Typically, the human nervous system consists of a central nervous system(CNS - brain and spinal cord), as well as peripheral system(nerves coming from the spinal cord and brain). The importance of the nervous system in the life of the body is extremely great. The main function of the nervous system is to regulate the behavior and life of the human body in the surrounding world. Absolutely every human organ begins, changes, and stops its activity precisely under the influence of the nervous system. Under the influence of the nervous system, the blood vessels in working organs dilate, as a result of which much more blood enters them.
At the same time, in other organs there is a certain decrease in the lumen of blood vessels, which causes less blood flow to them. Thus, with the participation of the nervous system in the human body, depending on needs, a kind of redistribution of blood occurs. There are absolutely no processes in the human body that would occur without the participation of the central nervous system. In the human body, the connections between organs through the nervous system are very complex and numerous. The activity of the nervous system is manifested in reflexes.
The importance of the nervous system
The nervous system establishes communication between the body and outside world. Receptors perceive the action of stimuli from the surrounding world. From them, signals enter the nervous system. So, if the ambient temperature is very high (for example, in a hot workshop), then the skin receptors are irritated, from which signals enter the nervous system along the centripetal nerves. From the nervous system, signals travel through the centrifugal nerves to the sweat glands. Therefore, the activity of the sweat glands increases, the skin becomes covered with sweat. The evaporation of sweat from the surface of the skin is accompanied by heat loss, as a result of which the body protects itself from overheating.
A person’s relationship with the external world around him, with society, is not limited to innate unconditioned reflexes. They are not limited to conditional ones either, i.e. acquired reflexes. This relationship is very complex. A vital role belongs to the psyche, i.e. sensations, feelings, thoughts, consciousness that determine human behavior. The psyche is a property of the human brain, a reflection in it of the surrounding world of nature and society.
The psyche depends on physiological processes in the human brain and cannot exist outside the brain, without it, in the absence of its activity. For example, during complete sleep a person does not feel or think, since at this time the nerve cells cerebral hemispheres the brain is inhibited.
Properties of nerve tissue
Main properties nerve tissue are excitability and conductivity. The speed of excitation along human nerves is from 0.5 to 160 meters per second. Excitability and conductivity are properties of each neuron. The central nervous system consists of many billions of neurons. In it, neurons are interconnected by the contact of their processes, and therefore the excitation that arises in one nerve cell is transmitted through its processes to neighboring nerve cells.
In the cells of the central nervous system, excitation arises from various reasons: excitation can come from centripetal nerves, bringing signals from receptors connected by these nerves to a given group of nerve cells. Excitation of nerve cells can also be caused chemicals carried by blood to the brain. For example, accumulation in the blood carbon dioxide stimulates the respiratory center. Excitation of the nervous system is also caused by an increase in body temperature, for example, delirium at high temperature.
A lot of waste occurs in nerve cells during their activity. organic matter and oxygen. Nerve cells consume more oxygen than cells of other tissues and organs. The brain uses approximately 25% of the oxygen supplied to the body. Since oxygen is delivered to the brain by blood, the slightest violation in the blood circulation of the brain (blockage of blood vessels, their rupture) can cause the death of nerve cells.
: ensuring coordinated work of tissue cells, organs and body systems into a single whole; regulation of the activities of all organs and systems; communication between the body and the external environment, adaptation to rapidly changing living conditions; material basis conscious activity human: speech, thinking, behavior.
2. Nervous tissue consists of neurons and auxiliary cells (glial cells, neuroglia; Schwann cells).
3. Neuron- nerve cell with processes (one that transmits excitation only from the cell - the axon, and several that transmit excitation to the cell - dendrites).
4. Neurons, connecting to each other using an axon (the longest process of all), form a neural network.
5. Main sections - brain and spinal cord; There is also a peripheral nervous system.
6. Gray matterspinal cord formed by a cluster of neuron cell bodies and has the shape of a butterfly; white matter The spinal cord is formed by pathways. Gray matter the brain is formed in exactly the same way and covers the cerebral hemispheres; white matter formed by nerve fibers that connect the cortex of one gyrus with the cortex of other gyri.
7. Somatic nervous system innervates striated skeletal muscles and sensory organs, providing voluntary motor and sensory functions, connecting the body with the environment and rapid reactions to its changes.
8.Autonomic (autonomic) nervous system innervates the smooth muscles of internal organs, blood vessels, skin, heart muscle and glands; controls the activity of internal organs involved in the functions of nutrition, respiration, excretion, and adapts their work to the needs of the body and conditions external environment.
9. Under the influence of norepinephrine (this is a neurotransmitter sympathetic nervous system) the rhythm and strength of heart contractions increases; vasoconstriction; dilation of the bronchi and pupil; decreased secretion of the glands of the stomach and intestines, relaxation of intestinal smooth muscles; increased salivation. Influenced acetylcholine(this is a mediator parasympathetic nervous system) the rhythm and strength of heart contraction decreases; the lumen of the bronchi and pupil narrows; pulmonary ventilation and gastrointestinal peristalsis are enhanced; The secretion of the glands of the stomach, intestines and pancreas increases.
10. Sympathetic and parasympathetic nerves tend to have opposite effects on organ function. For example, sympathetic nerves speed up the rhythm and increase the strength of heart contractions, while parasympathetic (vagus nerve) slow down the rhythm and reduce their strength; etc.
You already know that the existence of an organism in a complex, constantly changing world is impossible without the regulation and coordination of its activities. The leading role in this process belongs to the nervous system. In addition, the human nervous system is material basis his mental activity(thinking, speaking, complex shapes social behavior).
The basis of the nervous system is made up of nerve cells - neurons. They perform the functions of perception, processing, transmission and storage of information. Nerve cells consist of a body, processes and nerve endings. Cell bodies can be different in shape, and processes can be different lengths: short ones are called dendrites, long ones are called axons. Clusters of neuron cell bodies in the brain and spinal cord form Gray matter. Neuronal processes (nerve fibers) make up the white matter of the brain and spinal cord, and are also part of the nerves.
Long processes of nerve cells (axons) penetrate the body and provide communication between the brain and spinal cord and any part of the body. The branches of neuron processes have nerve endings - receptors. These are special structures that convert perceived stimuli into nerve impulses. Nerve impulses travel along nerve fibers at speeds from 0.5 to 120 m/s. Depending on the functions performed, sensory, intercalary and motor neurons are distinguished.
Nerve cells at the points of connection with each other form special contacts - synapses. Neurons, in contact with each other, form chains. Nerve impulses travel along such chains of neurons.
The nervous system is divided into central and peripheral based on its location in the body. The neutral nervous system includes the spinal cord and brain, the peripheral nervous system includes nerves, nerve ganglia and nerve endings. Nerves are bundles of long processes of nerve cells that extend beyond the brain and spinal cord. The bundles are covered with connective tissue that forms the nerve sheaths. Nerve ganglia are clusters of neuron cell bodies outside the central nervous system.
According to another classification, the nervous system is conventionally divided into somatic and autonomic (autonomic). The somatic nervous system controls the functioning of skeletal muscles. Thanks to it, the body maintains contact with the external environment through the senses. All human movements are performed by contracting skeletal muscles. The functions of the somatic nervous system are controlled by our consciousness. Supreme center The somatic nervous system is the cerebral cortex.
The autonomic (autonomic) nervous system controls the functioning of internal organs, providing them best job when the external environment changes or the type of activity of the organism changes. This system is not usually controlled by our consciousness, unlike the somatic nervous system. However, at the level of the hemispheres and brain stem nerve centers It is difficult to separate the somatic and autonomic nervous systems.
The autonomic nervous system is divided into two divisions: sympathetic and parasympathetic.
Most organs of the human body are controlled by both the sympathetic and parasympathetic divisions of the autonomic nervous system. Sympathetic regulation more often prevails in cases when a person is in active state, doing some difficult physical or mental work. Sympathetic influences improve blood supply to muscles and enhance heart function. Parasympathetic nervous influences on organs intensify in cases where a person is at rest: the work of the heart slows down, blood pressure in the arterial vessels decreases, but the work gastrointestinal tract intensifies. This is understandable: when should we digest food if not during rest, in a calm state.
The activity of the nervous system has reached great perfection and complexity. It is based on reflexes (from the Latin “reflexus” - reflection) - the body’s responses to the influence of the external environment or to changes in it internal state performed with the participation of the nervous system.
Many of our actions occur automatically. For example, when the light is too bright, we close our eyes, turn our heads at a sharp sound, pull our hand away from a hot object - this is without conditioned reflexes. They are carried out without any preconditions. Unconditioned reflexes are inherited, which is why they are also called congenital. And conditioned reflexes are reflexes acquired as a result life experience. For example, if you have been waking up at the same hour for a long time, then after a while you will wake up at right moment and without a call.
The path along which a nerve impulse travels from its point of origin to the working organ is called a reflex arc. The reflex arc can be simple or complex. Typically, it consists of sensory neurons with their sensitive endings - receptors, interneurons and executive (effector) neurons (motor or secretory). The shortest reflex arc can consist of two neurons: sensitive and executive. Complex arcs consist of many neurons.
All our actions occur with the participation and control of the central nervous system - the brain and spinal cord. For example, a child, seeing a familiar toy, reaches out to it: a command came from the brain along the executive nerve pathways - what to do. These are direct connections. The child grabbed the toy. - immediately signals about the results of activity were sent along the sensitive neurons. This feedbacks. Thanks to them, the brain can control the accuracy of command execution and make the necessary adjustments to the work of the executive organs.
The nervous and humoral ways of regulating the functions of our body are closely interconnected: the nervous system controls the work of the endocrine glands, and they, in turn, influence the nerve centers with the help of secreted hormones. Thus, the system of endocrine glands, together with the nervous system, carries out neurohumoral regulation of organ activity.
- Brain function is very demanding high costs energy. The main source of energy for the brain is glucose, which people absorb from food. But glucose still needs to be transported through the bloodstream from the gastrointestinal tract to the brain. This is why so much blood flows through the vessels of the brain: 1.0-1.3 liters per minute.
- Brain neurons are very sensitive to interruption of oxygen and glucose supply. If you deprive the brain of blood flow, and therefore the delivery of substances to it, for just 1 minute, then loss of consciousness occurs. But with training you can achieve a lot. For example, girls involved in synchronized swimming can remain underwater for several minutes.
Test your knowledge
- What role does the nervous system play in the body?
- How is a nerve cell structured?
- What is a synapse?
- How is excitation transmitted through the nervous system?
- What is a reflex? What reflexes do you know?
- What neurons does the reflex arc consist of?
- What organs make up the central nervous system?
- What does the somatic nervous system innervate?
- How does the function of the autonomic nervous system differ from the function of the somatic nervous system?
Think
Why does the nervous system play a role in coordinating and regulating the body’s activities? leading place? Compare the speed of conduction nerve impulse with the speed of blood flow in the aorta (0.5 m/s). Draw a conclusion about the difference between nervous and humoral regulation.
The nervous system consists of the central and peripheral parts. The central nervous system is formed by the brain and spinal cord, the peripheral - by nerves, nerve ganglia and nerve endings. The structure of the nervous system is based on a nerve cell (neuron), and its activity is based on a reflex. The path along which excitation passes from the point of origin of the nerve impulse to the working organ is called a reflex arc.
Of all the body systems, the nervous system is the most important. The coordinated work of all other organs, tissues and cells depends on it. The main importance for the body is that due to it it functions as a single whole. In addition, it controls the body’s contacts with the external environment.
Thanks to this system, a person can think and analyze events. The deep significance of the nervous system for the body is much more important: it controls everything, including the processes of breathing, hematopoiesis, feelings of hunger and thirst, and it is also responsible for all our reflexes, including the most primitive ones. To understand its importance for our body, you should know (at least at a primitive level) its structure.
What does the nervous system contain?
It is formed by nervous tissue, which includes neurons and satellite cells (astrocytes). Let's briefly describe their purpose:
- Neuron - main functional unit nervous tissue. It is these cells that are responsible for both thinking and all other functions of the entire system.
- Satellite cells perform trophic and support functions. It is currently believed that they still play an important role in the mechanism long-term memory, although this hypothesis needs clarification.
Let's continue to discuss the structure and significance of the nervous system.
Neuron structure
This cell, which is responsible for almost everything that happens in the body, consists of a body and processes. They are divided into two types: axons and dendrites. The first of them extend from the cell in a single copy, long. On the contrary, the dendrites are not very prominent in size and are highly branched. As a rule, each of them can have several. They go along the dendrites into the cell.
The axon is long and practically does not branch. It carries impulses out of the nerve cell body. The length of this process can exceed several tens of centimeters. Signals are transmitted through it using electrical discharges, almost instantly.
A small digression. It should be noted that the meaning, structure and functioning of the nervous system are so complex and diverse that many functional features, about some particularly difficult biochemical processes that occur deep in the central nervous system, scientists are just beginning to guess.
The axons are covered with a sheath of fat-like substance that serves as an insulator. It is the accumulations of these processes that form the white matter of the nervous system. The body of the neuron itself and the dendrites do not have any shell. Clusters of these objects are called gray matter.
We continue to study the structure and significance of the nervous system. You must clearly understand that neurons are largely differentiated; there are no universal cells of this type. Let's continue to talk about the importance of the nervous system. Overall plan It is impossible to imagine the nervous system even approximately, if you do not know about the structure of the neuron, its functional unit.
What are neurons?
It should not be assumed that all neurons are the same. On the contrary, they differ greatly from each other in their form and function. Sensory transmit impulses from the sense organs to the brain. Their bodies are located in large nerve ganglia of the body. By the way, this is the name given to large clusters of neurons outside the brain and spinal cord. The motor variety, on the contrary, transmits impulses from the brain to the muscles and internal organs.
Interneurons are responsible for interaction and transmission of information between sensory and motor cells. Their processes are very short, play the role of “layers”, and do not extend beyond the brain. Thus, the brain receives information from all systems and organs of the body.
So, let's summarize. What is the main significance of the nervous system for the body? Let's list:
- It receives signals from the senses, smell and touch receptors.
- The neurons analyze the received information.
- The corresponding impulse is transmitted to the executive organ (muscle, for example).
- The body adequately responds to an irritating environmental factor.
Impulses from and to the brain are transmitted not only through individual processes of neurons, but also through specialized nerves.
What are nerves?
IN Everyday life We constantly hear this word, but somehow we don’t think about its true meaning. But the nervous system and its role in the body are so great that you should know about it!
Nerves are precisely clusters of long processes of neurons that are covered with a special containment. If there are processes under this “winding”, then the nerves themselves are called motor nerves. Typically, nerve trunks contain both dendrites and axons. In this case they are called mixed. They differ in that they can transmit nerve impulses in both directions.
Divisions of the nervous system
It has two main sections: internal and peripheral. The central section includes the brain and spinal cord, protected by the bones of the skull and spinal column. Accordingly, the periphery includes nerve ganglia and individual
The part of the nervous system that controls the functioning of skeletal muscles is called somatic. Thus, the importance of the nervous system for the body in this case is extremely important: it is “somatics” that allows us to move our arms and legs. An autonomous department of the system is responsible for the work of internal organs. Its functioning is not subject to the conscious will of man. Simply put, you hardly know how to control the digestion process, slow it down or speed it up.
Thus, the importance of the nervous system in regulating the functions of the body is extremely great: it controls even those processes that most people are not even aware of. Of course, if everything is in order with their body and everything functions in a “normal” mode.
In this department there are two large “structural units”: sympathetic and almost everything internal organs are innervated by the nerve trunks precisely from it. The effect on the body in these departments is diametrically opposite.
For example, sympathy enhances the contractions of the cardiac striated muscles, and parasympathetic slows down this process; it is responsible for digestion. Thus, the role of the parasympathetic nervous system in the body is even more important. She is responsible for breathing and other vital important processes.
Reflex
What is the significance of the nervous system in absolutely unconditional reaction humans and animals to some kind of irritation from the external environment? Simply put, how is reflex activity carried out?
As you know, a mechanism that we know as a “reflex arc” is responsible for this. This is the path along which nerve impulses pass at the moment when the body responds with a reflex to irritation. It consists of the following sections: a receptor, a sensitive pathway, some part of the nervous system responsible for the reflex, a path along which the signal travels, as well as a working organ.
This is how great the importance of the nervous system is in human life. When something is disturbed in it, for a sick person it can be a real feat to independently. It’s amazing how few people think about the importance of nervous tissue!
About segments of the reflex arc
Each arc begins with a sensitive receptor. Each of them perceives only some certain type irritant. Receptors are responsible for converting environmental influences into nerve impulses. Impulses that move skeletal muscles, trigger some important processes and perform the same important function, have purely electrical nature. With help sensory neuron impulses are transmitted to the central nervous system.
Note that almost all reflex arcs contain interneurons.
Many people believe that a reflex reaction is completely unconscious process, which, once fixed, remains completely unchanged. But this is far from true. The fact is that the nervous system not only receives the signal received from the receptor, but analyzes it, assessing the effectiveness of the reaction. Simply put, this is how people, when training, bring their actions not only to reflexive automatism, but also do it perfectly.
Now let's talk about the importance of the nervous system in the context of discussing the spinal cord. Some believe that it serves solely to transmit impulses from the brain to the lower parts. A grave mistake, since the role of this organ is much more important.
Structure of the spinal cord
The spinal cord is located in the spinal canal. Bounded and protected by physical cavities - the bones of the skull, as well as the spinal column itself. The theoretical (anatomical) boundary between the spinal cord and the brain runs between the occipital bone and the atlas.
In humans, it looks like a white cord, the diameter of which is approximately 1 centimeter. The canal itself is filled with cerebrospinal fluid. On the surface of the organ itself there are two deep longitudinal grooves that divide it into right and left parts. If you cut the brain in half, you can see a rather beautiful pattern that resembles a butterfly.
Its body is formed by neurons (intercalary and motor). As we have already said, which closes them on all sides, consists of long processes of neurons. They, passing up and down along the spinal cord, form the ascending and descending canals.
What functions does the spinal cord perform?
It is entrusted with two main tasks: reflexes and the role of the conduction path. Due to the reflex function, we are able to perform many movements. All contractions of the skeletal muscles of the body (except for the muscles of the head) are in one way or another connected with reflex arcs, which directly depend on the activity of the spinal cord.
In other words, the role of the nervous system in the life of the body is extremely multifaceted: in the regulation of the work of organs and systems, those parts of it that many people rarely remember are sometimes involved.
We are not exaggerating at all! After all, the spinal cord, in company with its “head colleague,” regulates the correct functioning of an incredible number of organs: digestive system and the heart, excretory system and reproductive organs. Due to white matter synchronization is carried out, their completely simultaneous reaction to external and internal stimuli is ensured.
Important! Do not forget that the spinal cord is still subordinate to the brain in everything. There are often cases when, as a result of injury, accident or illness, the connection between the brain and spinal cord is completely interrupted in a person. The first one works absolutely fine in such cases. But almost all reflexes, the zones of which are located below, completely disappear.
Such people can best case scenario move your arms, turn your head slightly, but Bottom part their bodies are completely motionless and devoid of any sensitivity.
Brain
Located in the cranium. It is divided into the following sections: medulla oblongata, cerebellum, pons, intermediate and middle sections, as well as hemispheres. As in the previous case, there is white and gray matter. White connects with each other both parts of the brain itself and with the spinal region. Thanks to this, the entire central nervous system functions as a single whole.
Unlike the spinal cord, here the gray matter extends to the surface of the organ, forming its cortex, cortex.
The medulla oblongata is actually a continuation of the spinal region and is necessary for connecting these parts of the nervous system with each other. It is responsible for breathing, digestion and other unconscious functions, and therefore its damage is fatal.
Meaning of individual components
The cerebellum regulates motor functions. The midbrain serves as a transit point for many reflex arcs. Medulla oblongata, pons and midbrain form a kind of trunk that connects various departments and performs many reflex functions. The cortex is the youngest and most important section. It is through it that we think, think, and store our memories. Cortex trauma can lead to complete loss of personality.
There are often cases when people who have been in a state for a long time clinical death, drowned, after especially terrible accidents, were found alive as a result of intensive cardiac and pulmonary resuscitation. But it’s extremely difficult to call such a state life. The neurons of the cortex die very quickly, after which the person turns into a “vegetable”. He can't speak, he has no memory of past life(with rare exceptions), he cannot take care of himself at all.
This is the importance of the nervous system in the life of the body.
The nervous system plays vital role in the regulation of body functions. It ensures the coordinated functioning of cells, tissues, organs and their systems. In this case, the body functions as a single whole. Thanks to the nervous system, the body communicates with the external environment.
The entire nervous system is divided into central and peripheral. The central nervous system includes the brain and spinal cord. From them, nerve fibers radiate throughout the body - the peripheral nervous system. It connects the brain with the senses and with the executive organs - muscles and glands.
All living organisms have the ability to respond to physical and chemical changes in the environment.
Stimuli from the external environment (light, sound, smell, touch, etc.) are converted by special sensitive cells (receptors) into nerve impulses - a series of electrical and chemical changes in the nerve fiber. Nerve impulses are transmitted along sensory (afferent) nerve fibers to the spinal cord and brain. Here, appropriate command impulses are generated, which are transmitted along motor (efferent) nerve fibers to the executive organs (muscles, glands). These executive bodies are called effectors.
The main function of the nervous system is integration external influence with the corresponding adaptive reaction of the body.
The structural unit of the nervous system is a nerve cell - a neuron.
The central nervous system consists of the brain and spinal cord. The brain is divided into the brainstem and forebrain. The brainstem consists of the medulla oblongata and midbrain. Forebrain divided into intermediate and final.
All parts of the brain have their own functions.
So, diencephalon consists of the hypothalamus - the center of emotions and vital needs (hunger, thirst, libido), the limbic system (in charge of emotional-impulsive behavior) and the thalamus (filtering and primary processing of sensory information).
In humans, the cerebral cortex is especially developed - an organ of higher mental functions. It has a thickness of 3 mm, and total area its average is 0.25 m 2.
The bark consists of six layers. The cells of the cerebral cortex are interconnected.
There are about 15 billion of them.
Different cortical neurons have their own specific function. One group of neurons performs the function of analysis (crushing, dismembering the nerve impulse), another group carries out synthesis, combines impulses coming from various organs senses and parts of the brain (associative neurons). There is a system of neurons that retains traces of previous influences and compares new influences with existing traces.
Based on the characteristics of the microscopic structure, the entire cerebral cortex is divided into several dozen structural units- fields, and according to the location of its parts - into four lobes: occipital, temporal, parietal and frontal.
The human cerebral cortex is a holistically functioning organ, although its individual parts (regions) are functionally specialized (for example, the occipital cortex performs complex visual functions, the frontotemporal cortex performs speech, the temporal cortex performs auditory functions). Largest part The motor zone of the human cerebral cortex is associated with the regulation of the movement of the labor organ (hand) and speech organs.
All parts of the cerebral cortex are interconnected; they are also connected to lower departments brain, which carry out the most important vital functions. Subcortical formations, regulating innate unconditioned reflex activity, are the area of those processes that are subjectively felt in the form of emotions.
The human brain contains all those structures that arose at various stages of the evolution of living organisms. They contain the “experience” accumulated in the process of everything evolutionary development. This indicates common origin humans and animals.
As the organization of animals at various stages of evolution becomes more complex, the importance of the cerebral cortex increases more and more. The nervous system plays a critical role in regulating body functions. It ensures the coordinated functioning of cells, tissues, organs and their systems. In this case, the body functions as a single whole. Thanks to the nervous system, the body communicates with the external environment.
The activity of the nervous system underlies feelings, learning, memory, speech and thinking - mental processes, with the help of which a person not only learns environment, but can also actively change it.