction as a result of prolonged excitation of center neurons. Under the influence of many series of nerve impulses passing with great frequency through the synapses. a large number of neurotransmitter is released in interneuronal synapses. This leads to a progressive increase in the amplitude of the exciting postsynaptic potential and prolonged (several hours) excitation of neurons.

6. Aftereffect, this is the delay in the end of the reflex response after the termination of the stimulus. It is associated with the circulation of nerve impulses through closed circuits of neurons.

7. The tone of the nerve centers is a state of constant increased activity. It is due to the constant supply of nerve impulses to the SC from peripheral receptors, the stimulating effect on the neurons of metabolic products and other humoral factors. For example, the manifestation of the tone of the corresponding centers is the tone of a certain muscle group.

8. Automation or spontaneous activity of nerve centers. Periodic or continuous generation by neurons of nerve impulses that arise in them spontaneously, i.e. in the absence of signals from other neurons or receptors. It is caused by fluctuations in metabolic processes in neurons and the effect of humoral factors on them.

9. The plasticity of the nerve centers. This is their ability to change functional properties. At the same time, the center acquires the ability to perform new functions or restore old ones after damage. The basis of plasticity N.Ts. lies the plasticity of synapses and membranes of neurons that can change their molecular structure.

10. Low physiological lability and fatigue. N.Ts. can conduct pulses of only a limited frequency. Their fatigue is explained by the fatigue of synapses and a deterioration in the metabolism of neurons.

Inhibition of the central nervous system

The phenomenon of central inhibition was detected by I.M. Sechenov in 1862. He removed the hemisphere of the brain from a frog and determined the time of the spinal reflex to irritation of the paw with sulfuric acid. Then to the thalamus, i.e. visual tubercles imposed a crystalline salt and found that the reflex time was significantly increased. This testified to the inhibition of the reflex. Sechenov concluded that the overlying N.Ts. when excited, the underlying ones slow down. Inhibition in the central nervous system prevents the development of excitation or weakens the flowing excitation. An example of inhibition is the cessation of a reflex reaction, against the background of the action of another stronger stimulus.

The unitary-chemical theory of inhibition was originally proposed. It was based on the Dale principle: one neuron - one neurotransmitter. According to it, inhibition is provided by the same neurons and synapses as excitation. Subsequently, the correctness of the binary chemical theory was proved. In accordance with the latter, inhibition is provided by special inhibitory neurons, which are intercalary. These are Renshaw cells of the spinal cord and Purkinje neurons in between. Inhibition in the central nervous system is necessary for the integration of neurons into a single nerve center.

The following mechanisms of inhibition are distinguished in the central nervous system:

1. The postsynaptic. It occurs in the postsynaptic membrane of soma and dendrites of neurons. Those. after the transmitting synapse. In these areas, axo-dendritic or axo-somatic synapses form specialized inhibitory neurons (Fig.). These synapses are glycinergic. As a result of the effect of GLI on the glycine chemoreceptors of the postsynaptic membrane, its potassium and chlorine channels open. Potassium and chlorine ions enter the neuron; TPPS develops. The role of chlorine ions in the development of TPPS is small. As a result of hyperpolarization, the neuron's excitability decreases. The conduction of nerve impulses through it ceases. The strychnine alkaloid can bind to the glycine receptors of the postsynaptic membrane and turn off inhibitory synapses. This is used to demonstrate the role of braking. After the introduction of strychnine, the animal develops cramps of all muscles.

2. Presynaptic inhibition. In this case, the inhibitory neuron forms a synapse on the axon of the neuron, suitable for the transmitting synapse. Those. such a synapse is axo-axonal (Fig.). The mediator of these synapses is GABA. Under the influence of GABA, the chlorine channels of the postsynaptic membrane are activated. But in this case, chlorine ions begin to leave the axon. This leads to a small local, but prolonged depolarization of its membrane. A significant part of the sodium channels of the membrane is inactivated, which blocks the conduction of nerve impulses along the axon, and hence the release of a neurotransmitter in the transmitting synapse. The closer the inhibitory synapse is located to the axon knoll, the stronger its inhibitory effect. Presynaptic inhibition is most effective in processing information, since excitation is not blocked in the entire neuron, but only at its one input. Other synapses located on the neuron continue to function.

3. Pessimal braking. Discovered by N.E. Vvedensky. It occurs at a very high frequency of nerve impulses. A persistent, long-term depolarization of the entire neuron membrane and inactivation of its sodium channels develops. A neuron becomes unexcited.

In the neuron, both inhibitory and exciting postsynaptic potentials can occur simultaneously. Due to this, the necessary signals are selected.

Similar information.

NERVOUS SYSTEM DEVELOPMENT IN FILO AND ONTOGENESIS

In accordance with the concept of nervousness adopted in Russian science, the nervous system plays a fundamental role in regulating all manifestations of the vital activity of the organism and its behavior. Human nervous system

· Controls the activities of various organs and systems that make up the whole organism;

· Coordinates the processes taking place in the body, taking into account the state of the internal and external gray hair, anatomically and functionally linking all parts of the body into a single whole;

· Through the senses, communicates with the environment, thereby ensuring interaction with it;

· Contributes to the formation of interpersonal contacts necessary for the organization of society.

The development of the nervous system in phylogenesis

Phylogenesis is the process of historical development of a species. Phylogenesis of the nervous system is the history of the formation and improvement of the structures of the nervous system.

In the phylogenetic series, there are organisms of varying degrees of complexity. Given the principles of their organization, they are divided into two large groups: invertebrates and chordates. Invertebrate animals are of different types and have different principles of organization. Chordates belong to the same type and have a general structure plan.

Despite the different levels of complexity of various animals, their tasks are confronting their nervous system. This is, firstly, the unification of all organs and tissues into a single whole (regulation of visceral functions) and, secondly, the provision of communication with the external environment, namely, the perception of its stimuli and the response to them (organization of behavior and movement).

The improvement of the nervous system in the phylogenetic series goes through concentration of nerve elements  in nodes and the appearance of long bonds between them. The next step is cephalization - the formation of the brain, which takes on the function of shaping behavior. Already at the level of higher invertebrates (insects) prototypes of cortical structures (mushroom bodies) appear, in which cell bodies occupy a superficial position. Higher chordates in the brain already have real cortical structures, and the development of the nervous system goes along the way corticolization, that is, the transfer of all the higher functions of the cerebral cortex.

So, unicellular animals do not have a nervous system, so perception is carried out by the cell itself.

Multicellular animals perceive environmental influences in various ways, depending on their structure:

1. using ectodermal cells (reflex and receptor), which are diffusely located throughout the body, forming a primitive diffuse , or reticular , nervous system (hydra, amoeba). When one cell is irritated, other deeply lying cells are involved in the response process. This is because all the receptive cells of these animals are interconnected by long processes, thereby forming a reticular nervous network.

2. with the help of groups of nerve cells (nerve nodes) and nerve trunks extending from them. Such a nervous system is called nodal   and allows you to involve a large number of cells (annelids) in the response process to irritation.

3. using a nerve cord with a cavity inside (neural tube) and nerve fibers extending from it. Such a nervous system is called tubular   (from lancelet to mammals). Gradually, the neural tube thickens in the head region and as a result the brain appears, which develops by complicating the structure. The trunk of the tube forms the spinal cord. Both from the spinal cord and from the brain, nerves depart.

It should be noted that with a complication of the structure of the nervous system, previous formations do not disappear. In the nervous system of higher organisms, there are also reticular, nodular, and tubular structures characteristic of the previous stages of development.

As the structure of the nervous system becomes more complicated, the behavior of animals becomes more complicated. If in unicellular and protozoan multicellular organisms, taxis is the general reaction of an organism to external stimulation, then reflexes appear with a complication of the nervous system. In the course of evolution, not only external signals, but also internal factors in the form of various needs and motivations acquire significance in the formation of animal behavior. Along with congenital forms of behavior, learning begins to play a significant role, which ultimately leads to the formation of rational activity.

The development of the nervous system in ontogenesis

Ontogenesis is the gradual development of a specific individual from the moment of birth to death. The individual development of each organism is divided into two periods, prenatal and postnatal.

Prenatal ontogenesis, in turn, is divided into three periods: germinative, germinal and fetal. The germination period in humans covers the first week of development from the moment of fertilization until implantation of the embryo into the uterine mucosa. The embryonic period lasts from the beginning of the second week to the end of the eighth week, that is, from the moment of implantation to the completion of the laying of organs. The fetal (fetal) period begins from the ninth week and lasts until birth. During this period, an intensive growth of the body occurs.

Postnatal ontogenesis is divided into eleven periods: 1-10 day - newborns; 10 day -1 year - chest age; 1-3 years - early childhood; 4-7 years - the first childhood; 8-12 years - the second childhood; 13-16 years - adolescence; 17-21 years - youthful age; 22-35 years old - the first adulthood; 36-60 years - the second adulthood; 61-74 years old; from 75 years old - senile age; after 90 years - long-livers. Ontogenesis ends with natural death.

The essence of prenatal ontogenesis. The prenatal period of ontogenesis begins from the moment of fusion of two gametes and the formation of a zygote. The zygote sequentially divides, forming a blastula, which in turn also divides. As a result of this division, a cavity is formed inside the blastula - the blastocele. After the formation of blastocoel, the process of gastrulation begins. The essence of this process is the movement of cells into the blastocele and the formation of a two-layer embryo. The outer layer of germ cells is called ectodermand the inner one endoderm. Inside the embryo, a cavity of the primary intestine is formed - gastrocel b. At the end of the gastrula stage, an embryo of the nervous system begins to develop from the ectoderm. This happens at the end of the second beginning of the third week of prenatal development, when the medullary (neural) plate separates in the dorsal section of the ectoderm. The neural plate initially consists of one layer of cells. Then they differentiate by spongioblastsof which the supporting tissue develops - neuroglia, and the neuroblasts from which neurons develop. Due to the fact that the differentiation of the cells of the plate occurs in different areas at different speeds, it turns into a neural groove, and then into a neural tube, on the sides of which ganglionic plates,  of which afferent neurons and neurons of the autonomic nervous system subsequently develop. After that, the neural tube is unfastened from the ectoderm and immersed in mesoderm  (third germinal leaf). At this stage, the medullary plate consists of three layers, which subsequently give rise to: the inner, ependymal extrusion of the cavities of the ventricles of the brain and the central canal of the spinal cord, the middle, the gray matter of the brain, and the outer (small cell), the white matter of the brain. Initially, the walls of the neural tube have the same thickness, then its lateral sections begin to thicken intensively, with the dorsal and ventral walls lagging behind in development and gradually sink between the side walls. Thus, the dorsal and ventral median grooves of the future spinal cord and medulla are formed.

From the earliest stages of the development of the organism, a close connection is established between the neural tube and myotomes  - those areas of the body of the embryo ( somites), of which muscles subsequently develop.

From the trunk of the neural tube, the spinal cord subsequently develops. Each segment of the body - somite, and there are 34-35 of them, there corresponds a certain section of the neural tube - neurometerfrom which the innervation of this segment is carried out.

At the end of the third - the beginning of the fourth week, the formation of the brain begins. Embryogenesis of the brain begins with the development in the rostral part of the neural tube of two primary brain vesicles: arncephalon and deuterocephalon. Then, at the beginning of the fourth week, the deuterocephalon in the embryo is divided into middle (mesencephalon) and rhomboid (rhombencephalon) bubbles. And the archencephalon at this stage turns into the anterior (prosencephalon) brain bubble. This stage of brain embryogenesis is called the stage of three cerebral bladders.

Then, at the sixth week of development, the stage of five cerebral bladders begins: the anterior cerebral bladder is divided into two hemispheres, and the rhomboid brain into the posterior and additional. The middle cerebral bladder remains undivided. Subsequently, the diencephalon forms under the hemispheres, the cerebellum and bridge form from the posterior bladder, and the additional bladder becomes the medulla oblongata.

Brain structures formed from the primary cerebral bladder: the middle, hind and extra brain - make up the brain stem. It is a rostral extension of the spinal cord and has common structural features with it. Motor and sensory structures, as well as vegetative nuclei, are located here.

Derivatives of the arncephalon create subcortical structures and cortex. Sensory structures are located here, but there are no autonomic and motor nuclei.

The diencephalon is functionally and morphologically associated with the organ of vision. Here, visual tubercles form - the thalamus.

The cavity of the medullary tube gives rise to the cerebral ventricles and the central canal of the spinal cord.

The stages of human brain development are shown schematically in Figure 18.

The essence of postnatal ontogenesis. Postnatal development of the human nervous system begins at the time of birth. The brain of a newborn weighs 300-400 g. Soon after birth, the formation of new neurons from neuroblasts ceases, the neurons themselves do not divide. However, by the eighth month after birth, brain weight doubles, by 4-5 years triple. The mass of the brain grows mainly due to an increase in the number of processes and their myelination. The maximum brain weight of men reaches 20-20 years, and women 15-19 years. After 50 years, the brain flattens, its weight drops and in old age can decrease by 100 g.

2. Research methods of the central nervous system

Central nervous system (CNS)  - the most complex of all functional systems of a person (Fig. Central and peripheral nervous system).

In the brain there are sensitive centers that analyze changes that occur both in the external and internal environment. The brain controls all body functions, including muscle contractions and secretory activity of the endocrine glands.

The main function of the nervous system is to quickly and accurately transmit information. The signal from the receptors to the sensory centers, from these centers to the motor centers and from them to the effector organs, muscles and glands, must be transmitted quickly and accurately.

Nervous system research methods

The main research methods of the central nervous system and neuromuscular system - electroencephalography (EEG), rheoencephalography (REG), electromyography (EMG), determine static stability, muscle tone, tendon reflexes, etc.

Electroencephalography (EEG)  - a method for recording electrical activity (biocurrents) of brain tissue for the purpose of objective assessment of the functional state of the brain. It is of great importance for the diagnosis of brain injury, vascular and inflammatory diseases of the brain, as well as for monitoring the functional state of an athlete, identifying early forms of neurosis, for treatment and for selection in sports sections (especially boxing, karate and other sports related striking the head).

When analyzing data obtained both at rest and under functional loads, various external influences in the form of light, sound, etc.), the amplitude of the waves, their frequency and rhythm are taken into account. In a healthy person, alpha waves predominate (oscillation frequency of 8-12 in 1 s), recorded only with the eyes of the subject being examined. In the presence of afferent light impulse, open eyes, alpha rhythm disappears completely and is restored again when the eyes close. This phenomenon is called the reaction of activation of the basic rhythm. Normally, it should be registered.

Beta waves have an oscillation frequency of 15-32 in 1 s, and slow waves are theta waves (with an oscillation range of 4-7 s) and delta waves (with an even lower oscillation frequency).

In 35-40% of people in the right hemisphere, the amplitude of alpha waves is slightly higher than in the left, there is also a certain difference in the frequency of oscillations - by 0.5-1 oscillation per second.

With head injuries, the alpha rhythm is absent, but fluctuations of high frequency and amplitude and slow waves appear.

In addition, the early signs of neurosis (overwork, overtraining) in athletes can be diagnosed by EEG.

Rheoencephalography (REG)  - a method for the study of cerebral blood flow, based on the registration of rhythmic changes in the electrical resistance of brain tissue due to pulse fluctuations in blood vessels.

Rheoencephalogram  composed of repetitive waves and cogs. When assessing it, the characteristics of the teeth, the amplitude of the rheographic (systolic) waves, etc. are taken into account.

The state of vascular tone can also be judged by the steepness of the ascending phase. Pathological indicators are a deepening of incisure and an increase in the dicrotic tooth with a shift downward along the descending part of the curve, which characterizes a decrease in the tone of the vessel wall.

The REG method is used in the diagnosis of chronic cerebrovascular disorders, vegetative-vascular dystonia, headaches and other changes in cerebral vessels, as well as in the diagnosis of pathological processes resulting from injuries, concussions and diseases that affect blood circulation in cerebral vessels (cervical osteochondrosis) , aneurysms, etc.).

Electromyography (EMG)  - a method for studying the functioning of skeletal muscles by recording their electrical activity - biocurrents, biopotentials. Electromyographs are used to record EMG. Abduction of muscle biopotentials is carried out using surface (overhead) or needle (injected) electrodes. In the study of limb muscles, electromyograms are most often recorded from the muscles of the same name on both sides. First, resting EM is recorded with the most relaxed state of the entire muscle, and then with its tonic tension.

According to EMG, it is possible to determine (and prevent the occurrence of muscle and tendon injuries) changes in muscle biopotentials at an early stage, and to judge the functional ability of the neuromuscular system, especially the muscles that are the most loaded in training. According to EMG, in combination with biochemical studies (determination of histamine, urea in the blood), early signs of neurosis (overwork, overtraining) can be determined. In addition, multiple myography determines the work of muscles in the motor cycle (for example, rowers, boxers during testing).

EMG characterizes muscle activity, the condition of the peripheral and central motor neuron.

EMG analysis is given by amplitude, shape, rhythm, potential oscillation frequency and other parameters. In addition, in the analysis of EMG, the latent period between giving a signal to muscle contraction and the appearance of the first oscillations on EMG and the latent period of the disappearance of oscillations after the command to stop contractions is determined.

Chronaximetry - a method for studying the excitability of nerves depending on the duration of the stimulus. First, reobase is determined - the current strength that causes a threshold contraction, and then - chronaxy. Chronance is the minimum current passage time by a force of two rheobases, which gives the minimum reduction. Chronaxia is calculated in sigma (thousandths of a second).

Normally, chronaxy of various muscles is 0.0001-0.001 s. It was found that proximal muscles have less chronaxia than distal ones. The muscle and its innervating nerve have the same chronaxy (isochronism). Synergist muscles also have the same chronaxy. On the upper extremities, the flexor muscle chronaxia is two times less than the extensor chronaxy; on the lower extremities, the opposite ratio is noted.

In athletes, chronaxia of muscles sharply decreases and the difference in chronaxia (anisochronaxia) of flexors and extensors can increase during overtraining (overwork), myositis, calf muscle paratenonitis, etc.

Stability in a static position can be studied using stabilography, tremorography, Romberg tests, etc.

Romberg test  reveals an imbalance in a standing position. Maintaining normal coordination of movements occurs due to the joint activities of several departments of the central nervous system. These include the cerebellum, the vestibular apparatus, the conductors of deep muscle sensitivity, the cortex of the frontal and temporal regions. The central organ of coordination of movements is the cerebellum. The Romberg test is carried out in four modes (Fig. Determination of balance in static poses) with a gradual decrease in the area of \u200b\u200bthe support. In all cases, the arms of the subject are raised forward, the fingers are apart and the eyes are closed. “Very good” if in each position the athlete maintains balance for 15 seconds and at the same time there is no swaying of the body, trembling hands or eyelids (tremor). With tremor, a satisfactory rating is given. If the equilibrium is disturbed for 15 s, then the sample is assessed as “unsatisfactory”. This test is of practical importance in acrobatics, gymnastics, trampolining, figure skating and other sports where coordination is important.

Regular training helps improve coordination. In a number of sports (acrobatics, gymnastics, diving, figure skating, etc.), this method is an informative indicator in assessing the functional state of the central nervous system and neuromuscular system. With overwork, head injury and other conditions, these indicators change significantly.

Yarotsky test  allows you to determine the sensitivity threshold of the vestibular analyzer. The test is performed in the initial position, standing with eyes closed, while the athlete on command starts rotational movements of the head at a fast pace. The time of head rotation until the athlete loses balance is recorded. In healthy individuals, the equilibrium time is on average 28 s, in trained athletes - 90 s or more.

The threshold level of sensitivity of the vestibular analyzer mainly depends on heredity, but under the influence of training it can be increased.

Finger-nasal test. The examinee is invited to touch the tip of the nose with his index finger open and then with his eyes closed. Normally, there is a hit, touching the tip of the nose. In case of brain injuries, neurosis (overwork, overtraining) and other functional conditions, oversight (miss), trembling (tremor) of the index finger or hand are noted.

Tapping test  determines the maximum frequency of brush movements.

For the test, you must have a stopwatch, a pencil and a sheet of paper, which are divided into four equal parts by two lines. For 10 seconds, set the points in the first square at the maximum pace, then a 10-second rest period and repeat the procedure from the second square to the third and fourth. The total test duration is 40 s. To evaluate the test, count the number of points in each square. Trained athletes have a maximum brush frequency of more than 70 in 10 seconds. The decrease in the number of points from square to square indicates a lack of stability of the motor sphere and nervous system. The decrease in the lability of nervous processes stepwise (with an increase in the frequency of movements in the 2nd or 3rd squares) - indicates a slowdown in the processes of workability. This test is used in acrobatics, fencing, in games and other sports.