Nervous system is the basis for any type of interaction between living beings in the surrounding world, as well as a system for maintaining homeostasis in multicellular organisms. The higher the organization of a living organism, the more complex the nervous system is. Basic unit nervous system- This neuron- a cell that has short dendritic processes and a long axonal process.
The human nervous system can be divided into CENTRAL and PERIPHERAL, and also separately distinguished autonomic nervous system, which has its representation in both the central and peripheral nervous systems. The central nervous system consists of the brain and spinal cord, and the peripheral nervous system consists of the nerve roots of the spinal cord, cranial, spinal and peripheral nerves, as well as nerve plexuses.
BRAIN comprises:
two hemispheres,
cerebrum brainstem,
cerebellum.
Cerebral hemispheres divided into frontal lobes, parietal, temporal and occipital lobes. The hemispheres of the brain are connected through the corpus callosum.
- The frontal lobes are responsible for intellectual and emotional sphere, thinking and challenging behavior, conscious movements, motor speech and writing skills.
— The temporal lobes are responsible for hearing, sound perception, vestibular information, partial analysis of visual information (for example, recognition of faces), the sensory part of speech, participation in memory formation, influence on the emotional background, and influence on the autonomic nervous system through communication with the limbic system.
- The parietal lobes are responsible for various kinds sensitivity (tactile, pain temperature, deep and complex spatial types of sensitivity), spatial orientation and spatial skills, reading, counting.
— Occipital lobes— perception and analysis of visual information.
Brain stem represented by the diencephalon (thalamus, epithalamus, hypothalamus and pituitary gland), midbrain, pons and medulla oblongata. Brain stem functions are responsible for unconditioned reflexes, influence on the extrapyramidal system, taste, visual, auditory and vestibular reflexes, suprasegmental level of the autonomic system, control of the endocrine system, regulation of homeostasis, hunger and satiety, thirst, regulation of the sleep-wake cycle, regulation of respiration and the cardiovascular system, thermoregulation.
Cerebellum consists of two hemispheres and a vermis that connects the cerebellar hemispheres. Both the cerebral hemispheres and the cerebellar hemispheres are striated with grooves and convolutions. The cerebellar hemispheres also have nuclei with gray matter. The cerebellar hemispheres are responsible for coordination of movements and vestibular function, and the cerebellar vermis is responsible for maintaining balance, posture, and muscle tone. The cerebellum also influences the autonomic nervous system. The brain has four ventricles, in the system of which cerebrospinal fluid circulates and which are connected to the subarachnoid space of the cranial cavity and spinal canal.
Spinal cord consists of the cervical, thoracic, lumbar and sacral sections, has two thickenings: cervical and lumbar, and the central spinal canal (in which the cerebrospinal fluid circulates and which in the upper sections connects with the fourth ventricle of the brain).
Histologically, brain tissue can be divided into Gray matter, which contains neurons, dendrites (short processes of neurons) and glial cells, and white matter, in which axons lie, long processes of neurons covered with myelin. In the brain, gray matter is located mainly in the cerebral cortex, in the basal ganglia of the hemispheres and nuclei of the brainstem (midbrain, pons and medulla oblongata), and in the spinal cord, gray matter is located in depth (in its central parts), and the outer parts of the spinal cord are represented by white matter.
Peripheral nerves can be divided into motor and sensory, forming reflex arcs that are controlled by parts of the central nervous system.
Autonomic nervous system has a division into suprasegmental And segmental.
— The suprasegmental nervous system is located in the limbic-reticular complex (structures of the brain stem, hypothalamus and limbic system).
— The segmental part of the nervous system is divided into the sympathetic, parasympathetic and metasympathetic nervous systems. The sympathetic and parasympathetic nervous systems are also divided into central and peripheral. The central divisions of the parasympathetic nervous system are located in the midbrain and medulla oblongata, and the central divisions of the sympathetic nervous system are located in the spinal cord. The metasympathetic nervous system is organized by nerve plexuses and ganglia in the walls of the internal organs of the chest (heart) and abdominal cavity (intestines, bladder etc.).
The human nervous system consists of tiny cells called nerve cells. Through circuits made up of these cells, nerve impulses travel to the brain, and response impulses to the muscles. In total, there are more than 10 billion in the human body nerve cells.
Different areas of the brain are responsible for a variety of feelings, sensations and moods
Nerve cells are called neurons. Externally, neurons have a variety of shapes: some have the shape of a star, others - a triangle or a spiral. But even such a small detail of the body as neuron, consists of several parts: body, long process - axon and shorter and thinner processes - dendrites. Thanks to the processes, the attachment of cells to each other and their interaction are ensured. The body of a neuron, like any other cell, consists of a nucleus surrounded by cytoplasm and covered with a membrane.
The central organ of the human nervous system that controls its functioning is brain. The human brain is capable of performing much more processes related to thinking, feelings, and emotions than the brains of other living beings. The surface of the human brain is covered with shallow grooves called convolutions. It consists of white and gray matter. With the help of the first there is a connection between the spinal cord and the brain, and the second makes up the cerebral cortex.
The human brain consists of several sections
Medulla oblongata and pons serve for interaction between the brain and the spinal cord. They control the functioning of the digestive and respiratory systems, the work of the heart.
Cerebellum coordinates all human movements. It is the activity of this part of the brain that ensures the accuracy and speed of movements.
Midbrain is responsible for the reaction to external stimuli, that is, it is responsible for the system of sensory organs.
Diencephalon regulates metabolism and body temperature.
The largest parts of the brain are two cerebral hemispheres brain. The hemispheres of the brain allow a person to analyze sensations received through the senses (for example, the taste of food). The hemispheres of the brain are also responsible for speech, thinking, and emotions.
Brain weight- on average it is 1360-1375 grams for men, 1220-1245 grams for women. After rapid growth during the first year of life (a newborn’s brain is 410 grams - 1/8 of body weight; brain weight at the end of the first year is 900 grams - 1/14 of body weight) the brain grows slowly and between 20-30 years it reaches its growth limit, until the age of 50 changes and then begins to decrease in weight. Among animals, humans have the largest brain weight, not only relative, but also absolute. Only the whale has a somewhat heavier brain than a human (2816). The horse's brain weighs 680 g; lion - 250 g; anthropomorphic monkeys 350-400 g, rarely more.
The greater or lesser weight of the brain in different people cannot in itself serve as an indication of their size. mental abilities. On the other hand, people of outstanding ability often have a brain weight that far exceeds the average. The richness of mental organization depends on the quantity and quality of nerve cells in the cortical layer of the hemispheres and, probably, on the number of association fibers of the cerebrum.
The second most important organ of the nervous system is spinal cord. It is located inside the dorsal and cervical vertebrae. The spinal cord is responsible for all human movements and is connected to the brain, which coordinates these movements. The spinal cord together with the brain make up the central nervous system, and the nerve processes make up the peripheral nervous system.
There are several systems in the human body, including digestive, cardiovascular and muscular. The nervous system deserves special attention - it forces the human body to move, react to irritating factors, see and think.
The human nervous system is a set of structures that performs regulation function of absolutely all parts of the body, responsible for movement and sensitivity.
In contact with
Types of the human nervous system
Before answering the question that people are interested in: “how the nervous system works,” it is necessary to understand what it actually consists of and what components it is usually divided into in medicine.
With the types of NS, not everything is so simple - it is classified according to several parameters:
- localization area;
- type of management;
- method of transmitting information;
- functional accessory.
Localization area
The human nervous system, according to its area of localization, is central and peripheral. The first is represented by the brain and bone marrow, and the second consists of nerves and the autonomic network.
The central nervous system performs regulatory functions with all internal and external organs. She forces them to interact with each other. Peripheral is the one that, due to anatomical features, is located outside the spinal cord and brain.
How does the nervous system work? The PNS responds to irritating factors by sending signals to the spinal cord and then to the brain. Afterwards, the central nervous system organs process them and again send signals to the PNS, which causes, for example, the leg muscles to move.
Method of transmitting information
According to this principle, there are reflex and neurohumoral systems. The first is the spinal cord, which is able to respond to stimuli without the participation of the brain.
Interesting! A person does not control the reflex function, since the spinal cord makes decisions on its own. For example, when you touch a hot surface, your hand immediately withdraws, and at the same time you did not even think about making this movement - your reflexes worked.
The neurohumoral system, which includes the brain, must initially process the information; you can control this process. After this, the signals are sent to the PNS, which carries out the commands of your brain center.
Functional affiliation
Speaking about parts of the nervous system, one cannot fail to mention the autonomic one, which in turn is divided into sympathetic, somatic and parasympathetic.
The autonomic system (ANS) is the department that is responsible for regulation of the functioning of lymph nodes, blood vessels, organs and glands(external and internal secretion).
The somatic system is a collection of nerves that are found in bones, muscles and skin. They are the ones who react to all environmental factors and send data to the brain center, and then carry out its orders. Absolutely every muscle movement is controlled by somatic nerves.
Interesting! The right side of the nerves and muscles is controlled by the left hemisphere, and the left by the right.
The sympathetic system is responsible for the release of adrenaline into the blood, controls heart function, lungs and the supply of nutrients to all parts of the body. In addition, it regulates body saturation.
The parasympathetic is responsible for reducing the frequency of movements and also controls the functioning of the lungs, some glands, and the iris. An equally important task is regulating digestion.
Control type
Another clue to the question “how the nervous system works” can be given by a convenient classification by type of control. It is divided into higher and lower activities.
Higher activity controls behavior in environment. All intellectual and creative activity also refers to the highest.
Lower activity is the regulation of all functions within the human body. This type of activity makes all body systems a single whole.
Structure and functions of the NS
We have already figured out that the entire NS should be divided into peripheral, central, autonomic and all of the above, but much more needs to be said about their structure and functions.
Spinal cord
This organ is located in the spinal canal and in essence is a kind of “rope” of nerves. It is divided into gray and white matter, where the former is completely covered by the latter.
Interesting! In cross-section, it is noticeable that the gray matter is woven from nerves in such a way that it resembles a butterfly. This is why it is often called “butterfly wings”.
Total the spinal cord consists of 31 sections, each of which is responsible for a separate group of nerves that control specific muscles.
The spinal cord, as already mentioned, can work without the participation of the brain - we are talking about reflexes that cannot be regulated. In the same turn, it is under the control of the organ of thinking and performs a conductive function.
Brain
This organ is the least studied; many of its functions still raise many questions in scientific circles. It is divided into five departments:
- cerebral hemispheres (forebrain);
- intermediate;
- oblong;
- rear;
- average.
The first section makes up 4/5 of the entire mass of the organ. It is responsible for vision, smell, movement, thinking, hearing, and sensitivity. The medulla oblongata is an incredibly important center that regulates processes such as heartbeat, breathing, protective reflexes, secretion of gastric juice and others.
The middle department controls a function such as. The intermediate plays a role in the formation emotional state. There are also centers responsible for thermoregulation and metabolism in the body.
Brain structure
Nerve structure
The NS is a collection of billions of specific cells. To understand how the nervous system works, it is necessary to talk about its structure.
A nerve is a structure that consists of a certain number of fibers. These, in turn, consist of axons - they are the conductors of all impulses.
The number of fibers in one nerve can vary significantly. Usually it is about one hundred, but There are more than 1.5 million fibers in the human eye.
The axons themselves are covered with a special sheath, which significantly increases the speed of the signal - this allows a person to react to stimuli almost instantly.
The nerves themselves are also different, and therefore they are classified into the following types:
- motor (transmits information from the central nervous system to the muscular system);
- cranial (this includes optic, olfactory and other types of nerves);
- sensitive (transmit information from the PNS to the CNS);
- dorsal (located in and control parts of the body);
- mixed (capable of transmitting information in two directions).
Structure of the nerve trunk
We have already dealt with topics such as “Types of the human nervous system” and “How the nervous system works,” but there is a lot left aside interesting facts that are worthy of mention:
- The amount in our body is greater than the number of people on the entire planet Earth.
- The brain contains about 90–100 billion neurons. If you connect them all into one line, it will reach about 1 thousand km.
- The speed of the pulses reaches almost 300 km/h.
- After the onset of puberty, the mass of the thinking organ increases every year decreases by approximately one gram.
- Men's brains are approximately 1/12 larger than women's.
- The largest organ of thinking was recorded in a mentally ill person.
- Cells of the central nervous system are practically not recoverable, and severe stress and unrest can seriously reduce their number.
- Until now, science has not determined what percentage we use our main thinking organ. There are well-known myths that there are no more than 1%, and geniuses - no more than 10%.
- The size of the thinking organ is not at all does not affect mental activity. Previously, it was believed that men are smarter than the fair sex, but this statement was refuted at the end of the twentieth century.
- Alcoholic drinks greatly suppress the function of synapses (the place of contact between neurons), which significantly slows down mental and motor processes.
We learned what the human nervous system is - it is a complex collection of billions of cells that interact with each other at a speed equal to the movement of the fastest cars in the world.
The nervous system controls the activity of all systems and organs and ensures the body’s connection with the external environment.
Structure of the nervous system
The structural unit of the nervous system is a neuron - a nerve cell with processes. In general, the structure of the nervous system is a collection of neurons that are constantly in contact with each other through special mechanisms– synapses. They differ in function and structure the following types neurons:
- Sensitive or receptor;
- Effector neurons are motor neurons that send impulses to executive bodies(effectors);
- Closing or insertion (conductor).
Conventionally, the structure of the nervous system can be divided into two large sections - somatic (or animal) and autonomic (or autonomic). The somatic system is primarily responsible for communicating the body with the external environment, providing movement, sensitivity and contraction of skeletal muscles. The vegetative system influences growth processes (respiration, metabolism, excretion, etc.). Both systems have a very close relationship, only the autonomic nervous system is more independent and does not depend on the will of a person. That is why it is also called autonomous. Shares autonomous system into sympathetic and parasympathetic.
The entire nervous system consists of central and peripheral. The central part includes the spinal cord and brain, and the peripheral system consists of nerve fibers extending from the brain and spinal cord. If you look at the brain in cross-section, you can see that it consists of white and gray matter.
Gray matter is a collection of nerve cells (with the initial sections of processes extending from their bodies). Individual groups gray matter is also called nuclei.
White matter consists of nerve fibers covered with a myelin sheath (the processes of nerve cells that form gray matter). In the spinal cord and brain, nerve fibers form pathways.
Peripheral nerves are divided into motor, sensory and mixed, depending on what fibers they consist of (motor or sensory). The cell bodies of neurons, whose processes consist of sensory nerves, are located in ganglia outside the brain. The cell bodies of motor neurons are located in the motor nuclei of the brain and the anterior horns of the spinal cord.
Functions of the nervous system
The nervous system has various effects on organs. The three main functions of the nervous system are:
- Triggering, causing or stopping the function of an organ (gland secretion, muscle contraction, etc.);
- Vasomotor, which allows you to change the width of the lumen of blood vessels, thereby regulating blood flow to the organ;
- Trophic, decreasing or increasing metabolism, and, consequently, the consumption of oxygen and nutrients. This allows you to constantly coordinate the functional state of the organ and its need for oxygen and nutrients. When impulses are sent along the motor fibers to the working skeletal muscle, causing its contraction, then at the same time impulses are received that enhance metabolism and dilate blood vessels, which makes it possible to perform energetic work.
Nervous system diseases
Together with the endocrine glands, the nervous system plays a decisive role in the functioning of the body. It is responsible for the coordinated functioning of all systems and organs of the human body and unites the spinal cord, brain and peripheral system. Motor activity and sensitivity of the body are maintained thanks to nerve endings. And thanks to the autonomic system, the cardiovascular system and other organs are inverted.
Therefore, dysfunction of the nervous system affects the functioning of all systems and organs.
All diseases of the nervous system can be divided into infectious, hereditary, vascular, traumatic and chronically progressive.
Hereditary diseases are genomic and chromosomal. The most famous and common chromosomal disease is Down syndrome. This disease is characterized by the following symptoms: disorders of the musculoskeletal system, endocrine system, lack of mental abilities.
Traumatic lesions of the nervous system occur due to bruises and injuries, or when the brain or spinal cord is compressed. Such diseases are usually accompanied by vomiting, nausea, memory loss, disturbances of consciousness, and loss of sensitivity.
Vascular diseases predominantly develop against the background of atherosclerosis or hypertension. This category includes chronic cerebrovascular insufficiency and cerebrovascular accident. Characterized by the following symptoms: attacks of vomiting and nausea, headache, impaired motor activity, decreased sensitivity.
Chronically progressive diseases, as a rule, develop due to metabolic disorders, exposure to infection, intoxication of the body, or due to abnormalities in the structure of the nervous system. Such diseases include sclerosis, myasthenia gravis, etc. These diseases usually gradually progress, reducing the performance of certain systems and organs.
Causes of diseases of the nervous system:
It is also possible to transmit placental diseases of the nervous system during pregnancy (cytomegalovirus, rubella), as well as through the peripheral system (poliomyelitis, rabies, herpes, meningoencephalitis).
In addition, the nervous system is negatively affected by endocrine, heart, kidney diseases, malnutrition, chemical and medications, heavy metals.
Nervous system consists of winding networks of nerve cells that make up various interconnected structures and control all the activities of the body, both desired and conscious actions, and reflexes and automatic actions; The nervous system allows us to interact with the outside world and is also responsible for mental activity.
The nervous system consists of various interconnected structures that together constitute an anatomical and physiological unit. consists of organs located inside the skull (brain, cerebellum, brain stem) and spine (spinal cord); is responsible for interpreting the condition and various needs of the body based on the information received, in order to then generate commands designed to produce appropriate responses.
consists of many nerves that go to the brain (cerebral pairs) and the spinal cord (vertebral nerves); acts as a transmitter of sensory stimuli to the brain and commands from the brain to the organs responsible for their execution. The autonomic nervous system controls the functions of numerous organs and tissues through antagonistic effects: the sympathetic system is activated during anxiety, and the parasympathetic system is activated during rest.
central nervous system
Includes the spinal cord and brain structures.