Fundamentals of neurophysiology. Valery Shulgovsky - Fundamentals of Neurophysiology

Fundamentals of neurophysiology.

With brief information about physiology, smoothly moving on to the topic: "Neurophysiology" . The term consists of 2 roots:

Neuro(neur., neuro)(Greek - neiros - vein, tendon, fiber, nerve) - this is an integral part of a compound word, denoting "related to the nerves, to the nervous system";

Physio(Greek fysis - nature), logic(Greek logos - knowledge).

Physiology is the science of the vital activity of an organism, of the processes occurring in their systems, organs, tissues, cells and their structural elements.

So, neurophysiology- this is chapter physiology of higher animals and humans, studying the mechanisms of activity nervous system and its main structural units - neurons.

And what is nervous system? Before getting familiar with the concept nervous system, let's introduce the terms CNS, PNS, ANS.

CNS - includes those parts of the nervous system that lie inside the skull and spinal column - this is the brain and spinal cord. Nerves enter and exit the CNS. If they are located outside the skull or spine, they become part of the PNS - the peripheral nervous system, consisting of nerves (nerve fibers), nerve nodes (ganglia), and nerve endings. All tissues and organs are connected and controlled by the central nervous system, and the peripheral nervous system acts as a conductor between them, although it itself is located outside the brain and spinal cord. Due to its functions, it is divided into somatic and vegetative.

Somatic the nervous system covers the entire skin and musculoskeletal system, while providing sensory and motor functions.

Vegetative nervous system responsible for activities glands of external and internal secretion, internal organs, the state of the lymphatic and circulatory system. Its functions extend to ensuring respiration, blood circulation, digestion, reproduction, substances in the body and its growth as a whole.

CNS and PNS can work perfectly on one's own, although are constituent parts and nervous system or are functioning with very limited control CNS.

Now let's talk about the concept "nervous system".

Nervous system- this is set of formations in animals and humans, carrying out permanent connection of the organism with the environment and mutual communication between organs. She is governs and coordinates all bodily functions.

What is included in the concept set of formations", this is - nerves, ganglia, sense organs, brain.

Nerve(Latin nervus - vein) is an anatomical formation consisting of bundles of nerve fibers surrounded by connective sheaths - provides the conduction of nerve impulses, this is the main part of the peripheral nervous system (PNS).

ganglia(Greek ganglion - knot, subcutaneous tumor) is a limited accumulation of neurons located along the course of the nerve. AT ganglia there are also nerve fibres, nerve endings and blood vessels.

sense organs- organs of vision, hearing, smell, taste, touch, consisting of sensitive (receptor) nerve cells and support structures. Sending information to CNS. They often contribute to the most perfect adaptation of the organism to the surrounding world.

Brain- the central part of the nervous system of animals and humans. Consists of nervous tissue: gray matter(cluster mainly nerve cells) and white matter(cluster mainly nerve fibers).

Back to definition "neurophysiology". We are introduced to the concept nervous system", and now - about its main structural units - neurons.

Neuron ( Greek neuron - fiber) is a nervous cell, consisting of:

a) body(som)- all animal and plant cells, with the exception of sex cells;

b) departing from it processes- relatively short dendrite ov and long axon.

Neuron– main structural and functional unit of the nervous system.

Neurons

a) carry out nerve impulses from receptors in CNS(sensitive neurons), from CNS to the executive organs (motor neurons);

b) connect among themselves several other nerve cells (intercalary neurons).

Neurons interact with each other and with the cells of the executive organs through synapses.

Getting to know the concept "neuron", we noted a number of terms: cell - dendrites - axons - receptors - synapses. Let's break down these terms.

Cell- it's elementary living system, the foundation structure and activity of all animals and plants. Cells exist as

a) independent organisms(protozoa, bacteria) and

b) as part of multicellular organisms that have genital cells for reproduction and

in) body cells(somatic), various in structure and function(nerve, bone, muscle, secretory).

By the way, in the body of a newborn, in humans, about 2 10¹² cells.

Each cell has two main parts: nucleus and cytoplasm, in which are organelles. Studying the structure and function of the cell cytology.

Nucleus(biological concept) is a vital part of plant and animal cells. Controls the synthesis of proteins (including enzymes) and through them all the physiological processes in the cell. Most cells contain one nucleus.

Cytoplasm(Greek kitos - vessel, plasma - contents) is an ionized gas in which the concentrations of positive and negative charges are equal.

So, cytoplasm is the extranuclear part of the protoplasm of animal and plant cells.

Organelles(or organelles) are the “organs” of protozoa that perform various functions: motor and contractile, receptor, attack and defense, digestive and secretory.

Cytology is the science of the cell. It studies the structure and functions of cells, their connections and relationships in organs and tissues in multicellular organisms, as well as unicellular ones. Cytology occupies a central position in a number of biological disciplines, is closely related to histology, anatomy, genetics, biochemistry, microbiology.

Dendrites- branching processes of a nerve cell (neuron) that perceive signals from other neurons, receptor cells, or directly from external stimuli. Conducts nerve impulses to the body of the neuron.

axon(Greek axon - axis) - neuritis, axial cylinder. This is a process of a nerve cell (neuron) that conducts nerve impulses from the body (soma) of the cell to the innervated organs and other cells. Bundles of axons form nerves.

synapses(Greek synapsis - connection) is the area of \u200b\u200bcontact (contact) of nerve cells with each other ( interneuronal synapse) or tissues innervated by them ( organ synapse).

Receptors(Greek recipere - to receive) is a specialized peripheral part of each analyzer: the terminal formations of afferent nerve fibers that perceive irritation from external (exteroreceptors) or from internal(interoreceptors) body environments and converting physical (mechanical, thermal) or chemical energy of stimuli into excitation(nerve impulses) transmitted along sensory nerve fibers to CNS.

So, we are familiar with the concept nervous system", which governs everyone physiological functions. Numerous functions of a complex animal organism are completed by various specialized authorities: digestive, respiratory, excretory, circulatory, locomotive, etc.

The existence of an organism as a whole is impossible without interactions, coordination different functions among themselves. Changes in the environment surrounding the body, continuous changes in its internal environment, require appropriate regulation intensity and quality functions all organs; individual cells that make up this or that organ could not act at the same time and in agreement without receiving impulses.

In the complex organism of higher animals and humans, the function perception changes in the external and internal environment and broadcast response to the executive bodies are carried out by special bodies nervous system.

The main property of the elements of the nervous tissue is excitability and ability transmit excitation in the form of nerve impulses at a distance.

Perception environmental changes occur in special organs - receptors. Any influence of the environment, all kinds of irritations: physical(light, sound, pressure, temperature, touch), chemical(from substances in a gaseous state in the air, in perceived food) recycled in nerve impulse.Alone neurons with their processes are directly connected with perceiving and executive bodies, other are transmission between other nerves.

The organs of the nervous system that perform their functions are:

- brain and spinal cord

Nerves of the brain.

Brain carries out centralized management organism and its connection with the external environment.

Nerves are conductors through which nerve impulses flow from the periphery of the body to the brain, and response, executive nerve impulses flow from the brain to the periphery. The vast majority of nerve cells (except sensitive) ganglia are concentrated in the gray matter of the brain and spinal cord.

Brain is a very complex entity. It has two main structures - subcortical region and cerebral cortex. Its functions brain implements on the basis activities these two structures, which is denoted by the term "higher nervous activity". concept GNI was formulated by the great Russian physiologist I.P. Pavlov, which for a person put an equal sign between the term "mental activity" and GNI. In man brain Provides to a large extent all the functions of the body.

Before talking about the structure of the brain, let's remember the terms: CNS- the main part of the nervous system, which is an accumulation of nerve cells ( neurons) and their processes and plays an important role in the implementation of reflex activity; comprises a) the brain which is located in the cavity of the skull and

b) spinal cord located in the spine.

PNS(peripheral nervous system) consists of:

- cranial nerves

- nerve plexuses,

Year of issue: 2000

Genre: Physiology

Format: DOC

Quality: OCR

Description: The human brain is extremely complex. Even now, when we know so much about the brain of not only humans, but also a number of animals, we are apparently still very far from understanding physiological mechanisms many mental functions. We can say that these issues are only included in the agenda of modern science. First of all, this applies to mental processes like thinking, perception of the surrounding world and memory, and many others. At the same time, the main problems that will have to be solved in the third millennium are now clearly defined. What can present modern science a person who is interested in how the human brain functions? First of all, there are several systems “working” in our brain, at least three. Each of these systems can even be called a separate brain, although in a healthy brain each of them works in close cooperation and interaction. What are these systems? These are the activating brain, the motivational brain, and the cognitive or cognitive (from Latin Cognitio - knowledge) brain. As already mentioned, it should not be understood that these three systems, like nesting dolls, are nested one inside the other. Each of them, in addition to its main function, for example, the activating system (the brain), both participates in determining the state of our consciousness, sleep-wake cycles, and is an integral part of the cognitive processes of our brain. Indeed, if a person has a disturbed sleep, then the process of learning and other activities is impossible. Violation of biological motivations may be incompatible with life. These examples can be multiplied, but the main idea is that the human brain is a single organ that provides vital activity and mental functions, however, for convenience of description, we will single out the three blocks indicated above in it.

"Fundamentals of Neurophysiology »

WHY DOES A PSYCHOLOGIST NEED TO KNOW THE PHYSIOLOGY OF THE BRAIN?
CURRENT SUCCESS IN HUMAN BRAIN RESEARCH
NEUROBIOLOGICAL APPROACH TO STUDY OF THE HUMAN NERVOUS SYSTEM
PHYSIOLOGY OF THE HUMAN BRAIN
DEVELOPMENT OF THE HUMAN NERVOUS SYSTEM
BRAIN FORMATION FROM FERTILIZATION TO BIRTH
CELL - BASIC UNIT OF NERVOUS TISSUE
GLIA MORPHOLOGY AND FUNCTION
NEURON
NEURON EXCITATION
CONDUCTING EXCITATION
SYNAPSE
NERVOUS SYSTEM MEDIATORS
OPIATE RECEPTORS AND BRAIN OPIOIDS
ACTIVATED SYSTEMS OF THE BRAIN
PHYSIOLOGICAL MECHANISMS OF SLEEP
MENTAL ACTIVITY IN SLEEP
PHYSIOLOGICAL MECHANISMS OF REGULATION OF AUTONOMIC FUNCTIONS AND INSTINCTIVE BEHAVIOR
PERIPHERAL PART OF THE AUTONOMIC NERVOUS SYSTEM
VEGETATIVE CENTERS OF THE BRAIN STEM
LIMBIC SYSTEM OF THE BRAIN
PHYSIOLOGY OF THE HYPOTHALAMUS
CONTROL OF THE FUNCTIONS OF THE ENDOCRINE SYSTEM
BODY TEMPERATURE REGULATION
CONTROL OF WATER BALANCE IN THE BODY
REGULATION OF EATING BEHAVIOR
REGULATION OF SEXUAL BEHAVIOR
NERVOUS MECHANISMS OF FEAR AND RAGE
PHYSIOLOGY OF THE TONGAL
PHYSIOLOGY OF THE HIPPOCAMPUS
NEUROPHYSIOLOGY OF MOTIVATIONS
STRESS
COGNITIVE BRAIN
PHYSIOLOGY OF MOVEMENTS
REFLECTOR LEVEL OF MOVEMENT ORGANIZATION
PHYSIOLOGY OF THE CEREbellum
NEUROPHYSIOLOGY OF THE STRAIARY SYSTEM
DOWNLOAD ENGINE CONTROL SYSTEMS
PHYSIOLOGY OF SENSORY SYSTEMS
NEUROPHYSIOLOGY OF THE VISUAL SYSTEM
NEUROPHYSIOLOGY OF THE AUDIOUS SYSTEM
NEUROPHYSIOLOGY OF THE SOMATOSENSORY SYSTEM
NEUROPHYSIOLOGY OF SENSORY WAYS OF THE SPINAL CORD
PHYSIOLOGY OF THE TRIGENETIC NEVER
NEUROPHYSIOLOGY OF THE OLFACTORY SYSTEM
NEUROPHYSIOLOGY OF TASTE
HIGHER FUNCTIONS OF THE NERVOUS SYSTEM
ASYMMETRY OF THE HEMISPHERES OF THE HUMAN BRAIN
TEMPORAL DEPARTMENTS OF THE BRAIN AND ORGANIZATION OF AUDIO PERCEPTION
Occipital regions of the brain and visual perception
PARTICIPATION OF THE CORTEX IN THE ORGANIZATION OF VISUAL SPATIAL SYNTHESIS
FRONTAL BRAIN AND REGULATION OF HUMAN MENTAL ACTIVITY

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Neurophysiology

Electronic textbook

According to GEF-VPO 2010

Katunova V.V.

Polovinkina E.O.

Nizhny Novgorod, 2013

Katunova V.V., Polovinkina E.O.,

Neurophysiology: Electronic textbook. - Nizhny Novgorod: NIMB, 2013.

This textbook is a brief adapted revision of the educational and methodological publication: Shulgovsky V.V. Fundamentals of neurophysiology: Textbook for university students. - M.: Aspect Press, 2005. - 277 p. nerve cell brain reflex

It outlines modern ideas about the function of cells and nervous regulation, as well as the complex hierarchical regulation of the main activities of the body.

This electronic textbook consists of several structural blocks. It includes the program of the course "Neurophysiology", a system for monitoring students' knowledge, a glossary and a list of the main scientific literature recommended for study within this discipline, as well as a supporting lecture notes.

The course introduces students to the basic principles of the work of the nervous tissue, the functioning of various structures of the central nervous system.

The main concepts of the course are the following: processes of excitation and inhibition, unconditioned and conditioned reflexes, integrative activity of the brain, psychophysiological foundations of behavior. This course is based on the theoretical positions of two domestic physiological schools - I.P. Pavlov and A.A. Ukhtomsky.

Much attention is paid to the study of the sensory and cortical organization of nervous processes in connection with the mental activity of a person, which helps to understand the mechanisms of the course of mental processes, the relationship between the mental and physiological components in behavior. Such an understanding is especially relevant due to the fact that it allows the student to realize the complex hierarchical structure of the functioning of the nervous system and the principles of its control of various body functions.

The material is presented with the expectation of using knowledge from the field of neurophysiology and physiology in psychological practice.

Neurophysiology is the basis for the subsequent development of such disciplines as: "Psychophysiology", "Physiology of higher nervous activity", "Clinical psychology".

INTRODUCTION

Neurophysiology is a branch of animal and human physiology that studies the functions of the nervous system and its main structural units - neurons. Using modern electrophysiological techniques, neurons, neural assemblies, nerve centers and their interaction are studied.

Neurophysiology is necessary for understanding the mechanisms of psychophysiological processes, the development of communicative functions, such as speech, thinking, attention. It is closely related to neurobiology, psychology, neurology, clinical neurophysiology, electrophysiology, ethology, neuroanatomy and other sciences dealing with the study of the brain.

The main difficulty in studying the human nervous system lies in the fact that its physiological processes and mental functions are extremely complex. Psychologists study these functions with their own methods (for example, with the help of special tests they study a person’s emotional stability, level of mental development and other properties of the psyche). The characteristics of the psyche are studied by the psychologist without being “linked” to brain structures, i.e., the psychologist is interested in the organization of the mental function itself, but not in how the individual parts of the brain work in the implementation of this function. Only relatively recently, several decades ago, technical possibilities appeared for studying the methods of physiology (registration of the bioelectric activity of the brain, the study of the distribution of blood flow, etc.) of certain characteristics of mental functions - perception, attention, memory, consciousness, etc. A set of new approaches to research of the human brain, the sphere of scientific interests of physiologists in the field of psychology and led to the emergence of these sciences in the border area new science- psychophysiology. This led to the interpenetration of two areas of knowledge - psychology and physiology. Therefore, a physiologist who studies the functions of the human brain needs knowledge of psychology and the application of this knowledge in his practical work. But a psychologist cannot do without recording and studying the objective processes of the brain with the help of electroencephalograms, evoked potentials, tomographic studies, etc.

1. Course program

1.1 Explanatory note

This program outlines the basics of neurophysiology in accordance with the requirements of the current Federal State Educational Standard for this discipline.

The main sections of the physiology of the central nervous system, its main directions, problems, and tasks are considered in detail. Any form of mental activity is largely determined by the activity of the human nervous system, therefore, knowledge of the basic laws of its functioning is absolutely necessary for psychologists. Most of the existing textbooks on the physiology of the central nervous system are decades old, and the specialized literature on the subject is not very accessible to students due to insufficient preparation and inaccessibility of the material. In the lecture course, students get acquainted not only with the established ideas about the work of the nervous system, but also with modern views on its functioning.

Appointment of discipline. This course is intended for students of higher educational institutions studying in the direction of "Psychology". The academic discipline "Neurophysiology" is an integral part of the basic (general professional) part of the professional cycle (B.2) of the BEP in the direction of training "030300 Psychology".

The purpose of studying the discipline. The discipline "Neurophysiology" involves the formation and development of students' ideas and skills to comprehend the most complex laws of the brain activity of higher animals and humans. Considering the laws of brain activity, which are based on the principle of reflex reflection of the external world, to understand the complex manifestations of the behavior of animals and humans, including mental processes.

Discipline tasks:

To form students' understanding of the most important patterns of brain activity;

About the reflex principle of functioning of the central nervous system;

On the physiological mechanisms underlying the behavior of animals and humans, including mental processes;

About the main scientific problems and controversial issues in modern neurophysiology;

To prepare students for the application of the acquired knowledge in the implementation of a specific physiological study.

Requirements for the level of preparation of a student who has completed the study of this discipline. As a result of mastering this discipline, the graduate should have the following general cultural competencies (OC):

ability and willingness to:

understanding modern concepts pictures of the world based on a formed worldview, mastering the achievements of the natural and social sciences, cultural studies (OK-2);

Possession of the culture of scientific thinking, generalization, analysis and synthesis of facts and theoretical positions (OK-3);

Using the system of categories and methods needed to solve typical tasks in various areas professional practice (OK-4);

Conducting bibliographic and information retrieval work with the subsequent use of data in solving professional problems and preparing scientific articles, reports, conclusions, etc. (OK-9);

professional competencies (PC):

ability and willingness to:

Application of knowledge in psychology as a science of psychological phenomena, categories and methods for studying and describing the patterns of functioning and development of the psyche (PC-9);

Understanding and setting professional goals in the field of research and practical activities(PC-10).

Components of formed competencies in the form of knowledge, skills, possessions. As a result of mastering the discipline "Neurophysiology", the student must:

Basic concepts of neurophysiology (according to the glossary);

The main processes of development and formation of ontogenesis, phylogenesis and microstructure of the nervous tissue;

The main concepts of the functional organization of an individual neuron, it is a population of neurons and the brain as a whole; anthropometric, anatomical and physiological parameters of human life in phylo- and sociogenesis.

Use the basic laws, patterns in the functional organization in the neurosubstrate of the brain;

Use biological parameters to understand the processes of human life;

Using the conceptual apparatus to state and represent the neuronal organization of various brain structures;

Analyze the hierarchical organization of building brain models

Depict the neuronal organization of the main blocks of the brain and sensory systems.

Modern information systems Internet for bibliographic and information retrieval work in the field of CNS anatomy;

The main theories and concepts about the functioning of an individual neuron, neuronal populations of sensory systems and the brain as a whole

The main schemes, models and designs of the neuronal organization of the central nervous system;

The main theories and concepts of the functional organization and development of the central and peripheral nervous system.

The basic disciplines for the course "Neurophysiology" are the anatomy of the central nervous system, anthropology, general psychology, general psychodiagnostics. To master the course, it is also necessary to have a general knowledge of biology (anatomy and physiology of humans and animals) within the framework of the requirements of the school curriculum.

Forms of work: classroom and workshops, independent preparation of students.

Classroom classes are conducted with the use of adequate means of visualization and activation of students' activities. The program highlights the logic and content of lectures and self-study. In it, students will find literature and tasks recommended for preparation on each topic.

Independent work. The study of educational material transferred from classroom studies to independent study and identification of information resources in scientific libraries and the Internet in the following areas:

Bibliography on problems of neurophysiology;

publications (including electronic ones) of sources on neurophysiology;

· scientific literature on topical problems of neurophysiology.

Logistics support of discipline. Lecture room with multimedia projector, laptop and interactive whiteboard.

Forms of control: programmed task, test.

Part 1. Introduction to the discipline

Physiology in the system of biological sciences. Subject and object of study of neurophysiology. methodological Scientific foundations of modern neurophysiology. Modern technology neurophysiological experiment.

The main stages in the development of neurophysiology. Leading domestic and foreign neurophysiologists, scientific schools.

Characteristics of the current stage of development of neurophysiology. Modern ideas about the functions of the central nervous system, the central mechanisms of regulation of behavior and mental functions.

Part 2. Physiology of the human brain

Chapter 2.1. The cell is the basic unit of nervous tissue

Neuron as a structural functional unit of the CNS. Structural and biophysical properties of the neuron. The concept of the propagation of potentials through conductor structures. Submission P.K. Anokhin on intraneuronal processing and integration of synaptic excitations. The concept of P.K. Anokhin on the integrative activity of a neuron.

Glia. Types of glial cells. Functions of glial cells.

The structure of synapses. Synapse classification. Mechanism of synaptic transmission of the CNS. Characteristics of presynaptic and post-synaptic processes, transmembrane ion currents, the place of occurrence of the action potential in the neuron. Features of synaptic transmission of excitation and conduction of excitation along the neural pathways of the central nervous system. CNS mediators.

Signs of the process of excitation. Central inhibition (I.M. Sechenov). The main types of central braking. presynaptic and postsynaptic inhibition. Reciprocal and reciprocal inhibition. Pessimal inhibition. Inhibition followed by excitation. Functional significance of inhibitory processes. Inhibitory neural circuits. Modern ideas about the mechanisms of central inhibition.

General principles of the coordination activity of the central nervous system. The principle of reciprocity (N.E. Vvedensky, Ch. Sherington). Irradiation of excitation in the CNS. Convergence of excitation and the principle of a common final path. Occlusion. Sequential induction. The principle of feedback and its physiological role. Properties of the dominant focus. Modern ideas about the integrative activity of the CNS.

Mediators of the nervous system. Opiate receptors and brain opioids.

Chapter 2.2. activating brain systems

Structural and functional organization of activating systems of the brain. Reticular formation, nonspecific nuclei of the thalamus, limbic system. The role of neurotransmitters and neuropeptides in the regulation of sleep and wakefulness. Characteristics of human sleep at night. The structure of the night sleep of an adult.

Chapter 2.3. Physiological mechanisms of regulation of vegetative functions and instinctive behavior

Structural and functional organization of the autonomic nervous system. Reflex arc of the autonomous reflex. Sympathetic and parasympathetic divisions of the autonomic nervous system. Metasympathetic nervous system and enteric division of the autonomic nervous system. Formation of the output signal in the autonomic nervous system: the role of the hypothalamus and the nucleus of the solitary tract. Neurotransmitters and cotransmitters of the autonomic nervous system. Modern ideas about the functional features of the autonomic nervous system.

Control of the functions of the endocrine system. Body temperature regulation. Control of water balance in the body. regulation of eating behavior. Reg at regulation of sexual behavior. Nervous mechanisms of fear and rage. Physiology of the tonsils. Physiology of the hippocampus. Neurophysiology of motivations. neurof and ziology of stress.

Part 3. Cognitive brain

Chapter 3.1. Physiology of movements

The reflex principle of the activity of the central nervous system. Reflex theory of I.P. Pavlov. The principle of determinism, the principle of structurality, the principle of analysis and synthesis in the activity of the central nervous system. Reflex and reflex arc (R. Descartes, J. Prohaska). Types of reflexes. Reflex arcs of somatic and autonomic reflexes. Properties of nerve centers. One-sided, delayed conduction of excitation through the nerve center. Dependence of the reflex response on the stimulation parameters. summation of excitations. Transformation of the rhythm of excitation. aftereffect. Fatigue of the nerve centers. The tone of the nerve centers. Unconditioned and conditioned reflexes (I.P. Pavlov).

Movement regulation. Muscles as effectors of motor systems. Muscular proprioceptors and spinal reflexes: stretch reflex. Spinal mechanisms of coordination of movements. Posture and its regulation. Arbitrary movements. Motor functions of the cerebellum and basal ganglia. The oculomotor system.

2. LECTURE SUMMARY

2. 1 Introduction to the discipline

2.1.1 History of the development of science

Neurophysiology is a special branch of physiology that studies the ness of the nervous system, arose much later. Almost to the second half of XIX century neurophysiology developed as experimental science based on the study of animals. Indeed, the "lower" (basic) manifestations of the activity of the nervous system are the same in animals and humans. Such functions of the nervous system include the conduction of excitation along the nerve fiber, the transition of excitation from one nerve cell to another (for example, nerve, muscle, glandular), simple reflexes (for example, flexion or extension of a limb), perception of relatively simple light, sound, tactile and other irritants and many others. Only at the end of the 19th century, scientists began to study some of the complex functions of respiration, maintaining a constant composition of blood, tissue fluid, and some others in the body. In carrying out all these studies, scientists did not find significant differences in the functioning of the nervous system, both as a whole and in its parts, in humans and animals, even very primitive ones. For example, at the dawn of modern experimental physiology, the main object was the frog. Only with the discovery of new research methods (primarily electrical manifestations of the activity of the nervous system) did the new stage in the study of brain functions, when it became possible to study these functions without destroying the brain, without interfering with its functioning, and at the same time studying the highest manifestations of its activity - the perception of signals, the functions of memory, consciousness, and many others.

The knowledge that physiology had 50-100 years ago concerned only the functioning of the organs of our body (kidneys, heart, stomach, etc.), but not the brain. The ideas of ancient scientists about the functioning of the brain were limited only by external observations: they believed that there were three ventricles in the brain, and ancient doctors “placed” one of the mental functions in each of them.

A turning point in understanding the functions of the brain came in the 18th century, when very complex watch mechanisms began to be made. For example, music boxes played music, dolls danced, played musical instruments. All this led scientists to believe that our brain is somewhat similar to such a mechanism. Only in the 19th century was it finally established that the functions of the brain are carried out according to the reflex (reflecto - “reflect”) principle. However, the first ideas about the reflex principle of the human nervous system were formulated back in the 18th century by the philosopher and mathematician Rene Descartes. He believed that the nerves are hollow tubes through which animal spirits are transmitted from the brain, the seat of the soul, to the muscles.

The forerunner of the emergence of neurophysiology was the accumulation of knowledge about the anatomy and histology of the nervous system. Ideas about the reflex principle of functioning of the National Assembly were put forward as early as the 17th century. R. Descartes, and in the XVIII century. and J. Prohaska, however, as a science, neurophysiology began to develop only in the first half of the 19th century, when experimental methods began to be used to study the nervous system. The development of neurophysiology was facilitated by the accumulation of data on the anatomical and histological structure of the nervous system, in particular the discovery of its structural unit - the nerve cell, or neuron, as well as the development of methods for tracing nerve pathways based on observation of the degeneration of nerve fibers after their separation from the body of the neuron.

At the beginning of the XX century. C. Bell (1811) and F. Magendie (1822) independently established that after transection of the posterior spinal roots, sensitivity disappears, and after transection of the anterior roots, movements disappear (i.e., the posterior roots transmit nerve impulses to the brain, and the anterior ones - from the brain). Following this, they began to widely use the cutting and destruction of various brain structures, and then their artificial stimulation to determine the localization of a particular function in the nervous system.

An important step was the discovery of I.M. Sechenov (1863) of central inhibition - a phenomenon when irritation of a certain center of the nervous system causes not its active state - excitation, but suppression of activity. As was shown later, the interaction of excitation and inhibition underlies all types of nervous activity.

In the 2nd half of the XIX - early XX centuries. detailed information was obtained about the functional significance of the various parts of the nervous system and the basic patterns of their reflex activity. A significant contribution to the study of the functions of the central nervous system was made by N.E. Vvedensky, V.M. Bekhterev and C. Sherrington. The role of the brain stem, mainly in the regulation of cardiovascular activity and respiration, was largely elucidated by F.V. Ovsyannikov and N.A. Mislavsky, as well as P. Flurans, the role of the cerebellum - L. Luciani. F.V. Ovsyannikov determined the role of the brain stem and its influence on cardiovascular activity and respiration, and L. Luciani - the role of the cerebellum.

The experimental study of the functions of the cerebral cortex of the cerebral hemispheres was begun somewhat later (German scientists G. Fritsch and E. Gitzig, 1870; F. Goltz, 1869; G. Munch and others), although the idea of the possibility of extending the reflex principle to the activity of the cortex was developed as early as 1863 by Sechenov in his Reflexes of the Brain.

A consistent experimental study of the functions of the cortex was started by I.P. Pavlov, who discovered conditioned reflexes, and thus the possibility of objective registration of nervous processes occurring in the cortex.

I.P. Pavlov developed the idea of I.M. Sechenov in the form of "the doctrine of the physiology conditioned reflexes". He is credited with creating the method of experimental research " top floor» cerebral cortex - cerebral hemispheres. This method is called the "method of conditioned reflexes". He established the fundamental pattern of presenting to an animal (I.P. Pavlov conducted studies on dogs, but this is also true for humans) of two stimuli - first conditional (for example, the sound of a buzzer), and then unconditional (for example, feeding a dog with pieces of meat). After a certain number of combinations, this leads to the fact that, under the action of only the sound of the buzzer (conditional signal), the dog develops a food reaction (saliva is released, the dog licks, whines, looks towards the bowl), i.e., a food conditioned reflex has formed. Actually, this technique during training has long been known, but I.P. Pavlov made it a powerful tool for the scientific study of brain functions.

Physiological studies, combined with the study of the anatomy and morphology of the brain, led to an unequivocal conclusion - it is the brain that is the instrument of our consciousness, thinking, perception, memory and other mental functions.

Along with this, a direction arose in neurophysiology, which set itself the task of studying the mechanism of activity of nerve cells and the nature of excitation and inhibition. This was facilitated by the discovery and development of methods for recording bioelectric potentials. Registration of the electrical activity of the nervous tissue and individual neurons made it possible to objectively and accurately judge where the corresponding activity appears, how it develops, where and with what speed it spreads through the nervous tissue, etc. Especially contributed to the study of the mechanisms of nervous activity G. Helmholtz, E. Dubois-Reymond, L. German, E. Pfluger, and in Russia N.E. Vvedensky, who used the telephone to study the electrical reactions of the nervous system (1884); V. Einthoven, and then A.F. Samoilov accurately recorded short and weak electrical reactions of the nervous system using a string galvanometer; American scientists G. Bishop. J. Erlanger and G. Gasser (1924) introduced electronic amplifiers and oscilloscopes into the practice of neurophysiology. These technical achievements were then used to study the activity of individual neuromotor units (electromyography), to record the total electrical activity of the cerebral cortex (electroencephalography), etc.

2.1.2 Methods of neurophysiology

Methods for studying the human brain are constantly being improved. So, modern methods tomography allows you to see the structure of the human brain without damaging it. According to the principle of one of these studies - the method of magnetic resonance imaging (MRI), the brain is irradiated with an electromagnetic field, using a special magnet for this. Under the action of a magnetic field, the dipoles of brain fluids (for example, water molecules) take its direction. After the removal of the external magnetic field, the dipoles return to their original state, and in this case magnetic signal, which is captured by special sensors. Then this echo is processed using a powerful computer and displayed on the monitor screen using computer graphics methods. Due to the fact that the external magnetic field created by an external magnet can be made flat, such a field as a kind of "surgical knife" can "cut" the brain into separate layers. On the monitor screen, scientists observe a series of successive "sections" of the brain, without causing any harm to it. This method allows you to investigate, for example, malignant brain tumors.

Positron emission tomography (PET) has an even higher resolution. The study is based on the introduction of a positron-emitting short-lived isotope into the cerebral circulation. Data on the distribution of radioactivity in the brain is collected by a computer during a certain scan time and then reconstructed into a three-dimensional image. The method makes it possible to observe foci of excitation in the brain, for example, when thinking through individual words, when they are spoken aloud, which indicates its high resolving capabilities. At the same time, many physiological processes in the human brain proceed much faster than the possibilities that the tomographic method has. In the research of scientists, the financial factor, that is, the cost of the study, is of no small importance.

Physiologists also have various electrophysiological research methods at their disposal. They are also absolutely not dangerous for the human brain and allow you to observe the course of physiological processes in the range from fractions of a millisecond (1 ms = 1/1000 s) to several hours. If tomography is a product of the scientific thought of the 20th century, then electrophysiology has deep historical roots.

In the 18th century, the Italian physician Luigi Galvani noticed that the dissected legs of a frog (now we call such a preparation neuromuscular) shrink when in contact with metal. Galvani made public his remarkable discovery, calling it bioelectricity.

Let's skip a significant section of history and turn to XIX century. By this time, the first physical instruments (string galvanometers) had already appeared, which made it possible to study weak electrical potentials from biological objects. In Manchester (England), G. Cato for the first time placed electrodes (metal wires) on the occipital lobes of the dog's brain and registered fluctuations in the electrical potential when the dog's eyes were illuminated with light. Such fluctuations in the electric potential are now called evoked potentials and are widely used in the study of the human brain. This discovery glorified the name of Cato and has come down to our time, but the contemporaries of the remarkable scientist deeply revered him as the mayor of Manchester, and not as a scientist.

In Russia, similar studies were carried out by I.M. Sechenov: for the first time he managed to register bioelectric oscillations from the medulla oblongata of a frog. Another of our compatriots, professor of Kazan University I. Pravdich-Neminsky studied the bioelectrical oscillations of the dog's brain in various states of the animal - at rest and during arousal. Actually, these were the first electroencephalograms. However, studies conducted at the beginning of the 20th century by the Swedish researcher G. Berger received worldwide recognition. Using already much more advanced instruments, he registered the bioelectric potentials of the human brain, which are now called the electroencephalogram. In these studies, the main rhythm of the biocurrents of the human brain was registered for the first time - sinusoidal oscillations with a frequency of 8-12 Hz, which was called the alpha rhythm. This can be considered the beginning of the modern era of research into the physiology of the human brain.

Modern methods of clinical and experimental electroencephalography have taken a significant step forward thanks to the use of computers. Usually, several dozen cup electrodes are applied to the surface of the scalp during a clinical examination of the patient. Further, these electrodes are connected to a multichannel amplifier. Modern amplifiers are very sensitive and allow recording electrical vibrations from the brain with an amplitude of only a few microvolts (1 μV = 1/1,000,000 V). Further, a sufficiently powerful computer processes the EEG for each channel. A psychophysiologist or doctor, depending on whether the brain of a healthy person or a patient is being studied, is interested in many EEG characteristics that reflect certain aspects of brain activity, for example, EEG rhythms (alpha, beta, theta, etc.), characterizing the level of brain activity. An example is the use of this method in anesthesiology. At present, in all surgical clinics of the world, during operations under anesthesia, along with the electrocardiogram, the EEG is also recorded, the rhythms of which can very accurately indicate the depth of anesthesia and control brain activity. Below we will deal with the application of the EEG method in other cases.

Neurobiological approach to the study of the human nervous system. In theoretical studies of the physiology of the human brain, the study of the central nervous system of animals plays a huge role. This field of knowledge is called neuroscience. The fact is that the brain of modern man is a product of the long evolution of life on Earth. On the path of this evolution, which began on Earth approximately 3-4 billion years ago and continues in our time, Nature moved over many variants of the structure of the central nervous system and its elements. For example, neurons, their processes, and the processes occurring in neurons remain unchanged both in primitive animals (for example, arthropods, fish, amphibians, reptiles, etc.) and in humans. This means that Nature stopped at a successful model of her creation and did not change it for hundreds of millions of years. This has happened to many brain structures. The exception is the cerebral hemispheres. They are unique in the human brain. Therefore, a neurobiologist, having at his disposal a huge number of objects of study, can always study one or another issue of the physiology of the human brain on simpler, cheaper and more accessible objects. Such objects can be invertebrates. For example, one of the classic objects of modern neurophysiology is the cephalopod squid; its nerve fiber (the so-called giant axon), on which classical studies on the physiology of excitable membranes were performed.

In recent years, intravital sections of the brain of newborn rat pups and guinea pigs and even a culture of nervous tissue grown in a laboratory. What questions can neurobiology solve with its methods? First of all - the study of the mechanisms of functioning of individual nerve cells and their processes. For example, cephalopods (squid, cuttlefish) have very thick, giant axons (500-1000 µm in diameter), through which excitation is transmitted from the head ganglion to the muscles of the mantle. Molecular mechanisms of excitation are being investigated at this facility. Many mollusks in the nerve ganglia that replace their brains have very large neurons - up to 1000 microns in diameter. These neurons are a favorite subject for studying ion channels, which are controlled by chemicals to open and close. A number of issues of the transfer of excitation from one neuron to another are being studied at the neuromuscular junction - the synapse (synapse in Greek means contact); these synapses are hundreds of times larger than similar synapses in the mammalian brain. Very complex and not fully understood processes take place here. For example, a nerve impulse at a synapse results in the release of a chemical that causes the excitation to be transmitted to another neuron. The study of these processes and their understanding underlie the entire modern industry for the production of drugs and other drugs. The list of questions that modern neuroscience can address is endless. We will consider some examples below.

To register the bioelectrical activity of neurons and their processes, special techniques are used, which are called microelectrode technology. Microelectrode technique, depending on the objectives of the study, has many features. Two types of microelectrodes are usually used - metal and glass. Metal microelectrodes are often made from tungsten wire with a diameter of 0.3-1 mm. At the first stage, workpieces 10-20 cm long are cut (this is determined by the depth to which the microelectrode will be immersed in the brain of the animal under study). One end of the workpiece is electrolytically ground to a diameter of 1-10 microns. After thorough washing of the surface in special solutions, it is varnished for electrical insulation. The very tip of the electrode remains uninsulated (sometimes a weak current impulse is passed through such a microelectrode in order to further destroy the insulation at the very tip).

To record the activity of single neurons, the microelectrode is fixed in a special manipulator, which allows it to be advanced in the animal's brain with high accuracy. Depending on the objectives of the study, the manipulator can be mounted on the animal's skull or separately. In the first case, these are very miniature devices, which are called micromanipulators. The nature of the recorded bioelectrical activity is determined by the diameter of the microelectrode tip. For example, with a microelectrode tip diameter of no more than 5 µm, action potentials of single neurons can be recorded (in these cases, the microelectrode tip should approach the studied neuron at a distance of about 100 µm). When the diameter of the microelectrode tip is more than 10 μm, the activity of tens and sometimes hundreds of neurons is simultaneously recorded (multiplay activity).

Another widespread type of microelectrodes is made from glass capillaries (tubes). For this purpose, capillaries with a diameter of 1-3 mm are used. Further, on a special device, the so-called forge of microelectrodes, the following operation is performed: the capillary in the middle part is heated to the glass melting temperature and is broken. Depending on the parameters of this procedure (heating temperature, the size of the heating zone, the speed and strength of the gap, etc.), micropipettes are obtained with a tip diameter of up to fractions of a micrometer. In the next step, the micropipette is filled with a salt solution (for example, 2M KCl) and a microelectrode is obtained. The tip of such a microelectrode can be inserted into a neuron (into the body or even into its processes) without severely damaging its membrane and preserving its vital activity.

Another direction in the study of the human brain arose during the Second World War - this is neuropsychology. One of the founders of this approach was Professor of Moscow University A.R. Luria. The method is a combination of psychological examination techniques with physiological examination of a person with brain damage. The results obtained in such studies will be repeatedly cited below.

Methods for studying the human brain are not limited to those described above. In the introduction, the author rather sought to show the modern possibilities of studying the brain of a healthy and sick person, rather than describe all modern methods of research. These methods did not arise from scratch - some of them have a long history, others have become possible only in the age of modern computing tools. While reading the book, the reader will come across other methods of research, the essence of which will be explained in the course of the description.

2.1.3 Modern neurophysiology

At the present stage, the functions of neurophysiology are based on the study of the integrative activity of the nervous system. The study is carried out by means of surface and implanted electrodes, as well as temperature stimuli of the nervous system. Also, the study of the cellular mechanisms of the nervous system, which uses modern microelectrode technology, continues to develop. Microelectrodes are introduced into the neuron and thus receive information about the development of the processes of excitation and inhibition. In addition, a novelty in the study of the human nervous system was the use of electron microscopy, which allowed neurophysiologists to study the ways of encoding and transmitting information in the brain. In some research centers, work is already underway that allows you to model individual neurons and nerve networks. At the present stage, neurophysiology is closely connected with such sciences as neurocybernetics, neurochemistry and neurobionics. Neurophysiological methods (electroencephalography, myography, nystagmography, etc.) are used to diagnose and treat diseases such as stroke, locomotor disorders, epilepsy, multiple sclerosis, as well as rare neuropathological diseases, etc.

2.2 Physiology of the human brain

The human brain is extremely complex. Even now, when we know so much about the brain not only of man, but also of a number of animals, we are apparently still very far from understanding the physiological mechanisms of many mental functions. We can say that these issues are only included in the agenda of modern science. First of all, this concerns such mental processes as thinking, perception of the surrounding world and memory, and many others. At the same time, the main problems that will have to be solved in the third millennium are now clearly defined. What can modern science offer to a person who is interested in how the human brain functions? First of all, the fact that several systems “work” in our brain, at least three. Each of these systems can even be called a separate brain, although in a healthy brain each of them works in close cooperation and interaction. What are these systems? These are the activating brain, the motivational brain, and the cognitive, or cognitive (from Latin cognitio - “knowledge”) brain. As already mentioned, it should not be understood that these three systems, like nesting dolls, are nested one inside the other. Each of them, in addition to its main function, for example, the activating system (the brain), both participates in determining the state of our consciousness, sleep-wake cycles, and is an integral part of the cognitive processes of our brain. Indeed, if a person has a disturbed sleep, then the process of learning and other activities is impossible. Violation of biological motivations may be incompatible with life. These examples can be multiplied, but the main idea is that the human brain is a single organ that provides vital activity and mental functions, however, for convenience of description, we will single out the three blocks indicated above in it.

2.2.1 Cell - the basic unit of nervous tissue

The human brain is made up of huge amount varied cells. The cell is the basic unit of a biological organism. The most simply organized animals may have only one cell. Complex organisms are made up of myriads of cells and are thus multicellular. But in all these cases, the cell remains the unit of the biological organism. Cells of different organisms - from humans to amoeba - are arranged very similarly. The cell is surrounded by a membrane that separates the cytoplasm from the environment. The central place in the cell is occupied by the nucleus, which contains the genetic apparatus that stores the genetic code of the structure of our entire organism. But each cell uses only a small part of this code in its life activity. In addition to the nucleus, there are many other organelles (particles) in the cytoplasm. Among them, one of the most important is the endoplasmic reticulum, composed of numerous membranes on which many ribosomes are attached. On ribosomes, protein molecules are assembled from individual amino acids according to the program of the genetic code. Part of the endoplasmic reticulum is represented by the Golgi apparatus. Thus, the endoplasmic reticulum is a kind of factory, equipped with everything necessary for the production of protein molecules. Other very important organelles of the cell are mitochondria, thanks to the activity of which the necessary amount of ATP (adenosine triphosphate) - the universal "fuel" of the cell - is constantly maintained in the cell.

The neuron, which is the structural basic unit of the nervous tissue, has all the structures listed above. At the same time, the neuron is designed by nature to process information and therefore has certain features that biologists call specialization. The most general plan of the cell structure was described above. In fact, any cell in our body is adapted by nature to perform a strictly defined, specialized function. For example, the cells that make up the heart muscle have the ability to contract, and the skin cells protect our body from the penetration of microorganisms.

Neuron

The neuron is the main cell of the central nervous system. The forms of neurons are extremely diverse, but the main parts are the same for all types of neurons. The neuron consists of the following parts: soma (body) and numerous branched processes. ka Each neuron has two types of processes: an axon, along which excitation is transmitted from a neuron to another neuron, and numerous dendrites (from the Greek for "tree"), on which axons from other neurons end in synapses (from the Greek. contact). The neuron conducts excitation only from the dendrite to the axon.

The main property of a neuron is the ability to be excited (generate an electrical impulse) and transmit (conduct) this excitation to other neurons, muscle, glandular and other cells.

The neurons of different parts of the brain perform a very diverse job, and in accordance with this, the shape of neurons from different parts the brain is also diverse. Neurons located at the output of a neural network of some structure have a long axon, along which excitation leaves this brain structure.

For example, the neurons of the motor cortex of the brain, the so-called pyramids of Betz (named after the Kyiv anatomist B. Betz, who first described them in the middle of the 19th century), have an axon of about 1 m in a person, it connects the motor cortex of the cerebral hemispheres with segments of the spinal cord. This axon transmits "motor commands", such as "wiggle your toes." How is a neuron fired? The main role in this process belongs to the membrane, which separates the cytoplasm of the cell from the environment. The membrane of a neuron, like any other cell, is very complex. Basically, all known biological membranes have a uniform structure: a layer of protein molecules, then a layer of lipid molecules and another layer of protein molecules. This whole design resembles two sandwiches folded with butter to each other. The thickness of such a membrane is 7-11 nm. A variety of particles are embedded in such a membrane. Some of them are protein particles and penetrate the membrane through (integral proteins), they form passage points for a number of ions: sodium, potassium, calcium, chlorine. These are the so-called ion channels. Other particles are attached to the outer surface of the membrane and consist not only of protein molecules, but also of polysaccharides. These are receptors for molecules of biologically active substances, such as mediators, hormones, etc. Often, in addition to the site for binding a specific molecule, the receptor also includes an ion channel.

Membrane ion channels play the main role in excitation of the neuron. These channels are of two types: some work constantly and pump out sodium ions from the neuron and pump potassium ions into the cytoplasm. Thanks to the work of these channels (they are also called pumping channels or ion pump), which constantly consume energy, a difference in ion concentrations is created in the cell: inside the cell, the concentration of potassium ions is about 30 times higher than their concentration outside the cell, while the concentration of sodium ions in the cell is very small - about 50 times less than outside the cell. The property of the membrane to constantly maintain the difference in ionic concentrations between the cytoplasm and the environment is characteristic not only for the nervous, but also for any cell of the body. As a result, a potential arises between the cytoplasm and the external environment on the cell membrane: the cytoplasm of the cell is negatively charged by a value of about 70 mV relative to the external environment of the cell. This potential can be measured in the laboratory with a glass electrode, if a very thin (less than 1 μm) glass tube filled with a salt solution is introduced into the cell. Glass in such an electrode plays the role of a good insulator, and the salt solution acts as a conductor. The electrode is connected to an amplifier of electrical signals and this potential is recorded on the oscilloscope screen. It turns out that a potential of the order of -70 mV is preserved in the absence of sodium ions, but depends on the concentration of potassium ions. In other words, only potassium ions participate in the creation of this potential, in connection with which this potential was called the “potassium resting potential”, or simply “resting potential”. Thus, this is the potential of any resting cell in our body, including a neuron.

Glia - morphology and function

The human brain is made up of hundreds of billions of cells, with nerve cells (neurons) not making up the majority. Most of the volume of the nervous tissue (up to 9/10 in some areas of the brain) is occupied by glial cells. The fact is that a neuron performs a gigantic very delicate and difficult work in our body, for which it is necessary to free such a cell from everyday activities related to nutrition, removal of toxins, protection from mechanical damage, etc. - this is provided by other, serving cells, i.e. glial cells (Fig. 3). Three types of glial cells are distinguished in the brain: microglia, oligodendroglia and astroglia, each of which provides only its intended function. Microglial cells are involved in the formation of the meninges, oligodendroglia - in the formation of membranes (mylein sheaths) around individual processes of nerve cells. Myelin sheaths around peripheral nerve fibers are formed by special putrefactive cells - Schwann cells. Astrocytes are located around neurons, providing them mechanical protection, and in addition, they deliver nutrients to the neuron and remove toxins. Glial cells also provide electrical isolation of individual neurons from the effects of other neurons. An important feature of glial cells is that, unlike neurons, they retain the ability to divide throughout their lives. This division in some cases leads to tumor diseases of the human brain. The nerve cell is so specialized that it has lost the ability to divide. Thus, the neurons of our brain, once formed from precursor cells (neuroblasts), live with us all our lives. On this long journey, we only lose the neurons of our brain.

Excitation of a neuron

A neuron, unlike other cells, is capable of excitation. The excitation of a neuron is understood as the generation of sweat by the neuron. action ncial. The main role in excitation belongs to another type of ion channels, upon opening of which sodium ions rush into the cell. Recall that due to the constant operation of pumping channels, the concentration of sodium ions outside the cell is about 50 times greater than in the cell, therefore, when sodium channels are opened, sodium ions rush into the cell, and potassium ions begin to leave the cell through open potassium channels. Each type of ion - sodium and potassium - has its own type of ion channel. The movement of ions through these channels occurs along concentration gradients, i.e. from a place of high concentration to a place of lower concentration.

In a resting neuron, the sodium channels of the membrane are closed and, as already described above, a resting potential of the order of -70 mV is recorded on the membrane (negativity in the cytoplasm). If the membrane potential is depolarized (reduces membrane polarization) by about 10 mV, the sodium ion channel opens.

Indeed, there is a kind of shutter in the channel, which reacts to the potential of the membrane, opening this channel when the potential reaches a certain value. Such a channel is called voltage-dependent. As soon as the channel opens, sodium ions rush into the cytoplasm of the neuron from the intercellular medium, which are about 50 times more there than in the cytoplasm. This movement of ions is a consequence of a simple physical law: ions move along a concentration gradient. Thus, sodium ions enter the neuron, they are positively charged. In other words, an incoming current of sodium ions will flow through the membrane, which will shift the membrane potential towards depolarization, i.e., reduce the polarization of the membrane. The more sodium ions enter the cytoplasm of the neuron, the more its membrane depolarizes.

The potential across the membrane will increase, opening all large quantity sodium channels. But this potential will not grow indefinitely, but only until it becomes equal to approximately +55 mV. This potential corresponds to the concentrations of sodium ions present in the neuron and outside it, therefore it is called the sodium equilibrium potential. Recall that at rest the membrane had a potential of -70 mV, then the absolute amplitude of the potential will be about 125 mV. We say “about”, “approximately” because this potential may differ slightly for cells of different sizes and types, which is associated with the shape of these cells (for example, the number of processes), as well as with the characteristics of their membranes.

All of the above can be formally described as follows. At rest, the cell behaves like a "potassium electrode", and when excited, it behaves like a "sodium electrode". However, after the potential on the membrane reaches its maximum value of +55 mV, the sodium ion channel from the side facing the cytoplasm is clogged with a special protein molecule. This is the so-called "sodium inactivation", it occurs after about 0.5-1 ms and does not depend on the potential on the membrane. The membrane becomes impermeable to sodium ions. In order for the membrane potential to return to its original state, the state of rest, it is necessary that a current of positive particles leave the cell. Such particles in neurons are potassium ions. They begin to exit through open potassium channels. Recall that potassium ions accumulate in a cell at rest, so when potassium channels open, these ions leave the neuron, returning the membrane potential to its original level (resting level). As a result of these processes, the neuron membrane returns to a state of rest (-70 mV) and the neuron prepares for the next act of excitation. Thus, the expression of excitation of a neuron is the generation of an action potential on the membrane of the neuron. Its duration in nerve cells is about 1/1000 s (1 ms). Similar action potentials can also occur in other cells, the purpose of which is to be excited and transmit this excitation to other cells. For example, the heart muscle contains special muscle fibers that ensure the uninterrupted operation of the heart in automatic mode. Action potentials are also generated in these cells. However, they have a tightened, almost flat top, and the duration of such an action potential can be delayed up to several hundred milliseconds (compare with 1 ms for a neuron). This nature of the action potential of the muscle cell of the heart is physiologically justified, since the excitation of the heart muscle must be prolonged so that the blood has time to leave the ventricle. What is the reason for such a prolonged action potential in this type of cell? It turned out that sodium ion channels in the membrane of these cells do not close as quickly as in neurons, i.e., sodium inactivation is delayed.

...

Neurophysiology of motivations

In the body, under the influence of a certain physiological need, an emotionally colored state develops - motivation. An effective method for studying the neurophysiological mechanisms of various motivations is the self-stimulation method proposed by the American scientist J. Olds (1953).

Special metal electrodes are implanted into various parts of the rat's brain. If, by accidentally pressing the lever, the animal produces electrical stimulation of its own brain through electrodes implanted in its various parts, then, depending on the localization of the current application, a different pattern of behavior is observed. When electrodes are located in some structures of the brain, the animal tends to re-stimulation, in others it avoids it, and in still others it remains indifferent. On fig. 4.12 shows the scheme of the experiment for obtaining a self-stimulation reaction in a rat. The points of the brain willingly stimulated by the animal - the positive zones - are located mainly in the medial region of the brain, extending from the nuclei of the amygdala through the hypothalamus to the tegmentum of the midbrain (Fig. 4.13). In the region of the tegmentum of the midbrain, posterior hypothalamus (rostral mammillary bodies) and septum, the frequency of self-stimulation, for example, in rats, was the highest and reached 7000 per hour. Some animals pressed the lever to the point of exhaustion, refusing food and water.

Brain points associated with avoidance of stimulation (negative zones) were located predominantly in the dorsal part of the midbrain and the lateral part of the posterior hypothalamus. In the rat brain, points of positive self-stimulation are approximately 35%, negative - 5% and neutral - 60% (see Fig. 4.13). An extensive system of positive reinforcement includes a number of subsystems corresponding to the main types of motivation - food, sexual, etc. In some animals, hunger increases, and saturation reduces the frequency of self-stimulation through electrodes in the hypothalamus. In males, after castration, the frequency of self-stimulation of certain points of the brain decreases. The introduction of testosterone restores the original sensitivity to the current. In those points of the brain where hunger increases the frequency of self-stimulation, the introduced androgens reduced it, and vice versa.

Artificially induced motivation is no less effective than natural motivations, corresponding to the basic types of physiological needs, such as the consumption of food, water, etc. For the sake of "pleasant" brain stimulation, animals even endure strong pain irritation, heading towards the lever through the electrified floor of the chamber. At the same time, the question of the correspondence between the mechanisms of positive reinforcement during self-stimulation and the mechanisms of natural motivations remains debatable. However, it is essential that at a certain intensity of the current passed through the points of self-stimulation, it is possible to induce such reactions as eating, drinking, mating, and other specific types of behavior. The localization of these points, as a rule, coincides with the centers related to the control of various biological types of motivations. In addition, self-stimulation can provide the necessary motivation for animal learning. It is not known what the animal feels during self-stimulation. Observations of sick people with electrodes chronically implanted in the brain for the purpose of diagnosis and treatment show that in a number of cases they experience self-stimulation reactions, which they often perceive as stress relief, relief, etc. However, in some patients, the desire for self-stimulation is associated with a sense of pleasure.

Our body is constantly exposed to adverse effects, which may be of a physical nature. For example, severe cooling or overheating of the body, blood loss and various injuries. Adverse effects on the body can be deprivation of necessary needs, such as hunger, thirst. Finally, these impacts can be directed to the psyche, for example, the loss of close relatives and friends, being present during violence, etc. It turns out that despite the difference in such adverse effects, they cause fairly uniform changes in the body, which are called stress.

The concept of stress was formulated by the Canadian scientist Hans Selye in 1936. According to these ideas, under the influence of various harmful agents, stressors (cold, toxic substances in sublethal doses, excessive muscle load, blood loss, etc.), a characteristic syndrome arises that does not depend on the nature of the cause that caused it and is called stress. In its development, the syndrome goes through three stages. In the first - stages of anxiety within 6-48 hours after the onset of damage, a rapid decrease in the thymus, spleen, liver, lymph glands is observed, the composition of the blood changes (eosinophils disappear), ulcers appear in the mucous membrane of the gastrointestinal tract. In the second stage - resistance(resistance) - the secretion of somatotropic and gonadotropic hormones from the hypothalamus stops, and the adrenal glands increase significantly. Depending on the strength of the impact at this stage, either an increase in the body's resistance and restoration of the initial state occurs, or the body loses its resistance, which leads to the third stage - stages of exhaustion. Selye considered stress as a generalized non-specific effort of the body to adapt to new conditions and therefore called it (general adaptation syndrome).

The stereotypical nature of the syndrome is determined by a number of nervous and neuroendocrine mechanisms. The most typical manifestation of the syndrome develops as a result of the release of adrenocorticotropic hormone (ACTH) from the pituitary gland, which acts on the adrenal glands. An important role in the development of manifestations of stress is played by somatotropic hormone, which weakens the effect of ACTH. Ulceration of the mucous membrane of the intestines and stomach during stress is of a purely nervous nature. This symptom can be induced in an animal experiment by chronic mechanical or electrical stimulation of the anterior hypothalamus.

Questions

1. Functions of the nervous autonomic system.

2. Sympathetic and parasympathetic parts of the nervous system: the structure of reflex arcs, mediators, the nature of the action.

3. Nervous control of the hormonal system.

4. Basic elements of a functional system.

5. Biological motivations for the consumption of food, water, rage, reproduction; brain mechanisms.

Literature

Neuroendocrinology/Under, ed. A. L. Polenova. SPb., 1993.

Nozdrachev A. D. Physiology of the nervous autonomic system. M., 1983.

Potemkin V.V. Endocrinology. M., 1986.

Simonov P.V. Lectures on the work of the brain. M.: IP RAN, 1998.

Shulgovsky V.V. Physiology of the central nervous system. M.: Publishing House of Moscow. un-ta, 1997.

The book presents modern ideas about the function of cells and nervous regulation, as well as the complex hierarchical regulation of the main activities of the body. The book is based on courses of lectures given by the author over a number of years at Moscow State University. M. V. Lomonosov and the Humanitarian Institute.
For students, graduate students of pedagogical and humanitarian universities.

Advances in the study of the human brain at the present time.
There is a principle in biology that can be formulated as the principle of the unity of structure and function. For example, the function of the heart (pushing blood through the vessels of our body) is completely determined by the structure of both the ventricles of the heart, and valves, and other things. The same principle applies to the brain. Therefore, questions of the morphology and anatomy of the brain have always been considered very important in the study of the activity of this most complex organ.

Anatomy and morphology of the brain is an ancient science. The names of ancient anatomists - Willisius, Sylvia, Roland and many others - are preserved in the names of brain structures. The human brain consists of the cerebral hemispheres - the highest center of his mental activity (see Appendix 1). This is the largest part of our brain. The diencephalon consists of two unequal parts: the thalamus, which is a kind of distributor (collector) of signals sent to areas of the cortex, including signals from the organs of vision, hearing, etc., and the hypothalamus (located under the thalamus), which "manages" the our body with vegetative (providing the "plant" life of our body) functions. Thanks to the hypothalamus, the growth and maturation (including sexual) of our body occurs, the constancy of the internal environment is maintained, for example, maintaining body temperature, removing toxins from the body, consuming food and water, and many other processes.

Finally, the back of the brain is occupied by the brain stem, which, in turn, consists of a number of departments: the midbrain, the pons, and the medulla oblongata. These structures are involved in the implementation of the most complex functions of the body - maintaining the level of blood pressure, breathing, setting the gaze, regulating the sleep-wake cycle, in the manifestation of orienting reactions, and many others. 10 pairs of cranial nerves emerge from the brain stem, thanks to the activity of which many functions are carried out: regulation of the functions of the heart and respiration, activity of the facial muscles, perception of signals from the external world and the internal environment. The entire core of the brain stem is occupied by the reticular (mesh) formation. The activity of this structure determines the sleep-wake cycle, violation of its integrity leads to gross violations of consciousness, which doctors call coma. Above the bridge is the cerebellum, or small brain.

TABLE OF CONTENTS
INTRODUCTION
WHY DOES A PSYCHOLOGIST NEED TO KNOW THE PHYSIOLOGY OF THE BRAIN?
CURRENT SUCCESS IN HUMAN BRAIN RESEARCH
NEUROBIOLOGICAL APPROACH TO STUDY OF THE HUMAN NERVOUS SYSTEM
PART I PHYSIOLOGY OF THE HUMAN BRAIN
CHAPTER 1 DEVELOPMENT OF THE HUMAN NERVOUS SYSTEM
BRAIN FORMATION FROM FERTILIZATION TO BIRTH
CHAPTER 2. CELL - THE BASIC UNIT OF NERVOUS TISSUE
GLIA - MORPHOLOGY AND FUNCTION
NEURON
NEURON EXCITATION
CONDUCTING EXCITATION
SYNAPSE
NERVOUS SYSTEM MEDIATORS
OPIATE RECEPTORS AND BRAIN OPIOIDS
CHAPTER 3. ACTIVATED SYSTEMS OF THE BRAIN
PHYSIOLOGICAL MECHANISMS OF SLEEP
MENTAL ACTIVITY IN SLEEP
CHAPTER 4
PERIPHERAL PART OF THE AUTONOMIC NERVOUS SYSTEM
VEGETATIVE CENTERS OF THE BRAIN STEM
LIMBIC SYSTEM OF THE BRAIN
PHYSIOLOGY OF THE HYPOTHALAMUS
CONTROL OF THE FUNCTIONS OF THE ENDOCRINE SYSTEM
BODY TEMPERATURE REGULATION
CONTROL OF WATER BALANCE IN THE BODY
REGULATION OF EATING BEHAVIOR
REGULATION OF SEXUAL BEHAVIOR
NERVOUS MECHANISMS OF FEAR AND RAGE
PHYSIOLOGY OF THE TONGAL
PHYSIOLOGY OF THE HIPPOCAMPUS
NEUROPHYSIOLOGY OF MOTIVATIONS
STRESS
PART II. COGNITIVE BRAIN
CHAPTER 5. PHYSIOLOGY OF MOVEMENTS
REFLECTOR LEVEL OF MOVEMENT ORGANIZATION
PHYSIOLOGY OF THE CEREbellum
NEUROPHYSIOLOGY OF THE STRAIARY SYSTEM
DOWNLOAD ENGINE CONTROL SYSTEMS
CHAPTER 6. PHYSIOLOGY OF SENSORY SYSTEMS
NEUROPHYSIOLOGY OF THE VISUAL SYSTEM
NEUROPHYSIOLOGY OF THE AUDIOUS SYSTEM
NEUROPHYSIOLOGY OF THE SOMATOSENSORY SYSTEM
NEUROPHYSIOLOGY OF SENSORY WAYS OF THE SPINAL CORD
PHYSIOLOGY OF THE TRIGENETIC NEVER
NEUROPHYSIOLOGY OF THE OLFACTORY SYSTEM
NEUROPHYSIOLOGY OF TASTE
CHAPTER 7. HIGHER FUNCTIONS OF THE NERVOUS SYSTEM
ASYMMETRY OF THE HEMISPHERES OF THE HUMAN BRAIN
TEMPORAL SECTIONS OF THE BRAIN AND ORGANIZATION OF THE HEARING
PERCEPTIONS
Occipital regions of the brain and visual perception
PARTICIPATION OF THE CORTEX IN THE ORGANIZATION OF VISUAL SPATIAL SYNTHESIS
FRONTAL BRAIN AND REGULATION OF HUMAN MENTAL ACTIVITY
CONCLUSION
APPS
Dictionary.

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