Nervous system. Structure and functions of the human nervous system The nervous system consists of

Nervous system is a set of special structures that unites and coordinates the activities of all organs and systems of the body in constant interaction with the external environment.

The meaning of the nervous system:

Maintaining a constant composition of the internal environment of the body.

Coordination of the work of bodies.

Recognizing the external environment to meet needs. Orientation in the external environment.

Ensuring conscious regulation of behavior. Psyche - speech, thinking, social behavior.

Structure of the human nervous system diagram

The human nervous system is divided into the central nervous system (includes the brain and spinal cord) and the peripheral nervous system (includes nerve endings, nerves, nerve ganglia).

	accumulations of long processes of nerve cells outside the central nervous system, enclosed in a common connective tissue membrane and conducting nerve impulses.
Sensory nerves	formed by dendrites of sensory neurons.
Motor nerves	formed by the axons of motor neurons.
Mixed nerves	formed by both axons and dendrites.
Nerve nodes	accumulations of neuron cell bodies outside the central nervous system.
Receptor nerve endings	terminal formations of dendrites in organs; perceive irritations and convert them into nerve impulses.
Effector nerve endings	terminal formations of axons in working organs: muscles, glands.
Nerve impulse	an electrical signal propagating across cell membranes.
Gray matter	these are the bodies of neurons.
White matter	these are processes of neurons
Excitation	putting the cell into operation.
Braking	inhibition of cell function.

Functional division of the nervous system

Functionally, the nervous system is divided into Somatic (subordinate to the will of a person) and Autonomous (vegetative, which is not subject to the will of a person). The somatic nervous system regulates the functioning of skeletal muscles; its motor centers are located in the cerebral cortex. The autonomic or autonomic nervous system regulates the functioning of internal organs, glands, blood vessels and the heart. Its autonomic centers are located in the hypothalamus.

The autonomic system is in turn divided into the sympathetic and parasympathetic systems. The sympathetic system is activated during intense work that requires energy expenditure. The parasympathetic system helps restore energy reserves during sleep and rest.

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A source of information:

Biology in tables and diagrams./ Edition 2, - St. Petersburg: 2004.

Rezanova E.A. Human biology. In tables and diagrams./ M.: 2008.

The nervous system consists of the spinal cord, brain, sensory organs, and all the nerve cells that connect these organs to the rest of the body. Together, these organs are responsible for controlling the body and communicating between its parts. The brain and spinal cord form a control center known as the central nervous system (CNS), where information is evaluated and decisions are made. The sensory nerves and sensory organs of the peripheral nervous system (PNS) monitor... [Read below]

• Head and neck
• Chest and upper back
• Pelvis and lower back
• Arms and hands
• Legs and feet

[Start at the top] ... conditions inside and outside the body and send this information to the central nervous system. Efferent nerves in the PNS carry signals from the control center to muscles, glands, and organs to regulate their functions.

Nervous tissue

Most tissues of the nervous system are composed of two classes of cells: neurons and neuroglia.

Neurons, also known as nerve cells, communicate in the body through the transmission of electrochemical signals. Neurons are quite different from other cells in the body due to the many complex cellular processes that occur in their central body. The cell body is the roughly circular part of the neuron that contains the nucleus, mitochondria, and most of the cell's organelles. Small tree-like structures called dendrites extend from the cell body to receive stimuli from the environment, these are called receptors. Transmitting nerve cells are called axons, they extend from the cell body to send signals forward to other neurons or effector cells in the body.

There are 3 main classes of neurons: afferent neurons, efferent neurons and interneurons.
Afferent neurons. Also known as sensory neurons, they transmit afferent sensory signals to the central nervous system from receptors in the body.

Efferent neurons. Also known as motor neurons, efferent neurons carry signals from the central nervous system to effectors in the body such as muscles and glands.

Interneurons. Interneurons form complex networks in the central nervous system to integrate information received from afferent neurons and direct body function through efferent neurons.
Neuroglia. Neuroglia, also known as glial cells, act as the “messenger” of cells in the nervous system. Each neuron in the body is surrounded by anywhere from 6 to 60 neuroglia, which protect, nourish and insulate the neuron. Because neurons are extremely specialized cells that are essential to the body's functioning and almost never reproduce, neuroglia are vital to maintaining a functional nervous system.

Brain

The brain, a soft, wrinkled organ that weighs about 1.2 kg, is located inside the cranial cavity, where the bones of the skull surround and protect it. The brain's approximately 100 billion neurons form the body's main control center. The brain and spinal cord together form the central nervous system (CNS), where information is processed and responses are generated. The brain is the seat of higher mental functions such as consciousness, memory, planning and voluntary action, and it also controls lower body functions such as maintaining breathing, heart rate, blood pressure and digestion.
Spinal cord
It is a long, thin mass of grouped neurons that carry information, located in the spinal cavity. Beginning in the medulla oblongata at its upper end and continuing downward in the lumbar region of the spine. In the lumbar region, the spinal cord divides into a bundle of individual nerves called the cauda equina (due to its resemblance to a horse's tail), which continues down to the sacrum and coccyx. The white matter of the spinal cord acts as the main conduit for nerve signals from the brain to the body. The gray matter of the spinal cord integrates reflexes to stimuli.

Nerves

Nerves are bundles of axons in the peripheral nervous system (PNS) that act as information conduits for transmitting signals between the brain and spinal cord, as well as the rest of the body. Each axon wrapped in a sheath of connective tissue is called an endoneuritis. Individual axons, grouped into groups of axons, the so-called fascicles, are wrapped in a sheath of connective tissue and are called perineurium. Finally, many fascicles are packed together into another layer of connective tissue called the epineurium to form the entire nerve. The covering of connective tissue that wraps nerves helps protect axons and increase the speed at which they are transmitted within the body.

Afferent, efferent and mixed nerves.
Some of the nerves in the body are specialized to carry information in only one direction, similar to a one-way street. Nerves that carry information from sensory receptors only to the central nervous system are called afferent neurons. Other neurons, known as efferent neurons, carry signals only from the central nervous system to effectors such as muscles and glands. Finally, some nerves are of a mixed type, containing both afferent and efferent axons. Mixed nerve functions are like 2 one-way streets, where afferent axons act as a lane to the central nervous system, and efferent axons act as a lane away from the central nervous system.

Cranial nerves.
There are 12 pairs of cranial nerves extending from the underside of the brain. Each pair of cranial nerves is identified by a Roman numeral from 1 to 12, based on its location along the anterior-posterior axis of the brain. Each nerve also has a descriptive name (eg, olfactory, optic, etc.) that identifies its function or location. Cranial nerves provide direct connections to the brain for special sensory organs, muscles of the head, neck and shoulders, heart and gastrointestinal tract.

Spinal nerves.
There are 31 pairs of spinal nerves located on the left and right sides of the spinal cord. Spinal nerves are mixed nerves that carry both sensory and motor signals between the spinal cord and specific areas of the body. The 31 pairs of nerves in the spinal cord are divided into 5 groups, named after the 5 regions of the spinal column. Thus, there are 8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves and 1 pair of coccygeal nerves. A separate spinal nerve exits the spinal cord through the intervertebral foramina between a pair of vertebrae or between the C1 vertebra and the occipital bone of the skull.

Meninges

The meninges are the protective covering of the central nervous system (CNS). It consists of three layers: the dura mater, the arachnoid mater and the pia mater.

Hard shell.
This is the thickest, toughest and most superficial layer of the shell. Made from dense, irregular connective tissue, it contains many tough collagen fibers and blood vessels. The dura mater protects the central nervous system from external damage, contains cerebrospinal fluid, which surrounds the central nervous system and supplies blood to the nervous tissue of the central nervous system.

Cobweb matter.
Much thinner than the dura mater. It lines the dura mater inside and contains many thin fibers that connect it to the main pia mater. These fibers traverse a fluid-filled space called the subarachnoid space between the arachnoid membrane and the pia mater.

The proper functioning of the nervous system is affected by both physical and psychological stress, so it is important to periodically relieve tension arising from stressful situations. One way to unload is to change from a bad to a good mood, for example, when viewing entertainment sites.

Pia materia.
The pia mater is a thin and very thin layer of tissue that lies on the outside of the brain and spinal cord. Contains many blood vessels that nourish the nervous tissue of the central nervous system. The pia mater penetrates the valleys of the sulci and fissures of the brain, as it covers the entire surface of the central nervous system.
Cerebrospinal fluid
The space surrounding the organs of the central nervous system is filled with a clear fluid known as cerebrospinal fluid (CSF). It is formed from blood plasma with the help of special structures called the choroid plexus. The choroid plexus contains many capillaries lined with epithelial tissue that filters blood plasma and allows filtered fluid to enter the space around the brain.

The newly created CSF flows through the inside of the brain in hollow spaces called ventricles and through a small cavity in the middle of the spinal cord called the central canal. It also flows through the subarachnoid space around the outside of the brain and spinal cord. CSF is continually produced in the choroid plexus and is reabsorbed into the blood in structures called arachnoid villi.

Cerebrospinal fluid provides several vital functions of the central nervous system:
It absorbs shock between the brain and skull, and between the spinal cord and vertebrae. This shock absorption protects the central nervous system from shocks or sudden changes in speed, such as during a car accident.

CSF reduces the mass of the brain and spinal cord due to buoyancy. The brain is a very large but soft organ that requires a large volume of blood to function effectively. The reduced weight in the cerebrospinal fluid allows the brain's blood vessels to remain open and helps protect nerve tissue from the fate of being crushed under its own weight.

It also helps maintain chemical homeostasis in the central nervous system. Since it contains ions, nutrients, oxygen and albumin, which maintain the chemical and osmotic balance of the nervous tissue. CSF also removes waste products that are formed as by-products of cellular metabolism within nerve tissue.

Sense organs

All sense organs are components of the nervous system. Special sensory organs, taste, smell, hearing and balance are known, and specialized organs such as eyes, taste buds and olfactory epithelium have been discovered. Sensory receptors for common senses like touch, temperature and pain are found throughout most of the body. All sensory receptors in the body are connected to afferent neurons, which carry their sensory information to the central nervous system to be processed and integrated.

Functions of the nervous system

It has three main functions: sensory, connective (conductive) and motor.

Sensory.
The sensory function of the nervous system involves collecting information from sensory receptors that control the internal and external conditions of the body. These signals are then transmitted to the central nervous system (CNS) for further processing by afferent neurons (and nerves).

Integration.
Integration is the processing of multiple sensory signals that are transmitted to the central nervous system at any given time. These signals are processed, compared, used to make decisions, discarded, or stored in memory as deemed appropriate. Integration occurs in the gray matter of the brain and spinal cord and is carried out by interneurons. Many interneurons work together to form complex networks that provide this processing power.

Motor function. After networks of interneurons in the CNS evaluate sensory information and decide on action, they stimulate efferent neurons. Efferent neurons (also called motor neurons) carry signals from the gray matter of the central nervous system through the nerves of the peripheral nervous system to effector cells. The effector may be cardiac or skeletal muscle tissue or glandular tissue. The effector then releases a hormone or moves a body part to respond to the stimulus.

Divisions of the nervous system

CNS - central
The spinal cord and brain together form the central nervous system, or CNS. The CNS acts as the body's control center, providing its processing, memory and regulatory systems. The central nervous system is involved in all conscious and subconscious collection of sensory information from the body's sensory receptors in order to remain aware of the body's internal and external conditions. Using this sensory information, it makes decisions about what conscious and subconscious actions to take to maintain the body's homeostasis and ensure its survival. The CNS is also responsible for higher nervous system functions such as language, creativity, expression, emotion, and personality. The brain is the seat of consciousness and determines who we are as people.

Peripheral nervous system
It (PNS) includes all parts of the nervous system outside the brain and spinal cord. These parts include all the cranial and spinal nerves, ganglia and sensory receptors.

Somatic nervous system
The SNS is a division of the PNS that includes all free efferent neurons. The SNS is the only consciously controlled part of the PNS and is responsible for stimulating the skeletal muscles in the body.

Autonomic nervous system
The ANS is a division of the PNS that includes all involuntary efferent neurons. It controls subconscious effectors such as visceral muscle tissue, cardiac muscle tissue and glandular tissue.

There are 2 divisions of the autonomic nervous system in the body: the sympathetic and parasympathetic divisions.

Sympathetic.
The sympathetic division forms the body's "fight or flight" response to stress, danger, excitement, exercise, emotion, and embarrassment. The sympathetic division increases breathing and heart rate, releases adrenaline and other stress hormones, and decreases digestion to cope with these situations.

Parasympathetic.
The parasympathetic region produces a rest response when the body is relaxed or at rest. The parasympathetic division works to override the sympathetic division after a stressful situation. Other functions of the parasympathetic division include decreasing breathing and heart rate, increasing digestion, and allowing the elimination of waste.
Enteric nervous system
The ENS is a division of the ANS that is responsible for regulating digestion and the functions of the digestive organs.
The ENS receives signals from the central nervous system through the sympathetic and parasympathetic divisions of the ANS system to help regulate its functions. However, the ENS generally operates independently of the central nervous system and continues to function without any external influence. For this reason, the ENS is often called the "second brain." The ENS is a huge system; there are almost as many neurons in the ENS as there are in the spinal cord.

Action potentials

Neurons function through the generation and propagation of electrochemical signals known as action potentials (APs). The hotspot is created by the movement of sodium and potassium ions across the neuronal membrane.

Resting potential.
At rest, neurons maintain the concentration of sodium ions regardless of the concentration of potassium ions inside the cell. This concentration is maintained by the cell membrane's sodium-potassium pump, which forces 3 sodium ions out of the cell for every 2 potassium ions entering the chamber. The ion concentration results in a residual electrical potential of 70 millivolts (mV), which means that there is a negative charge inside the cell compared to the surrounding environment.

Threshold potential.
If the signal allows enough positive ions to accumulate to enter the cell region and cause it to reach -55 mV, then the cell region will allow sodium ions to diffuse into the cell. - 55 MV threshold potential for neurons, as this is the “trigger” voltage they must reach to cross the threshold in forming an action potential.

Depolarization.
Sodium carries a positive charge, which causes the cell to depolarize from its normal negative charge. The voltage to depolarize all neurons is +30 mV. Depolarization of the cell is the access point that is transmitted along the neuron as a nerve signal. Positive ions spread to neighboring regions of the cell, initiating a new hotspot in those regions where they reach -55 mV. The impulse continues to travel down the neuron's cell membrane until it reaches the end of the axon.

Repolarization.
Once the depolarization voltage of +30 mV is reached, voltage-gated potassium ion channels become open, allowing positive potassium ions to diffuse out of the cell. The loss of potassium along with the pumping of sodium ions back out of the chamber through the sodium-potassium pump restores the cell to a resting potential of -55 mV. At this point, the neuron is ready to begin a new action potential.

Synapse

A synapse is a node between a neuron and another cell. Synapses can form between 2 neurons or between a neuron and an effector cell. There are two types of synapses found in the body: chemical synapses and electrical synapses.

Chemical synapses.
At the end of the neuron is an area known as the axon. The axon is separated from the next cell by a small gap known as the synaptic cleft. When the signal reaches the axon, it opens voltage-gated calcium ion channels. Calcium ions cause vesicles containing chemicals known as neurotransmitters to release their contents by exocytosis into the synaptic cleft. NT molecules cross the synaptic cleft and bind to receptor molecules on the cell, forming synapses with the neuron. These receptor molecules open ion channels that can either stimulate the cell receptor to form a new action potential or can inhibit the cell from forming an action potential when stimulated by another neuron.

Electrical synapses.
Electrical synapses form when 2 neurons are connected by small holes called gap junctions. A gap in the connection allows electrical current to pass from one neuron to another, so that the signal from one chamber is transmitted directly to another cell through the synapse.
Myelination
The axons of many neurons are covered with a coating known as myelin to increase the speed of nerve conduction throughout the body. Myelin is formed by 2 types of glial cells: Schwann cells in the PNS and oligodendrocytes in the central nervous system. In both cases, glial cells are wrapped in their plasma membrane around the axon many times to form a thick coating of lipids. The development of these myelin sheaths is known as myelination.

Myelination speeds up the movement of impulses in axons. The process of myelination begins with the acceleration of nerve conduction during fetal development and continues into early adulthood. Myelinated axons turn white due to the presence of lipids. They form the white matter of the brain, internal and external spinal cord. White matter is specialized for carrying information quickly through the brain and spinal cord. The gray matter of the brain and spinal cord are unmyelinated integration centers where information is processed.

Reflexes

Reflexes are quick, involuntary reactions in response to stimuli. The most well-known reflex is the patellar reflex, which is tested when a doctor taps a patient's knee during a physical examination. Reflexes are integrated in the gray matter of the spinal cord or brain stem. Reflexes allow the body to respond to stimuli very quickly, sending responses to effectors before nerve signals reach the conscious part of the brain. This explains why people often pull their hands away from a hot object before they realize they are in danger.

Functions of cranial nerves
Each of the 12 cranial nerves has a specific function within the nervous system.
The olfactory nerve (I) carries odor information to the brain from the olfactory epithelium in the roof of the nasal cavity.
The optic nerve (II) transmits visual information from the eyes to the brain.
The oculomotor, trochlear, and abducens nerves (III, IV, and VI) all work together to allow the brain to control eye movement and focusing. The trigeminal nerve (V) carries sensations from the face and innervates the muscles of mastication.
The facial nerve (VII) innervates the facial muscles to make facial expressions and carries taste information from the anterior 2/3 of the tongue.
The vestibulocochlear nerve (VIII) carries auditory information from the ears to the brain.

The glossopharyngeal nerve (IX) carries taste information from the posterior 1/3 of the tongue and aids in swallowing.

The vagus nerve (X), called the vagus nerve because it supplies many different areas, travels through the head, neck, and torso. It carries information about the state of vital organs in the brain, provides motor signals for speech control, and provides parasympathetic signals to many organs.

The accessory nerve (XI) controls movements of the shoulders and neck.

The hypoglossal nerve (XII) moves the tongue for speech and swallowing.

Sensory physiology

All sensory receptors can be classified according to their structure and the type of stimulation they detect. Structurally, there are 3 classes of sensory receptors: free, encapsulated nerve endings, and specialized cells.
Free nerve endings are simply free dendrites at the end of a neuron that extend into the tissue. Pain, heat and cold are all felt through free nerve endings. Encapsulated are free nerve endings wrapped in round capsules of connective tissue. When the capsule is deformed by touch or pressure, the neuron is excited to send signals to the central nervous system. Specialized cells detect stimuli from 5 special senses: vision, hearing, balance, smell and taste. Each of the special senses has its own unique sensory cells, such as the rods and cones in the retina for detecting light in the organs of vision.

Functionally, there are 6 main classes of receptors: mechanoreceptors, nociceptors, photoreceptors, chemoreceptors, osmoreceptors and thermoreceptors.

Mechanoreceptors.
Mechanoreceptors are sensitive to mechanical stimuli such as touch, pressure, vibration, and blood pressure.

Nociceptors.
Nociceptors respond to stimuli such as extreme heat, cold, or tissue damage by sending pain signals to the central nervous system.

Photoreceptors.
The photoreceptors in the retina are designed to detect light to provide the sense of vision.

Chemoreceptors.
Chemoreceptors are receptors for detecting chemicals in the blood and provide the senses of taste and smell.

Osmoreceptors.
Osmoreceptors are capable of monitoring blood osmolarity to determine the body's hydration level.

Thermoreceptors.
Thermoreceptors are receptors for detecting temperature inside and around the body.

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 the environment. All intellectual and creative activity also belongs 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 of the 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 covered topics such as “Types of the human nervous system” and “How the nervous system works,” but there are many interesting facts left aside that are worthy of mention:

1. The amount in our body is greater than the number of people on the entire planet Earth.
2. The brain contains about 90–100 billion neurons. If you connect them all into one line, it will reach about 1 thousand km.
3. The speed of the pulses reaches almost 300 km/h.
4. After the onset of puberty, the mass of the thinking organ increases every year decreases by approximately one gram.
5. Men's brains are approximately 1/12 larger than women's.
6. The largest organ of thinking was recorded in a mentally ill person.
7. The cells of the central nervous system are practically irreparable, and severe stress and anxiety can seriously reduce their number.
8. 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%.
9. 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.
10. 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.

Among many types of cells, these are the most difficult to restore, and some of their subtypes cannot be restored at all. That is why they are perfectly protected by the skull and vertebral bones.

It is also interesting that NS diseases are the least treatable. Modern medicine is mainly only capable of slowing down cell death, but it is impossible to stop this process. Many other types of cells can be protected from destruction for many years with the help of special drugs - for example, liver cells. At this time, epidermal (skin) cells are able to regenerate in a matter of days or weeks to their previous state.

Nervous system - spinal cord (8th grade) - biology, preparation for the Unified State Exam and the Unified State Exam

Human nervous system. Structure and functions

Conclusion

Absolutely every movement, every thought, glance, sigh and heartbeat - all this is controlled by a network of nerves. It is responsible for human interaction with the outside world and connects all other organs into a single whole - the body.

The structure and functions of the human nervous system are so complex that a separate section of anatomy called neuroanatomy is devoted to their study. The central nervous system is responsible for everything, for human life itself - and this is not an exaggeration. If there is a deviation in the functional activity of one of the departments, the integrity of the system is violated, and human health is at risk.

The nervous system is a collection of anatomically and functionally interconnected nerve cells with their processes. There are central and peripheral nervous systems. The central nervous system includes the brain and spinal cord, the peripheral nervous system includes the cranial and spinal nerves and their associated roots, spinal nodes and plexuses.

The main function of the nervous system is to regulate the vital functions of the body, maintain a constant internal environment, metabolic processes, and communicate with the outside world.

The nervous system consists of nerve cells, nerve fibers and neuroglial cells.

You will learn more about the structure and functions of the nervous system from this article.

Neuron as a structural and functional unit of the human nervous system

A nerve cell - neuron - is a structural and functional unit of the nervous system. A neuron is a cell that can perceive irritation, become excited, produce nerve impulses and transmit them to other cells.

That is, a neuron of the nervous system performs two functions:

1. Processes information received by it and transmits a nerve impulse
2. Maintains its vital functions

A neuron as a structural unit of the nervous system consists of a body and processes - short, branching ones (dendrites) and one long one (axon), which can give rise to numerous branches. The point of contact between neurons is called a synapse. Synapses can be between an axon and a nerve cell body, an axon and a dendrite, two axons, and less commonly, between two dendrites. At synapses, impulses are transmitted bioelectrically or through chemically active mediator substances (acetylcholine, norepinephrine, dopamine, serotonin, etc.). Numerous neuropeptides (enkephalins, endorphins, etc.) also participate in synaptic transmission.

Transportation of biologically active substances along the axon from the neuron body in the central nervous system to the synapse and back (axonal transport) ensures the supply and renewal of mediators, as well as the formation of new processes - axons and dendrites. Thus, two interconnected processes are constantly going on in the brain - the emergence of new processes and synapses and the partial disintegration of existing ones. And this underlies learning, adaptation, as well as restoration and compensation of impaired functions.

The cell membrane (cell membrane) is a thin lipoprotein plate penetrated by channels through which K, Na, Ca, C1 ions are selectively released. The functions of the cell membrane of the human nervous system are the creation of an electrical charge of the cell, due to which excitation and impulse arise.

Neuroglia is a connective tissue supporting structure of the nervous system (stroma) that performs a protective function.

The interweaving of axons, dendrites and processes of glial cells creates a picture of the neuropil.

A nerve fiber in the structure of the nervous system is a process of a nerve cell (axial cylinder), covered to a greater or lesser extent with myelin and surrounded by a Schwann membrane, which performs protective and trophic functions. In myelinated fibers, the impulse moves at speeds of up to 100 m/sec.

The accumulation of neuron cell bodies in the human nervous system forms the gray matter of the brain, and their processes form the white matter. A collection of neurons located outside the central nervous system is called a ganglion. A nerve is a trunk of united nerve fibers. Depending on the function, motor, sensory, autonomic and mixed nerves are distinguished.

Speaking about the structure of the human nervous system, the set of neurons that regulate any function is called the nerve center. The complex of physiological mechanisms associated with the performance of a specific function is called a functional system.

It includes cortical and subcortical nerve centers, pathways, peripheral nerves, and executive organs.

The functional activity of the nervous system is based on a reflex. A reflex is the body's response to stimulation. The reflex is carried out through a chain of neurons (at least two), called a reflex arc. The neuron that perceives irritation is the afferent part of the arc; the neuron that carries out the response is the efferent part. But the reflex act does not end with a one-time response from the working organ. There is a feedback loop that affects muscle tone - a self-regulatory ring in the form of a gamma loop.

The reflex activity of the nervous system ensures that the body perceives any changes in the external world.

The ability to perceive external phenomena is called reception. Sensitivity is the ability to sense stimuli perceived by the nervous system. Formations of the central and peripheral nervous system that perceive and analyze information about phenomena both inside the body and in the environment are called analyzers. There are visual, auditory, gustatory, olfactory, sensitive and motor analyzers. Each analyzer consists of a peripheral (receptor) section, a conductive part and a cortical section, in which the analysis and synthesis of perceived stimuli occurs.

Since the central sections of various analyzers are located in the cerebral cortex, all information coming from the external and internal environment is concentrated in it, which is the basis for mental higher nervous activity. Analysis of the information received by the cortex is recognition, gnosis. The functions of the cerebral cortex also include the development of action plans (programs) and their implementation - praxis.

The following describes how the spinal cord of the human nervous system works.

Human central nervous system: how the spinal cord works (with photo)

The spinal cord, as part of the central nervous system, is a cylindrical cord 41-45 cm long, located in the spinal canal from the first cervical vertebra to the second lumbar. It has two thickenings - cervical and lumbosacral, providing innervation to the limbs. The lumbosacral thickening passes into the medullary cone, ending in a filament-like continuation - the terminal filament, reaching the end of the spinal canal. The spinal cord performs conductor and reflex functions.

The spinal cord of the nervous system has a segmental structure. A segment is a section of the spinal cord with two pairs of spinal roots. In total, the spinal cord has 31-32 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1-2 coccygeal (vestigial). The anterior and posterior horns of the spinal cord, anterior and posterior spinal roots, spinal ganglia and spinal nerves make up the segmental apparatus of the spinal cord. As the spine develops, it becomes longer than the spinal cord, so the roots become longer and form a cauda equina.

In a section through the spinal cord of the human nervous system, gray and white matter can be seen. The gray matter consists of cells, has the shape of the letter “H” with the anterior - motor horns, the posterior - sensitive and the lateral - vegetative. The central canal of the spinal cord runs through the center of the gray matter. The spinal cord is divided into left and right halves, connected by the white and gray interconnections, through the median fissure (in front) and the median sulcus (at the back).

The gray matter is surrounded by nerve fibers - conductors, forming the white matter, in which anterior, lateral and posterior columns are distinguished. The front pillars are located between the front horns, the rear ones - between the rear ones, the lateral ones - between the front and rear horns of each side.

These photos show the structure of the spinal cord of the human nervous system:

Spinal nerves as part of the nervous system

Spinal nerves as part of the human nervous system are formed by the fusion of the anterior (motor) and posterior (sensory) roots of the spinal cord and exit the spinal canal through the intervertebral foramina. Each pair of these nerves innervates a specific area of ​​the body - a metamer.

Leaving the spinal canal, the spinal nerves of the nervous system are divided into four branches:

1. Front, innervating the skin and muscles of the limbs and the anterior surface of the body;
2. Rear, innervating the skin and muscles of the posterior surface of the body;
3. Meningeal, heading to the dura mater of the spinal cord;
4. Connecting, next to the sympathetic nodes.

Anterior branches Spinal nerves form plexuses: cervical, brachial, lumbar, sacral and coccygeal.

Cervical plexus formed by the anterior branches of the cervical nerves C:-C4; innervates the skin of the back of the head, the lateral surface of the face, the supra-, subclavian and superior scapular regions, and the diaphragm.

Brachial plexus formed by the anterior branches of C4-T1; innervates the skin and muscles of the upper limb.

Anterior branches T2-T11, without forming a plexus, together with the posterior branches provide innervation to the skin and muscles of the chest, back and abdomen.

Lumbosacral plexus is a combination of the lumbar and sacral.

Lumbar plexus formed by the anterior branches of T12–L 4; innervates the skin and muscles of the lower abdomen, the anterior and lateral surface of the thigh.

Sacral plexus formed by the anterior branches of the L5-S4 nerves; innervates the skin and muscles of the gluteal region, perineum, posterior thigh, lower leg and foot. The largest nerve in the body, the sciatic, departs from it.

Coccygeal plexus formed by the anterior branches of S5-C0C2; innervates the perineum.

The next section of the article is devoted to the structure and functions of the main parts of the brain.

Human nervous system: structure and functions of the main parts of the brain

The brain, which is part of the nervous system, is located in the cranium, covered with meninges, between which cerebrospinal fluid (CSF) circulates. The brain is connected to the spinal cord through the foramen magnum. The weight of the adult human brain is on average 1300-1500 g. The function of the human brain is to regulate all processes occurring in the body.

The brain as part of the nervous system consists of the following sections: two hemispheres, the cerebellum and the brainstem.

The brainstem consists of the medulla oblongata, pons, cerebral peduncles (midbrain), as well as the base and tegmentum.

The medulla oblongata is a continuation of the spinal cord. The conventional border of the medulla oblongata and the spinal cord is the intersection of the pyramidal tracts. The medulla oblongata contains vital centers that regulate breathing, blood circulation, and swallowing; it contains all the motor and sensory pathways connecting the spinal cord and brain.

The structure of the bridge of the nervous system of the brain includes the nuclei of the V, VI, VII and VIII pairs of cranial nerves, sensory pathways in the medial lemniscus, fibers of the auditory tract in the form of the lateral lemniscus, etc.

The cerebral peduncles are part of the midbrain; they connect the pons to the hemispheres and include ascending and descending pathways. The roof of the midbrain has a plate on which the quadrigemina is located. The primary subcortical center of vision is located in the superior colliculi, and the primary subcortical hearing center is located in the inferior colliculi. Thanks to the mounds, the body’s indicative and protective reactions occur under the influence of visual and auditory stimuli. Under the roof of the midbrain is the midbrain aqueduct, which connects the third and fourth ventricles of the cerebral hemispheres.

The diencephalon consists of the thalamus (optic thalamus), epithalamus, metathalamus and hypothalamus. The cavity of the diencephalon is the third ventricle. The thalamus is a collection of nerve cells located on both sides of the third ventricle. The thalamus is one of the subcortical centers of vision and the center of afferent impulses from throughout the body, sent to the cerebral cortex. In the thalamus, sensations are formed and impulses are transmitted to the extra-pyramidal system.

The metathalamus, as part of the brain of the human nervous system, also contains one of the subcortical centers of vision and the subcortical center of hearing (medial and lateral geniculate body).

The epithalamus includes the pineal gland, which is an endocrine gland that regulates the function of the adrenal cortex and the development of sexual characteristics.

The hypothalamus consists of the gray tubercle, infundibulum, medullary appendage (neurohypophysis) and paired mastoid bodies. The hypothalamus contains accumulations of gray matter in the form of nuclei, which are centers of the autonomic nervous system that regulate all types of metabolism, respiration, blood circulation, the activity of internal organs and endocrine glands. The hypothalamus maintains a constant internal environment in the body (homeostasis) and, thanks to connections with the limbic system, participates in the formation of emotions, providing their vegetative coloring.

Along the entire length of the brain stem, a phylogenetically ancient formation of gray matter is located and occupies a central position in the form of a dense network of nerve cells with many processes - the reticular formation. Branches from all types of sensory systems are directed to the reticular formation, so any irritation coming from the periphery is transmitted along ascending pathways to the cerebral cortex, activating its activity. Thus, the reticular formation is involved in the implementation of normal biological rhythms of wakefulness and sleep, and is an ascending, activating system of the brain - an “energy generator.”

Together with the limbic structures, the reticular formation ensures normal cortical-subcortical relationships and behavioral reactions. It is also involved in the regulation of muscle tone, and its descending pathways provide reflex activity of the spinal cord.

The cerebellum is located under the occipital lobes of the brain and is separated from them by the dura mater - the cerebellar tentorium. It is divided into a central part - the cerebellar vermis and lateral sections - the hemispheres. In the depths of the white matter of the cerebellar hemispheres there are the dentate nucleus and smaller nuclei - cortical and spherical. The roof nucleus is located in the middle part of the cerebellum. The cerebellar nuclei are involved in the coordination of movements and balance, as well as in the regulation of muscle tone. Three pairs of legs connect the cerebellum with all parts of the brain stem, providing its connection with the extrapyramidal system, cerebral cortex and spinal cord.

The structure and main functions of the cerebral hemispheres

The structure of the cerebrum includes two hemispheres connected to each other by the large white commissure - the corpus callosum, consisting of fibers connecting the lobes of the brain of the same name. The surface of each hemisphere is covered with a cortex consisting of cells and divided by many grooves. The areas of the cortex located between the grooves are called gyri. The deepest grooves divide each hemisphere into lobes: frontal, parietal, occipital and temporal. The central (Rolandic) sulcus separates the parietal lobe from the frontal lobe; in front of it is the precentral gyrus. Horizontal grooves divide the frontal lobe into superior, middle and inferior gyri.

Behind the central sulcus in the structure of the cerebral hemispheres is the postcentral gyrus. The parietal lobe is divided by the transverse intraparietal sulcus into the superior and inferior parietal lobes.

The deep lateral (Sylvian) fissure separates the temporal lobe from the frontal and parietal lobes. On the lateral surface of the temporal lobe, the superior, middle and inferior temporal gyri are located longitudinally. On the inner surface of the temporal lobe is a gyrus called the hippocampus.

On the inner surface of the hemispheres, the parieto-occipital sulcus separates the parietal lobe from the occipital lobe, and the calcarine sulcus divides the occipital lobe into two gyri - the precuneus and the cuneus.

On the medial surface of the hemispheres above the corpus callosum, the cingulate gyrus is located in an arcuate manner, passing into the parahippocampal gyrus.

The cerebral cortex is the youngest part of the central nervous system in evolutionary terms, consisting of neurons. It is most developed in humans. The cortex is a layer of gray matter 1.3-4 mm thick, covering the white matter of the hemispheres, consisting of axons, dendrites of nerve cells and neuroglia.

The cortex plays a very important role in the regulation of vital processes in the body, the implementation of behavioral acts and mental activity.

The function of the frontal lobe cortex is to organize movements, speech motor skills, complex forms of behavior and thinking. The center of voluntary movements is located in the precentral gyrus, and the pyramidal tract begins from here.

The parietal lobe contains the centers of the analyzer of general sensitivity, gnosis, praxis, writing, and counting.

The functions of the temporal lobe of the cerebrum are the perception and processing of auditory, taste and olfactory sensations, analysis and synthesis of speech sounds, and memory mechanisms. The basal sections of the cerebral hemispheres are connected with the higher autonomic centers.

The occipital lobe contains the cortical centers of vision.

Not all functions of the cerebral hemispheres are represented symmetrically in the cortex. For example, speech, reading and writing are functionally associated with the left hemisphere for most people.

The right hemisphere provides orientation in time, place, and is associated with the emotional sphere.

The axons and dendrites of the nerve cells of the cortex constitute pathways that connect various parts of the cortex, the cortex and other parts of the brain and spinal cord. The pathways form the corona radiata, consisting of fan-shaped diverging fibers, and the internal capsule, located between the basal (subcortical) nuclei.

The subcortical nuclei (caudate, lenticular, amygdala, fence) are located deep in the white matter around the ventricles of the brain. Morphologically and functionally, the caudate nucleus and putamen are combined into the striatum (striatum). The globus pallidus, red nucleus, substantia nigra and reticular formation of the midbrain are combined into the pallidum (pallidum). The striatum and pallidum form a very important functional system - striopallidal or extrapyramidal. The extrapyramidal system ensures the preparation of various muscle groups to perform integral movements, also provides facial, auxiliary and friendly movements, gestures, automated motor acts (grimaces, whistling, etc.).

A special role is played by the most ancient in evolutionary terms sections of the cerebral cortex, located on the inner surface of the hemispheres - the cingulate and parahippocampal gyri. Together with the amygdala, olfactory bulb and olfactory tract, they form the limbic system, which is closely connected with the reticular formation of the brain stem and constitutes a single functional system - the limbic-reticular complex (LRK). Speaking about the structure and functions of the cerebrum, it should be noted that the limbic-reticular complex is involved in the formation of instinctive and emotional reactions (food, sexual, defensive instincts, anger, rage, pleasure) of human behavior. The LRC also takes part in the regulation of the tone of the cerebral cortex, the processes of sleep, wakefulness, and adaptation.

See how the large brain of the human nervous system works in these photos:

12 pairs of cranial nerves of the nervous system and their functions (with video)

At the base of the brain, 12 pairs of cranial nerves emerge from the medulla. Based on their function, they are divided into sensory, motor and mixed. Proximally, the cranial nerves are connected to the brainstem nuclei, subcortical nuclei, cerebral cortex and cerebellum. Distally, the cranial nerves are connected to various functional structures (eyes, ears, facial muscles, tongue, glands, etc.).

I pair - olfactory nerve ( n. olfactorius) . The receptors are located in the mucous membrane of the nasal concha, connected to the sensitive neurons of the olfactory bulb. Along the olfactory tract, signals enter the primary olfactory centers (nuclei of the olfactory triangle) and then to the internal parts of the temporal lobe (hippocampus), where the cortical centers of smell are located.

II pair - optic nerves ( n. opticus) . The receptors of this pair of cranial nerves are the cells of the retina, from the ganglion layer of which the nerves themselves begin. Passing at the base of the frontal lobes in front of the sella turcica, the optic nerves partially cross, forming a chiasm, and are sent as part of the visual tracts to the subcortical visual centers, and from them to the occipital lobes.

III pair - oculomotor nerves ( n. oculomotorius) . They contain motor and parasympathetic fibers that innervate the muscles that elevate the upper eyelids, constrict the pupil, and the muscles of the eyeball, with the exception of the superior oblique and abductor muscles.

IV pair - trochlear nerves ( n. trochlearis) . This pair of cranial nerves innervates the superior oblique muscles of the eyes.

V pair - trigeminal nerves ( n. trigeminus) . They are mixed nerves. Sensitive neurons of the trigeminal (Gasserian) ganglion form three large branches: the ophthalmic, maxillary and mandibular nerves, which emerge from the cranial cavity and innervate the frontoparietal part of the scalp, facial skin, eyeballs, mucous membranes of the nasal cavities, mouth, anterior two-thirds of the tongue, teeth, dura mater. The central processes of the cells of the Gasserian ganglion go deep into the brain stem and connect with second sensory neurons, forming a chain of nuclei. Signals from the brainstem nuclei pass through the thalamus to the postcentral gyrus (fourth neuron) of the opposite hemisphere. Peripheral innervation corresponds to the branches of the nerve, segmental innervation has the form of ring zones. Motor fibers of the trigeminal nerve regulate the functioning of the masticatory muscles.

VI pair - abducens nerves ( n. abducens) . Innervates the abductor muscles of the eye.

VII pair - facial nerves ( n. facialis) . Innervates the facial muscles. When leaving the pons, the intermediate nerve joins the facial nerve, providing taste innervation to the anterior two-thirds of the tongue, parasympathetic innervation of the submandibular and sublingual glands, and lacrimal glands.

VIII pair - cochleovestibular (auditory, vestibulocochlear) nerve ( n. vestibulo-cochlearis) . This pair of cranial nerves ensures the function of hearing and balance, and have extensive connections with the structures of the extrapyramidal system, cerebellum, spinal cord, and cortex.

IX pair - glossopharyngeal nerves ( n. glossopharyngeus).

They function in close connection with the X-pair - the vagus nerves ( n. vagus) . These nerves have a number of common nuclei in the medulla oblongata that perform sensory, motor and secretory functions. They innervate the soft palate, pharynx, upper esophagus, parotid salivary gland, and posterior third of the tongue. The vagus nerve provides parasympathetic innervation of all internal organs to the level of the pelvis.

XI pair - accessory nerves ( n. accessorius) . Innervates the sternocleidomastoid and trapezius muscles.

XII pair - hypoglossal nerves ( n. hypoglossus) . Innervates the muscles of the tongue.

Autonomic division of the human nervous system: structure and main functions

Autonomic nervous system (ANS)- This is part of the nervous system that ensures the vital functions of the body. It innervates the heart, blood vessels, internal organs, and also carries out tissue trophism and ensures the constancy of the internal environment of the body. In the autonomic part of the nervous system, there are sympathetic and parasympathetic parts. They interact as antagonists and synergists. Thus, the sympathetic nervous system dilates the pupil, increases the frequency of heart contractions, constricts blood vessels, increases blood pressure, reduces the secretion of glands, slows down the peristalsis of the stomach and intestines, and contracts the sphincters. Parasympathetic, on the contrary, constricts the pupil, slows the heartbeat, dilates blood vessels, lowers blood pressure, increases the secretion of glands and intestinal motility, and relaxes the sphincters.

The sympathetic autonomic nervous system carries out a trophic function, enhances oxidative processes, nutrient consumption, respiratory and cardiovascular activity, and changes the permeability of the cell membrane. The role of the parasympathetic system is protective. In a state of rest, the vital activity of the body is ensured by the parasympathetic system, and during stress - by the sympathetic system.

In the structure of the autonomic nervous system, segmental and suprasegmental sections are distinguished.

The segmental part of the ANS is represented by sympathetic and parasympathetic formations at the spinal and brain stem level.

The centers of the human sympathetic autonomic nervous system are located in the lateral columns of the spinal cord at the level of C8-L3. Sympathetic fibers exit the spinal cord with the anterior roots, are interrupted in the nodes of the paired sympathetic trunk, which is located on the anterior surface of the spinal column and consists of 20-25 pairs of nodes, containing sympathetic cells. Fibers depart from the nodes of the sympathetic trunk, forming sympathetic plexuses and nerves that are directed to organs and vessels.

The centers of the parasympathetic nervous system are located in the brain stem and in the sacral segments S2-S4 of the spinal cord. The processes of cells of the parasympathetic nuclei of the brain stem as part of the oculomotor, facial, glossopharyngeal and vagus nerves provide innervation of the glands and smooth muscles of all internal organs, with the exception of the pelvic organs. The fibers of the cells of the parasympathetic nuclei of the sacral segments form the pelvic splanchnic nerves going to the bladder, rectum, and genitals.

Both sympathetic and parasympathetic fibers are interrupted in the peripheral autonomic ganglia located near the innervated organs or in their walls.

The fibers of the autonomic nervous system form a number of plexuses: solar, pericardial, mesenteric, pelvic, which innervate the internal organs and regulate their function.

The higher suprasegmental division of the autonomic nervous system includes the nuclei of the hypothalamus, the limbic-reticular complex, the basal structures of the temporal lobe and some parts of the associative zone of the cerebral cortex. The role of these formations is to integrate basic mental and somatic functions.

In a state of rest, the vital activity of the body is ensured by the parasympathetic system, and during stress - by the sympathetic system.

The centers of the sympathetic nervous system are located in the lateral columns of the spinal cord at the level of C8-L3; sympathetic fibers exit the spinal cord with the anterior roots and are interrupted at the nodes of the paired sympathetic trunk.

Here you can watch the video “The Human Nervous System” to better understand how it works:

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Useful articles

Subject. Structure and functions of the human nervous system

1 What is the nervous system

2 Central nervous system

Brain

Spinal cord

CNS

3 Autonomic nervous system

4 Development of the nervous system in ontogenesis. Characteristics of the three-vesicle and five-vesicle stages of brain formation

What is the nervous system

Nervous system is a system that regulates the activities of all human organs and systems. This system provides:

1) functional unity of all human organs and systems;

2) the connection of the whole organism with the environment.

Nervous system controls the activities of various organs, systems and apparatuses that make up the body. It regulates the functions of movement, digestion, respiration, blood supply, metabolic processes, etc. The nervous system establishes the relationship of the body with the external environment, unites all parts of the body into a single whole.

The nervous system is divided according to topographic principle into central and peripheral ( rice. 1).

central nervous system(CNS) includes the brain and spinal cord.

TO peripheral part of the nervoussystems include spinal and cranial nerves with their roots and branches, nerve plexuses, nerve ganglia, and nerve endings.

In addition, the nervous system containstwo special parts : somatic (animal) and vegetative (autonomous).

Somatic nervous system innervates primarily the organs of the soma (body): striated (skeletal) muscles (face, torso, limbs), skin and some internal organs (tongue, larynx, pharynx). The somatic nervous system primarily carries out the functions of connecting the body with the external environment, providing sensitivity and movement, causing contraction of skeletal muscles. Since the functions of movement and feeling are characteristic of animals and distinguish them from plants, this part of the nervous system is calledanimal(animal). The actions of the somatic nervous system are controlled by human consciousness.

Autonomic nervous system innervates the insides, glands, smooth muscles of organs and skin, blood vessels and the heart, regulates metabolic processes in tissues. The autonomic nervous system influences the processes of so-called plant life, common to animals and plants(metabolism, respiration, excretion, etc.), which is where its name comes from ( vegetative- vegetable).

Both systems are closely related, but the autonomic nervous system has some degree of independence and does not depend on our will, as a result of which it is also called autonomic nervous system.

She is being divided into two parts sympathetic And parasympathetic. The identification of these departments is based both on an anatomical principle (differences in the location of centers and the structure of the peripheral parts of the sympathetic and parasympathetic nervous system) and on functional differences.

Stimulation of the sympathetic nervous system promotes intense activity of the body; parasympathetic stimulation , on the contrary, helps restore the resources expended by the body.

The sympathetic and parasympathetic systems have opposite effects on many organs, being functional antagonists. Yes, under influence of impulses coming along the sympathetic nerves, heart contractions become more frequent and intensified, blood pressure in the arteries increases, glycogen is broken down in the liver and muscles, the glucose content in the blood increases, the pupils dilate, the sensitivity of the sensory organs and the performance of the central nervous system increases, the bronchi narrow, contractions of the stomach and intestines are inhibited, secretion decreases gastric juice and pancreatic juice, the bladder relaxes and its emptying is delayed. Under the influence of impulses coming through the parasympathetic nerves, heart contractions slow down and weaken, blood pressure decreases, blood glucose levels decrease, contractions of the stomach and intestines are stimulated, the secretion of gastric juice and pancreatic juice increases, etc.

central nervous system

Central nervous system (CNS)- the main part of the nervous system of animals and humans, consisting of a collection of nerve cells (neurons) and their processes.

central nervous system consists of the brain and spinal cord and their protective membranes.

The outermost one is dura mater , underneath it is located arachnoid (arachnoid ), and then pia mater fused to the surface of the brain. Between the soft and arachnoid membranes there is subarachnoid space , containing cerebrospinal fluid, in which both the brain and spinal cord literally float. The action of the buoyant force of the fluid leads to the fact that, for example, the adult brain, which has an average mass of 1500 g, actually weighs 50–100 g inside the skull. The meninges and cerebrospinal fluid also play the role of shock absorbers, softening all kinds of shocks and shocks that tests the body and which could lead to damage to the nervous system.

The central nervous system is formed of gray and white matter .

Gray matter consist of cell bodies, dendrites and unmyelinated axons, organized into complexes that include countless synapses and serve as information processing centers, providing many functions of the nervous system.

White matter consists of myelinated and unmyelinated axons that act as conductors transmitting impulses from one center to another. The gray and white matter also contains glial cells.

CNS neurons form many circuits that perform two main functions: provide reflex activity, as well as complex information processing in higher brain centers. These higher centers, such as the visual cortex (visual cortex), receive incoming information, process it, and transmit a response signal along the axons.

The result of the activity of the nervous system- this or that activity, which is based on the contraction or relaxation of muscles or the secretion or cessation of secretion of glands. It is with the work of muscles and glands that any way of our self-expression is connected. Incoming sensory information is processed through a sequence of centers connected by long axons that form specific pathways, for example pain, visual, auditory. Sensitive (ascending) the pathways go in an ascending direction to the centers of the brain. Motor (descending) pathways connect the brain with motor neurons of the cranial and spinal nerves. The pathways are usually organized in such a way that information (for example, pain or tactile) from the right side of the body enters the left side of the brain and vice versa. This rule also applies to the descending motor pathways: the right half of the brain controls the movements of the left half of the body, and the left half controls the right. There are, however, a few exceptions to this general rule.

Brain

consists of three main structures: the cerebral hemispheres, the cerebellum and the brainstem.

Large hemispheres - the largest part of the brain - contain higher nerve centers that form the basis of consciousness, intelligence, personality, speech, and understanding. In each of the cerebral hemispheres, the following formations are distinguished: underlying isolated accumulations (nuclei) of gray matter, which contain many important centers; a large mass of white matter located above them; covering the outside of the hemispheres is a thick layer of gray matter with numerous convolutions that makes up the cerebral cortex.

Cerebellum also consists of a deep gray matter, an intermediate mass of white matter and an outer thick layer of gray matter, forming many convolutions. The cerebellum primarily provides coordination of movements.

Trunk The brain is formed by a mass of gray and white matter, not divided into layers. The trunk is closely connected with the cerebral hemispheres, the cerebellum and the spinal cord and contains numerous centers of sensory and motor pathways. The first two pairs of cranial nerves arise from the cerebral hemispheres, while the remaining ten pairs arise from the trunk. The trunk regulates vital functions such as breathing and blood circulation.

Scientists have calculated that a man's brain is heavier than a woman's brain by an average of 100 gm. They explain this by the fact that most men are much larger than women in their physical parameters, that is, all parts of a man’s body are larger than parts of a woman’s body. The brain actively begins to grow even when the child is still in the womb. The brain reaches its “true” size only when a person reaches twenty years of age. At the very end of a person's life, his brain becomes a little lighter.

The brain has five main sections:

1) telencephalon;

2) diencephalon;

3) midbrain;

4) hindbrain;

5) medulla oblongata.

If a person has suffered a traumatic brain injury, this always has a negative impact on both his central nervous system and his mental state.

The “pattern” of the brain is very complex. The complexity of this “pattern” is determined by the fact that furrows and ridges run along the hemispheres, which form a kind of “convolutions”. Despite the fact that this “pattern” is strictly individual, several common grooves are distinguished. Thanks to these common grooves, biologists and anatomists have identified 5 hemisphere lobes:

1) frontal lobe;

2) parietal lobe;

3) occipital lobe;

4) temporal lobe;

5) hidden share.

Despite the fact that hundreds of works have been written to study the functions of the brain, its nature has not been fully elucidated. One of the most important riddles that the brain “makes” is vision. Or rather, how and with what help we see. Many people mistakenly assume that vision is the prerogative of the eyes. This is wrong. Scientists are more inclined to believe that the eyes simply perceive signals that the environment around us sends us. The eyes transmit them further “up the chain of command.” The brain, having received this signal, builds a picture, i.e. we see what our brain “shows” us. The issue of hearing should be resolved similarly: it is not the ears that hear. Or rather, they also receive certain signals that the environment sends us.

Spinal cord.

The spinal cord looks like a cord; it is somewhat flattened from front to back. Its size in an adult is approximately 41 to 45 cm, and its weight is about 30 gm. It is “surrounded” by the meninges and is located in the medullary canal. Throughout its entire length, the thickness of the spinal cord is the same. But it has only two thickenings:

1) cervical thickening;

2) lumbar thickening.

It is in these thickenings that the so-called innervation nerves of the upper and lower extremities are formed. Dorsal brainis divided into several departments:

1) cervical region;

2) thoracic region;

3) lumbar region;

4) sacral section.

Located inside the spinal column and protected by its bone tissue, the spinal cord has a cylindrical shape and is covered with three membranes. In a cross section, the gray matter is shaped like the letter H or a butterfly. Gray matter is surrounded by white matter. Sensitive fibers of the spinal nerves end in the dorsal (posterior) parts of the gray matter - the dorsal horns (at the ends of the H, facing the back). The bodies of motor neurons of the spinal nerves are located in the ventral (anterior) parts of the gray matter - the anterior horns (at the ends of the H, distant from the back). In the white matter there are ascending sensory pathways ending in the gray matter of the spinal cord, and descending motor pathways coming from the gray matter. In addition, many fibers in the white matter connect different parts of the gray matter of the spinal cord.

Home and specific central nervous system function- implementation of simple and complex highly differentiated reflective reactions, called reflexes. In higher animals and humans, the lower and middle sections of the central nervous system - the spinal cord, medulla oblongata, midbrain, diencephalon and cerebellum - regulate the activity of individual organs and systems of a highly developed organism, carry out communication and interaction between them, ensure the unity of the organism and the integrity of its activities. The higher department of the central nervous system - the cerebral cortex and the nearest subcortical formations - mainly regulates the connection and relationship of the body as a whole with the environment.

Main structural features and functions CNS

connected to all organs and tissues through the peripheral nervous system, which in vertebrates includes cranial nerves emanating from the brain, and spinal nerves- from the spinal cord, intervertebral nerve nodes, as well as the peripheral part of the autonomic nervous system - nerve nodes, with nerve fibers approaching them (preganglionic) and extending from them (postganglionic).

Sensory or afferent nerves adductor fibers carry excitation to the central nervous system from peripheral receptors; by outlet efferent (motor and autonomic) nerve fibers send excitation from the central nervous system to the cells of the executive working apparatus (muscles, glands, blood vessels, etc.). In all parts of the central nervous system there are afferent neurons that perceive stimuli coming from the periphery, and efferent neurons that send nerve impulses to the periphery to various executive effector organs.

Afferent and efferent cells with their processes can contact each other and form two-neuron reflex arc, carrying out elementary reflexes (for example, tendon reflexes of the spinal cord). But, as a rule, intercalary nerve cells, or interneurons, are located in the reflex arc between the afferent and efferent neurons. Communication between different parts of the central nervous system is also carried out using many afferent, efferent and interneurons of these sections, forming intracentral short and long pathways. The CNS also includes neuroglial cells, which perform a supporting function in it and also participate in the metabolism of nerve cells.

The brain and spinal cord are covered with membranes:

1) dura mater;

2) arachnoid membrane;

3) soft shell.

Hard shell. The hard shell covers the outside of the spinal cord. In its shape it most closely resembles a bag. It should be said that the outer dura mater of the brain is the periosteum of the skull bones.

Arachnoid. The arachnoid membrane is a substance that is almost closely adjacent to the hard shell of the spinal cord. The arachnoid membrane of both the spinal cord and the brain does not contain any blood vessels.

Soft shell. The soft membrane of the spinal cord and brain contains nerves and vessels, which, in fact, nourish both brains.

Autonomic nervous system

Autonomic nervous system - This is one of the parts of our nervous system. The autonomic nervous system is responsible for: the activity of internal organs, the activity of endocrine and exocrine glands, the activity of blood and lymphatic vessels, and also, to some extent, the muscles.

The autonomic nervous system is divided into two sections:

1) sympathetic section;

2) parasympathetic section.

Sympathetic nervous system dilates the pupil, it also causes increased heart rate, increased blood pressure, dilates small bronchi, etc. This nervous system is carried out by sympathetic spinal centers. It is from these centers that the peripheral sympathetic fibers begin, which are located in the lateral horns of the spinal cord.

Parasympathetic nervous system is responsible for the activity of the bladder, genitals, rectum, and it also “irritates” a number of other nerves (for example, the glossopharyngeal, oculomotor nerve). This “diverse” activity of the parasympathetic nervous system is explained by the fact that its nerve centers are located both in the sacral part of the spinal cord and in the brain stem. Now it becomes clear that those nerve centers that are located in the sacral part of the spinal cord control the activity of organs located in the pelvis; nerve centers, which are located in the brain stem, regulate the activity of other organs through a number of special nerves.

How is the activity of the sympathetic and parasympathetic nervous system controlled? The activity of these sections of the nervous system is controlled by special autonomic apparatuses located in the brain.

Diseases of the autonomic nervous system. The causes of diseases of the autonomic nervous system are the following: a person does not tolerate hot weather well or, conversely, feels uncomfortable in winter. A symptom may be that when a person is excited, he quickly begins to blush or turn pale, his pulse quickens, and he begins to sweat profusely.

It should also be noted that diseases of the autonomic nervous system occur in people from birth. Many people believe that if a person gets excited and blushes, it means that he is simply too modest and shy. Few would think that this person has any disease of the autonomic nervous system.

These diseases can also be acquired. For example, due to a head injury, chronic poisoning with mercury, arsenic, or due to a dangerous infectious disease. They can also occur when a person is overworked, with a lack of vitamins, or with severe mental disorders and worries. Also, diseases of the autonomic nervous system can be the result of non-compliance with safety regulations in the workplace with hazardous working conditions.

The regulatory activity of the autonomic nervous system may be impaired. Diseases can “masquerade” as other diseases. For example, with a disease of the solar plexus, bloating and poor appetite may be observed; with a disease of the cervical or thoracic nodes of the sympathetic trunk, chest pain may be observed, which can radiate to the shoulder. Such pain is very similar to heart disease.

To prevent diseases of the autonomic nervous system, a person should follow a number of simple rules:

1) avoid nervous fatigue and colds;

2) observe safety precautions in production with hazardous working conditions;

3) eat well;

4) go to the hospital in a timely manner and complete the entire prescribed course of treatment.

Moreover, the last point, timely access to the hospital and complete completion of the prescribed course of treatment, is the most important. This follows from the fact that delaying your visit to the doctor for too long can lead to the most dire consequences.

Good nutrition also plays an important role, because a person “charges” his body and gives it new strength. Having refreshed yourself, the body begins to fight diseases several times more actively. In addition, fruits contain many beneficial vitamins that help the body fight disease. The most useful fruits are in their raw form, because when they are prepared, many beneficial properties may disappear. A number of fruits, in addition to containing vitamin C, also contain a substance that enhances the effect of vitamin C. This substance is called tannin and is found in quince, pears, apples, and pomegranate.

Development of the nervous system in ontogenesis. Characteristics of the three-vesicle and five-vesicle stages of brain formation

Ontogenesis, or the individual development of an organism, is divided into two periods: prenatal (intrauterine) and postnatal (after birth). The first lasts from the moment of conception and the formation of the zygote until birth; the second - from the moment of birth to death.

Prenatal period in turn, is divided into three periods: initial, embryonic and fetal. The initial (preimplantation) period in humans covers the first week of development (from the moment of fertilization to implantation into the uterine mucosa). The embryonic (prefetal, embryonic) period is from the beginning of the second week to the end of the eighth week (from the moment of implantation until the completion of organ formation). The fetal period begins in the ninth week and lasts until birth. At this time, increased growth of the body occurs.

Postnatal period Ontogenesis is divided into eleven periods: 1st - 10th day - newborns; 10th day - 1 year - infancy; 1-3 years - early childhood; 4-7 years - first childhood; 8-12 years old - second childhood; 13-16 years - adolescence; 17-21 years - adolescence; 22-35 years old - the first mature age; 36-60 years - second mature age; 61-74 years - old age; from 75 years old - old age, after 90 years old - long-livers.

Ontogenesis ends with natural death.

The nervous system develops from three main structures: neural tube, neural crest and neural placodes. The neural tube is formed as a result of neurulation from the neural plate, a section of ectoderm located above the notochord. According to the theory of Spemen's organizers, notochord blastomeres are capable of secreting substances - inductors of the first kind, as a result of which the neural plate bends into the body of the embryo and a neural groove is formed, the edges of which then merge, forming the neural tube. The closure of the edges of the neural groove begins in the cervical region of the body of the embryo, spreading first to the caudal part of the body, and later to the cranial part.

The neural tube gives rise to the central nervous system, as well as neurons and gliocytes of the retina. Initially, the neural tube is represented by a multirow neuroepithelium, the cells in it are called ventricular. Their processes, facing the cavity of the neural tube, are connected by nexuses; the basal parts of the cells lie on the subpial membrane. The nuclei of neuroepithelial cells change their location depending on the phase of the cell's life cycle. Gradually, towards the end of embryogenesis, ventricular cells lose the ability to divide and in the postnatal period give rise to neurons and various types of gliocytes. In some areas of the brain (germinal or cambial zones), ventricular cells do not lose their ability to divide. In this case, they are called subventricular and extraventricular. Of these, in turn, neuroblasts differentiate, which, no longer having the ability to proliferate, undergo changes during which they turn into mature nerve cells - neurons. The difference between neurons and other cells of their differon (cell series) is the presence in them of neurofibrils, as well as processes, with the axon (neurite) appearing first, and dendrites later. The processes form connections - synapses. In total, the differentiation of nervous tissue is represented by neuroepithelial (ventricular), subventricular, extraventricular cells, neuroblasts and neurons.

Unlike macroglial gliocytes, which develop from ventricular cells, microglial cells develop from mesenchyme and enter the macrophage system.

The cervical and trunk parts of the neural tube give rise to the spinal cord, the cranial part differentiates into the brain. The cavity of the neural tube turns into the spinal canal, connected to the ventricles of the brain.

The brain undergoes several stages in its development. Its sections develop from the primary brain vesicles. At first there are three of them: front, middle and diamond-shaped. By the end of the fourth week, the forebrain is divided into the rudiments of the telencephalon and diencephalon. Soon after this, the rhomboid vesicle also divides, giving rise to the hindbrain and medulla oblongata. This stage of brain development is called the five brain vesicle stage. The time of their formation coincides with the time of the appearance of the three bends of the brain. First of all, the parietal flexure is formed in the region of the middle cerebral vesicle, its convexity facing dorsally. After it, the occipital bend appears between the rudiments of the medulla oblongata and spinal cord. Its convexity is also facing dorsally. The last one to form is a bridge bend between the two previous ones, but it bends to the ventral side.

The cavity of the neural tube in the brain is transformed first into the cavities of three, then five vesicles. The cavity of the rhomboid vesicle gives rise to the fourth ventricle, which connects through the midbrain aqueduct (the cavity of the mesencephalon) with the third ventricle, formed by the cavity of the diencephalon rudiment. The cavity of the initially unpaired rudiment of the telencephalon is connected through the interventricular foramen with the cavity of the rudiment of the diencephalon. Subsequently, the cavity of the terminal bladder will give rise to the lateral ventricles.

The walls of the neural tube at the stages of formation of the brain vesicles will thicken most evenly in the region of the midbrain. The ventral part of the neural tube is transformed into the cerebral peduncles (midbrain), gray tubercle, infundibulum, and posterior lobe of the pituitary gland (diencephalon). Its dorsal part turns into the plate of the roof of the midbrain, as well as the roof of the third ventricle with the choroid plexus and the epiphysis. The lateral walls of the neural tube in the area of ​​the diencephalon grow, forming the visual thalamus. Here, under the influence of inductors of the second kind, protrusions are formed - eye vesicles, each of which will give rise to the optic cup, and later - the retina. Inductors of the third kind, located in the optic cups, influence the ectoderm above them, which is laced into the cups, giving rise to the lens.