Neurons and nervous tissue. Functions of neurons: how they work and what task they perform

Incredible facts

The human body is incredible complex and confusing a system that still confuses doctors and researchers, despite thousands of years of medical knowledge.

As a result, bizarre and sometimes incredible facts our body.

The brain is the most complex and least understood part human anatomy. We may not know much about him, but here are a few very interesting facts, which known.

Speed ​​of impulses in the brain

Nerve impulses travel through the brain at a speed 273 km per hour.

Have you ever wondered why you react so quickly to what is happening around you? Why does a wounded finger hurt immediately? This is due to the extremely rapid movement of nerve impulses from the brain to parts of your body and vice versa. As a result, the reaction speed of nerve impulses is comparable to the speed of a powerful luxury sports car.

Brain Energy

The brain produces energy equivalent to a light bulb 10 Watt. Cartoons where characters have a light bulb hanging over their heads while they are thinking are not too far from the truth. Your brain generates as much energy as a small light bulb, even When you sleep.

Meanwhile, the brain is the organ with the highest energy consumption. It takes about 20% energy, it accounts for 2% of the total body weight. Much of this energy is spent exchanging information between neurons and between neurons and astrocytes (a type of cell).

Brain memory

Human brain cells can store 5 times more information than the British or other encyclopedias.

Scientists have yet to find out final numbers, however, the brain capacity in electronic terms is estimated to be about 1000 terabytes.

For example, the UK National Archive, containing historical records for 900 years, occupies only 70 terabytes. This makes human memory impressively capacious.

Oxygen in the brain

Your brain uses 20% oxygen, which you breathe. Despite the small mass of the brain, it consumes more oxygen than any other organ in the human body.

This makes the brain very sensitive to damage associated with oxygen deprivation. That's why he likes it when you breathe deeply.

If the flow of oxygen to the brain is increased, those areas of the brain that did not function when weak will begin to become active. blood flow and the process of aging and cell death will slow down.

Interesting fact! Carotid arteries have ramifications in the smallest vessels inside the skull, forming an intricate and amazing network of capillaries. These are very thin blood tunnels that provide blood access to the smallest areas of the brain, providing required quantity neurons and oxygen.

Brain function during sleep

The brain is more active at night, than during the day. Logically, we can assume that we carry out thought processes, complex calculations and tasks during the working day, which would require more brain activity than, say, lying in bed.

It turns out the opposite is also true. As soon as you fall asleep, the brain continues to work. Scientists do not yet fully know why this is so, but for all dreams We should be grateful to this organ.

Interesting fact! IN early childhood there is no difference between sleep and wakefulness. This is explained by the place of thinking in the brain. It is in childhood that almost all thought processes occur in the right hemisphere. A child experiences the world through images. Therefore, a child’s memories are similar to dreams in their structure.

A mature child is taught ready-made and definite concepts, which “clog” our brain. Therefore, asymmetry of our brain occurs. The left hemisphere is overloaded during daytime work. The situation seems to even out during sleep, when left hemisphere“falls asleep,” and the right begins to actively act, immersing us in the world of imaginative thinking.

Brain function during daydreaming

Scientists say that the higher the I.Q. a person, the more he dreams.

This of course may be true, but do not take such a statement as a lack of thoughts if you cannot remember your dreams. Most of us don't remember many dreams. After all, the time of most of the dreams that we think about is 2-3 seconds, and this is barely enough for the brain to register them.

Interesting fact! Scientists conducted an experiment that found that the brain is much more active in humans, when he dreams rather than focusing on monotonous work.

At the moment the dreaming process begins, most parts of the brain begin to work intensely. Therefore, we can conclude that dreams help in resolving all important problems.

Number of neurons in the brain

The number of neurons in the brain continues to grow throughout human life.

For many years, scientists and doctors believed that the brain and nerve tissue cannot grow or repair. But it turned out that the brain works in the same way as the tissues of many other parts of the body. Therefore the number of neurons can grow constantly.

For your information! Neurons are the basis any nervous system. These are special cells in which tree-like processes diverge in all directions, coming into contact with neighboring cells that have the same processes. All this forms a huge chemical and electrical network, which is our brain.

It is neurons that allow the brain to perform various actions much more efficiently and quickly than any created machine.

The brain doesn't feel pain

The brain itself cannot feel pain. While the brain is the center for processing pain, when you cut your finger or get burned, it doesn't have pain receptors and doesn't feel pain.

However, the brain is surrounded by many tissues, nerves and blood vessels which are very susceptible to pain and can give you headaches.

However, headaches have different kinds, and the exact causes of many remain unclear.

Human brain and water

80% the brain consists of water. Your brain is not the solid gray mass you see on TV. It is a soft and pink tissue due to the blood pulsating there and high content water.

So, when you feel thirsty, it is also because brain requires water.

Interesting fact! The average human brain weighs 1.4 kg and is extremely sensitive to water loss. If the brain is dehydrated for a long time, its proper existence will cease.

The nervous system seems to be the most complex part human body. It includes about 85 billion nerve and glial cells. To date, scientists have been able to study only 5% of neurons. The other 95% still remains a mystery, so numerous studies are being conducted on these components of the human brain.

Let's consider how the human brain works, namely its cellular structure.

The structure of a neuron consists of 3 main components:

1. Cell body

This part of the nerve cell is key, which includes cytoplasm and nuclei, which together create protoplasm, on the surface of which a membrane boundary is formed, consisting of two layers of lipids. On the membrane surface there are proteins in the form of globules.

Nerve cells of the cortex consist of bodies containing a nucleus, as well as a number of organelles, including an intensively and efficiently developing scattering area of ​​​​a rough shape, which has active ribosomes.

2. Dendrites and axon

The axon appears to be a long process that effectively adapts to exciting processes from the human body.

Dendrites have a completely different anatomical structure. Their main difference from an axon is that they have a significantly shorter length, and are also characterized by the presence of abnormally developed processes that perform the functions of the main section. In this area, inhibitory synapses begin to appear, due to which there is the ability to directly influence the neuron itself.

A significant portion of neurons consists largely of dendrites, with only one axon. One nerve cell has many connections with other cells. In some cases, the number of these connections exceeds 25,000.

The synapse is the place where it is formed contact process between two cells. The main function is the transmission of impulses between different cells, while the frequency of the signal may vary depending on the speed and types of transmission of this signal.

As a rule, for the excitatory process of a nerve cell to begin, several excitatory synapses can act as stimuli.

What is the human triple brain?

Back in 1962, neuroscientist Paul MacLean identified three human brains, namely:

1. Reptilian

This reptilian type The human brain has existed for more than 100 million years. It has a significant impact on human behavioral qualities. His main function is the control of basic behavior, which includes functions such as:

• Reproduction based on human instincts
• Aggression
• Desire to control everything
• Follow certain patterns
• imitate, deceive
• Fight for influence over others

Also, the human reptilian brain is characterized by such features as composure towards others, lack of empathy, complete indifference to the consequences of one’s actions in relation to others. Also, this type is not able to recognize an imaginary threat with real danger. As a result, in some situations, given brain completely subjugates the human mind and body.

1. Emotional (limbic system)

It appears to be the brain of a mammal, about 50 million years old.

Responsible for such functional features of an individual as:

• Survival, self-preservation and self-defense
• Manages social behavior, including maternal care and education
• Participates in the regulation of organ functions, smell, instinctive behavior, memory, sleep and wakefulness and a number of others

This brain is almost completely identical to the brain of animals.

1. Visual

It is the brain that performs the functions of our thinking. In other words, it is the rational mind. It is the youngest structure, whose age does not exceed 3 million years.

It appears to be what we call reason, which includes such abilities as;

• reflect
• Conduct inferences
• Ability to analyze

It is distinguished by the presence of spatial thinking, where characteristic visual images arise.

Classification of neurons

Today, there are a number of classifications of neuron cells. One of the common classifications of neurons is distinguished by the number of processes and the location of their localization, namely:

1. Multipolar. These cells are characterized by a large accumulation in the central nervous system. They appear with one axon and several dendrites.
2. Bipolar. They are characterized by one axon and one dendrite and are located in the retina, olfactory tissue, as well as in the auditory and vestibular centers.

Also, depending on the functions they perform, neurons are divided into 3 large groups:

1. Afferent

They are responsible for the process of transmitting signals from receptors to the central nervous system. Differ as:

• Primary. The primary ones are located in the spinal nuclei, which bind to receptors.
• Secondary. They are located in the visual thalamus and perform the functions of transmitting signals to the overlying sections. This type of cell does not communicate with receptors, but receives signals from neurocyte cells.

2. Efferent or motor

This type forms the transmission of impulse to other centers and organs of the human body. For example, the neurons of the motor zone of the cerebral hemispheres are pyramidal, which transmit the signal motor neurons spinal region. The key feature of motor efferent neurons is the presence of axons of considerable length, with high speed transmitting the excitation signal.

Efferent nerve cells different departments cerebral cortex connect these departments with each other. These neural connections of the brain provide relationships within and between the hemispheres, therefore, which are responsible for the functioning of the brain in the process of learning, object recognition, fatigue, etc.

3. Intercalary or associative

This type carries out interaction between neurons, and also processes data that was transmitted from sensitive cells and then transmit it to other intercalary or motor nerve cells. These cells appear to be smaller in size compared to afferent and efferent cells. The axons are small in length, but the network of dendrites is quite extensive.

Experts have concluded that the direct nerve cells that are localized in the brain are associative neurons of the brain, and the rest regulate the activity of the brain outside of itself.

Do nerve cells recover?

Modern science pays enough attention to the processes of death and restoration of nerve cells. The entire human body has the ability to recover, but do the nerve cells of the brain have this ability?

Even during the process of conception, the body adjusts to the death of nerve cells.

A number of scientists claim that the number of cells wiped off is about 1% per year. Based on this statement, it turns out that the brain would have already worn out to the point of losing the ability to do basic things. However, this process does not occur, and the brain continues to function until death.

Each tissue of the body independently restores itself by dividing “living” cells. However, after a series of studies of the nerve cell, people found that the cell does not divide. It is argued that new brain cells are formed as a result of neurogenesis, which starts in the prenatal period and continues throughout life.

Neurogenesis is the synthesis of new neurons from precursors - stem cells, which subsequently differentiate and form into mature neurons.

This process was first described in 1960, but at that time there was nothing to support this process.

Further research confirmed that neurogenesis may occur in specific brain regions. One such area is the space around the cerebral ventricles. The second area includes the hippocampus, which is located directly next to the ventricles. The hippocampus performs the functions of our memory, thinking and emotions.

As a result, the ability to remember and think is formed in the process of life under the influence various factors. As can be noted from the above, our brain, the determination of the structures of which, although only 5% has been completed, still stands out a number of facts that confirm the ability of nerve cells to recover.

Conclusion

Do not forget that for the full functioning of nerve cells, you should know how to improve the neural connections of the brain. Many experts note that the main guarantee of healthy neurons is healthy eating and lifestyle, and only then can additional pharmacological support be used.

Organize your sleep, give up alcohol and smoking, and in the end your nerve cells will thank you.

Each structure in the human body consists of specific tissues inherent to the organ or system. In nervous tissue - neuron (neurocyte, nerve, neuron, nerve fiber). What are brain neurons? This is a structural and functional unit of nervous tissue that is part of the brain. In addition to the anatomical definition of a neuron, there is also a functional one - it is a cell excited by electrical impulses, capable of processing, storing and transmitting information to other neurons using chemical and electrical signals.

The structure of a nerve cell is not as complex as that of specific cells of other tissues; it also determines its function. Neurocyte consists of a body (another name is soma), and processes - axon and dendrite. Each element of a neuron performs its own function. The soma is surrounded by a layer of fatty tissue, allowing only fat-soluble substances to pass through. Inside the body there is a nucleus and other organelles: ribosomes, endoplasmic reticulum and others.

In addition to the neurons themselves, the brain is dominated by next cells, namely: glial cells. They are often called brain glue for their function: glia serve as a support function for neurons, providing an environment for them. Glial tissue provides nerve tissue with the ability to regenerate, nourish, and assist in the creation of nerve impulses.

The number of neurons in the brain has always interested researchers in the field of neurophysiology. Thus, the number of nerve cells varied from 14 billion to 100. Latest research Brazilian experts found that the number of neurons averages 86 billion cells.

Processes

The tools in the hands of a neuron are the processes, thanks to which the neuron is able to perform its function as a transmitter and storer of information. It is the processes that form a wide nerve network, which allows human psyche reveal itself in all its glory. There is a myth that a person’s mental abilities depend on the number of neurons or on the weight of the brain, but this is not so: those people whose fields and subfields of the brain are highly developed (several times more) become geniuses. Due to this, fields responsible for certain functions will be able to perform these functions more creatively and quickly.

Axon

An axon is a long extension of a neuron that transmits nerve impulses from the nerve soma to other similar cells or organs innervated by a certain part of the nerve column. Nature has endowed vertebrates with a bonus - myelin fiber, the structure of which contains Schwann cells, between which there are small empty areas - nodes of Ranvier. Along them, like on a ladder, nerve impulses jump from one area to another. This structure makes it possible to speed up the transmission of information several times (up to about 100 meters per second). The speed of movement of an electrical impulse along a fiber that does not have myelin averages 2-3 meters per second.

Dendrites

Another type of nerve cell extension is dendrites. Unlike the long and solid axon, the dendrite is a short and branched structure. This process is not involved in transmitting information, but only in receiving it. Thus, excitation reaches the neuron body using short dendritic branches. The complexity of information that a dendrite is capable of receiving is determined by its synapses (specific nerve receptors), namely its surface diameter. Dendrites, thanks a huge number their spines are capable of establishing hundreds of thousands of contacts with other cells.

Metabolism in a neuron

A distinctive feature of nerve cells is their metabolism. Metabolism in the neurocyte is distinguished by its high speed and predominance of aerobic (oxygen-based) processes. This feature of the cell is explained by the fact that the work of the brain is extremely energy-intensive, and its need for oxygen is great. Although the brain weighs only 2% of the body's weight, its oxygen consumption is approximately 46 ml/min, which is 25% of the body's total consumption.

The main source of energy for brain tissue, besides oxygen, is glucose, where it undergoes complex biochemical transformations. Ultimately released from sugar compounds a large number of energy. Thus, the question of how to improve neural connections in the brain can be answered: eat foods containing glucose compounds.

Functions of a neuron

Despite its relatively simple structure, the neuron has many functions, the main ones of which are the following:

• perception of irritation;
• stimulus processing;
• impulse transmission;
• formation of a response.

Functionally, neurons are divided into three groups:

Afferent(sensitive or sensory). Neurons of this group perceive, process and send electrical impulses to the central nervous system. Such cells are anatomically located outside the central nervous system, but in spinal neuronal clusters (ganglia), or the same clusters of cranial nerves.

Intermediaries(also these neurons, which do not extend beyond the spinal cord and brain, are called intercalary). The purpose of these cells is to ensure contact between neurocytes. They are located in all layers of the nervous system.

Efferent(motor, motor). This category of nerve cells is responsible for transmitting chemical impulses to the innervated executive organs, ensuring their performance and setting them functional state.

In addition, another group is functionally distinguished in the nervous system - inhibitory nerves (responsible for inhibiting cell excitation). Such cells resist the propagation of electrical potential.

Classification of neurons

Nerve cells are diverse as such, so neurons can be classified based on their different parameters and attributes, namely:

• Body shape. IN different departments neurocytes are located in the brain different shapes soms:
  • star-shaped;
  • fusiform;
  • pyramidal (Betz cells).
• By the number of shoots:
  • unipolar: have one process;
  • bipolar: there are two processes on the body;
  • multipolar: three or more processes are located on the soma of such cells.
• Contact features of the neuron surface:
  • axo-somatic. In this case, the axon contacts the soma of the neighboring cell of the nervous tissue;
  • axo-dendritic. This type of contact involves the connection of an axon and a dendrite;
  • axo-axonal. The axon of one neuron has connections with the axon of another nerve cell.

Types of neurons

In order to carry out conscious movements, it is necessary that the impulse formed in the motor convolutions of the brain can reach the necessary muscles. Thus, the following types of neurons are distinguished: central motor neuron and peripheral motor neuron.

The first type of nerve cells originates from the anterior central gyrus, located in front of the largest sulcus of the brain - namely, from Betz's pyramidal cells. Next, the axons of the central neuron deepen into the hemispheres and pass through the internal capsule of the brain.

Peripheral motor neurocytes are formed by motor neurons of the anterior horns spinal cord. Their axons reach various formations, such as plexuses, spinal nerve clusters, and, most importantly, the performing muscles.

Development and growth of neurons

A nerve cell originates from a precursor cell. As they develop, axons begin to grow first; dendrites mature somewhat later. At the end of the evolution of the neurocyte process, a small compaction forms at the cell soma irregular shape. This formation is called a growth cone. It contains mitochondria, neurofilaments and tubules. The cell's receptor systems gradually mature and the synaptic areas of the neurocyte expand.

Pathways

The nervous system has its spheres of influence throughout the body. Conductive fibers are used to neural regulation systems, organs and tissues. The brain, thanks to a wide system of pathways, completely controls the anatomical and functional state of every structure of the body. Kidneys, liver, stomach, muscles and others - all this is inspected by the brain, carefully and painstakingly coordinating and regulating every millimeter of tissue. And in case of failure, it corrects and selects suitable model behavior. Thus, thanks to the pathways, the human body is characterized by autonomy, self-regulation and adaptability to the external environment.

Brain pathways

A pathway is a collection of nerve cells whose function is to exchange information between different areas bodies.

• Associative nerve fibers. These cells connect various nerve centers located in the same hemisphere.
• Commissural fibers. This group is responsible for the exchange of information between similar centers of the brain.
• Projection nerve fibers. This category of fibers articulates the brain with the spinal cord.
• Exteroceptive pathways. They carry electrical impulses from the skin and other sensory organs to the spinal cord.
• Proprioceptive. This group of pathways carries signals from tendons, muscles, ligaments and joints.
• Interoceptive pathways. The fibers of this tract originate from internal organs, vessels and intestinal mesenteries.

Interaction with neurotransmitters

Neurons of different locations communicate with each other using electrical impulses of a chemical nature. So, what is the basis of their education? There are so-called neurotransmitters (neurotransmitters) - complex chemical compounds. On the surface of the axon there is a nerve synapse - the contact surface. On one side there is a presynaptic cleft, and on the other there is a postsynaptic cleft. Between them there is a gap - this is the synapse. On the presynaptic part of the receptor there are sacs (vesicles) containing a certain amount of neurotransmitters (quanta).

When the impulse approaches the first part of the synapse, a complex biochemical cascade mechanism is initiated, as a result of which the sacs with mediators are opened, and quanta of mediator substances smoothly flow into the gap. At this stage, the impulse disappears and reappears only when the neurotransmitters reach the postsynaptic cleft. Then biochemical processes are activated again with the opening of the gates for mediators and those, acting on the smallest receptors, are converted into an electrical impulse that goes further into the depths of the nerve fibers.

Meanwhile, they allocate different groups these same neurotransmitters, namely:

• Inhibitory neurotransmitters are a group of substances that exert an inhibitory effect on excitation. These include:
  • gamma-aminobutyric acid (GABA);
  • glycine.
• Exciting mediators:
  • acetylcholine;
  • dopamine;
  • serotonin;
  • norepinephrine;
  • adrenalin.

Do nerve cells recover?

For a long time it was believed that neurons are not capable of division. However, such a statement, according to modern research, turned out to be false: in some parts of the brain the process of neurogenesis of neurocyte precursors occurs. In addition, brain tissue has remarkable abilities for neuroplasticity. There are many cases where a healthy part of the brain takes over the function of a damaged one.

Many experts in the field of neurophysiology have wondered how to restore brain neurons. Recent research by American scientists has revealed that for timely and proper regeneration of neurocytes, it is not necessary to consume expensive drugs. To do this, you just need to create the right sleep schedule and eat right, including B vitamins and low-calorie foods in your diet.

In the event of a violation neural connections brain, they are able to recover. However, there are serious pathologies nerve connections and pathways such as motor neuron disease. Then you need to contact a specialized clinical care, where neurologists can find out the cause of the pathology and formulate the correct treatment.

People who have previously consumed or are drinking alcohol often ask the question of how to restore brain neurons after alcohol. A specialist would answer that for this you need to systematically work on your health. The range of events includes balanced diet, regular exercise, mental activity, walks and travel. It has been proven that the neural connections of the brain develop through the study and contemplation of information that is completely new to humans.

In conditions of oversaturation with unnecessary information, the existence of a fast food market and a sedentary lifestyle, the brain is qualitatively susceptible to various damages. Atherosclerosis, thrombotic formation on blood vessels, chronic stress, infections - all this is a direct road to brain clogging. Despite this, there are medications that restore brain cells. Main and popular group– nootropics. Drugs in this category stimulate metabolism in neurocytes, increase resistance to oxygen deficiency and provide positive effect to various mental processes(memory, attention, thinking). In addition to nootropics, pharmaceutical market offers drugs containing nicotinic acid, strengthening the walls of blood vessels and others. It should be remembered that the restoration of neural connections of the brain when taking various drugs is a long process.

The effect of alcohol on the brain

Alcohol has Negative influence on all organs and systems, and especially on the brain. Ethanol easily penetrates the protective barriers of the brain. The alcohol metabolite, acetaldehyde, is a serious threat to neurons: alcohol dehydrogenase (an enzyme that processes alcohol in the liver) is involved in the process of processing by the body more quantity fluids, including water from the brain. Thus, alcohol compounds simply dry out the brain, drawing water out of it, as a result of which brain structures atrophy and cell death occurs. In the case of one-time consumption of alcohol, such processes are reversible, which cannot be said about chronic use alcohol, when, in addition to organic changes, stable pathological characteristics of an alcoholic are formed. More detailed information about how “The influence of alcohol on the brain” occurs.

The human brain is the most productive in living nature. It makes up up to 2.5% of body weight and is capable of developing throughout life. If you look at the brain from a scientific point of view, it becomes clear that every person is a real superman. Neurons are faster than the Peregrine Falcon, the inability to tickle yourself and juggling instead of nootropics - T&P have collected 10 facts about the human brain that can change our understanding of ourselves.

Your brain is made up of about 100 billion neurons. If each of them were a star, cranium would fit a third of the Milky Way galaxy. There are five divisions in the brain: medulla, hindbrain, which includes the cerebellum and pons, midbrain, diencephalon and forebrain, represented by the cerebral hemispheres. Each of them performs dozens and even hundreds of different functions.

The speed of information transfer in your brain can reach 432 km/h. For comparison, the speed of Sapsan trains running between Moscow and St. Petersburg is about 250 km/h. If the Sapsan moved as fast as your brain works, it would cover the distance between the two cities in 1 hour 36 minutes.

Average number of thoughts that come to your mind every day - about 70,000. With such activity, the brain is forced to constantly forget unnecessary information in order not to overload itself and protect itself from unpleasant emotional experiences. This allows you to think faster and absorb new information more easily.

However, over the course of your life, your long-term memory can store up to 1 quadrillion (1 million billion) individual bits of information . This is equivalent to 25,000 DVDs.

When the brain is awake, it produces between 10 and 23 watts of energy. This is enough to power a light bulb. That is why this item fully justifies its status as a traditional symbol of insights and new ideas.

New physical connections between neurons are created every time you remember something. This can be done not only in the waking state, but also in the phase REM sleep. Scientists have found that in it a person is able to master new information and perform unfamiliar tasks (for example, memorizing pieces of music). During REM sleep, the large muscles of the body relax, brain activity increases, and eyeballs begin to actively move under the eyelids. Every night you experience 9 to 12 “fast” phases. In total, they make up 20 to 25% of night sleep. This means that out of 80 years of life a person spends from 5 to 6.5 years in this state.

Your brain stops actively growing and becomes an “adult” at age 18. However, he does not stop developing. The skills of socialization and communication with other people, for which the prefrontal cortex is responsible, lend themselves especially well to training. It can grow up to 40 years or longer. The ability to grow throughout life is also preserved in other areas: for example, in the hippocampus, which is responsible for memory. Research conducted in the UK has shown that London taxi drivers who know the city well have, on average, a larger brain region than people in other professions. It was especially massive among drivers who worked in the city greatest number years.

The myth that you only use 10% of your brain is not true. Each part of the brain has a known function. For example, thanks to the work of two tiny areas called the amygdala, located inside the temporal lobes of the brain, you can silently recognize the feelings in other people's faces and their moods. But the desire to laugh at a joke requires using five different areas brain.

You not only have five known feelings: vision, hearing, touch, smell and taste. You also have a meta-sense called proprioception , which combines your brain's knowledge of what your muscles are doing with your sense of the size, shape and position of your body in space. Thanks to proprioception, you know where parts of your body are in relation to each other and can eyes closed touch the tip of your nose with your finger. But tickling yourself is impossible: your brain is able to distinguish your own touches from outside touches, even if the latter are expected.

Daily juggling could change your brain in just seven days : in the parietal lobes you would have more white matter responsible for coordination of movements. This proves that the brain can develop and adapt very quickly.

Neurons – special group body cells that distribute information throughout the body. Using electrical and chemical signals, they help the brain coordinate all vital functions.

To simplify, the tasks of the nervous system are to collect signals coming from environment or from the body, assess the situation, decide how to respond to them (for example, change your heart rate), and think about what is happening and remember it. The main tool for performing these tasks is neurons, woven throughout the body in a complex network.

An average estimate of the number of neurons in the brain is 86 billion, each connected to another 1,000 neurons. This creates an incredible network of interactions. Neuron is the basic unit of the nervous system.

Neurons (nerve cells) make up about 10% of the brain, the rest are glial cells and astrocytes, whose function is to maintain and nourish neurons.

What does a neuron look like?

The structure of a neuron can be divided into three parts:

· Neuron body (soma) – receives information. Contains the cell nucleus.

· Dendrites are short processes that receive information from other neurons.

· An axon is a long process that carries information from the neuron body to other cells. Most often, the axon ends in a synapse (contact) with the dendrites of other neurons.

Dendrites and axons are called nerve fibers.

Axons vary greatly in length, from a few millimeters to a meter or more. The longest are the axons of the spinal ganglia.

Types of neurons

Neurons can be classified according to several parameters, for example, by structure or function.

Types of neurons depending on function:

· Efferent (motor) neurons – carry information from the central nervous system (brain and spinal cord) to cells in other parts of the body.

· Afferent (sensitive) neurons - collect information from the whole body and carry it to the central nervous system.

· Interneurons – transmit information between neurons, often within the central nervous system.

How do neurons transmit information?

A neuron, receiving information from other cells, accumulates it until it exceeds a certain threshold. After this, the neuron sends an electrical impulse along the axon - an action potential.

An action potential is generated by the movement of electrically charged particles across the axon membrane.

At rest electric charge inside the neuron is negative relative to its surroundings intercellular fluid. This difference is called membrane potential. Typically it is 70 millivolts.

When the body of the neuron receives enough charge and it fires, depolarization occurs in the adjacent section of the axon - membrane potential rises quickly and then falls in about 1/1000 of a second. This process triggers depolarization of the adjacent section of the axon, and so on, until the impulse travels along the entire length of the axon. After the depolarization process, hyperpolarization occurs - a short-term state of rest; at this moment, impulse transmission is impossible.

The action potential is most often generated by potassium (K+) and sodium (Na+) ions, which move through ion channels from the intercellular fluid into the cell and back, changing the charge of the neuron and making it first positive, and then reducing it.

The action potential ensures that the cell operates according to the “all or nothing” principle, that is, the impulse is either transmitted or not. Weak signals will accumulate in the body of the neuron until their charge is sufficient for transmission along the processes.

Myelin

Myelin is a white, thick substance that covers most axons. This coating provides electrical insulation to the fiber and increases the speed of impulse transmission through it.

Myelinated fiber versus unmyelinated fiber.

Myelin is produced by Schwann cells in the periphery and oligodendrocytes in the central nervous system. Along the fiber, the myelin sheath is interrupted - these are nodes of Ranvier. The action potential moves from interception to interception, allowing rapid transmission of the impulse.

So common and serious illness, How multiple sclerosis, caused by the destruction of the myelin sheath.

How do synapses work?

Neurons and the tissues to which they transmit impulses do not physically touch; there is always a space between the cells - a synapse.

Depending on the method of transmitting information, synapses can be chemical or electrical.

After the signal, moving along the neuron process, reaches the synapse, release occurs chemical substances– neurotransmitters (neurotransmitters) into the space between two neurons. This space is called the synaptic cleft.

Scheme of the structure of a chemical synapse.

A neurotransmitter from a transmitting (presynaptic) neuron, entering the synaptic cleft, interacts with receptors on the membrane of the receiving (postsynaptic) neuron, triggering a whole chain of processes.

Types of chemical synapses:

glutamatergic – the mediator is glutamic acid, has an exciting effect on the synapse;

· GABAergic – the mediator is gamma-aminobutyric acid (GABA), has an inhibitory effect on the synapse;

· cholinergic – the mediator is acetylcholine, which carries out neuromuscular transmission of information;

Adrenergic – the mediator is adrenaline.

Electrical synapses

Electrical synapses are less common and common in the central nervous system. Cells communicate through special protein channels. The presynaptic and postsynaptic membranes in electrical synapses are located close to each other, so the impulse can pass directly from cell to cell.

The speed of impulse transmission through electrical synapses is much higher than through chemical synapses, therefore they are located mainly in those sections where it is necessary fast reaction, for example, those responsible for protective reflexes.

Another difference between the two types of synapses in the direction of information transmission: if chemical synapses can transmit impulse in only one direction, then electric ones are universal in this sense.

Conclusion

Neurons are perhaps the most unusual cells in the body. Every action that the human body performs is ensured by the work of neurons. Complex neural network shapes personality and consciousness. They are responsible for both the most primitive reflexes and the most complex processes related to thinking.