CNS - what is it? Central nervous system: departments, functions

CNS - what is it? The structure of the human nervous system is described in the form of a branched electrical network. Perhaps, this is the most accurate metaphor from possible, since on thin threads-fibers the current really runs. Our cells themselves generate microdischarges in order to quickly deliver information from receptors and sensory organs to the brain. But the system does not function randomly, everything is subject to a strict hierarchy. That is why the central and peripheral nervous system is isolated .

Departments of the central nervous system

Let us consider this system in more detail. And yet, the central nervous system - what is it? Medicine gives an exhaustive answer to this question. This is the main part of the nervous system of chordates and humans. It consists of structural units - neurons. In invertebrates, this entire structure is similar to a cluster of nodules that do not have a clear subordination to each other.

The central nervous system of man is represented by a bundle of the brain and spinal cord. In the latter distinguish cervical, thoracic, lumbar and sacrococcygeal divisions. They are located in the corresponding parts of the body. Almost all peripheral nervous impulses are carried out to the spinal cord.

The brain is also divided into several parts, each of which has a specific function, but the work of the neocortex, or the cortex of the cerebral hemispheres, is coordinated. So, anatomically distinguish:

• Brain stem;
• medulla;
• Posterior brain (bridge and cerebellum);
• The middle brain (plate of the quadruple and the legs of the brain);
• Forebrain (large hemispheres).

More about each of these parts will be described below. This structure of the nervous system was formed in the process of human evolution so that it could ensure its existence in the new conditions of life.

Spinal cord

This is one of the two organs of the central nervous system. The physiology of his work does not differ from that in the brain: with the aid of complex chemical compounds (neurotransmitters) and the laws of physics (in particular, electricity), information from the small branches of the nerves is combined into large trunks and either realized as reflexes in the corresponding part of the spinal cord, Or enters the brain for further processing.

The spinal cord is in the hole between the arms and the vertebral bodies. It is protected, like the head one, by three shells: hard, arachnoid and soft. The space between these tissue sheets is filled with a liquid that nourishes the nerve tissue, and also performs the function of the shock absorber (mutes vibrations during movements). The spinal cord begins from the opening in the occipital bone, on the border with the medulla oblongata, and ends at the level of the first-second lumbar vertebra. Further, only the shells, cerebrospinal fluid and long nerve fibers ("ponytail") are located. Conditionally anatomists divide it into divisions and segments.

On the sides of each segment (corresponding to the height of the vertebra), sensitive and motor nerve fibers, called roots, depart. These are long processes of neurons whose bodies are directly in the spinal cord. They are a collector of information from other parts of the body.

Medulla

The activity of the nervous system (central) is also involved in the medulla oblongata. He is a part of such an education as the brain stem, and directly in contact with the dorsal. There is a conditional border between these anatomical formations - this is a crossroad of pyramidal pathways. From the bridge it separates the transverse furrow and the area of the auditory canals, which pass in a diamond-shaped fossa.

In the thickness of the medulla oblongata nuclei of the 9th, 10th, 11th and 12th cranial nerves are located, the fibers of the ascending and descending nervous pathways and the reticular formation. This site is responsible for performing protective reflexes, such as sneezing, coughing, vomiting and others. And also supports life in us by regulating breathing and palpitation. In addition, the medulla oblongata contains centers for regulating muscle tone and maintaining the posture.

Bridge

Together with the cerebellum is the back of the central nervous system. What is this? The accumulation of neurons and their processes, located between the transverse groove and the exit point of the fourth pair of cranial nerves. It is a roll-like thickening with a depression in the center (there are vessels in it). The fibers of the trigeminal nerve emerge from the middle of the bridge. In addition, the upper and middle legs of the cerebellum extend from the bridge, while the upper part of the Varoliev bridge hosts the nuclei of the 8th, 7th, 6th and 5th pairs of cranial nerves, the area of the auditory canal and the reticular formation.

The main function of the bridge is the transfer of information to the higher and lower parts of the central nervous system. Through it there are many ascending and descending ways that end or begin their journey in different parts of the cortex of the cerebral hemispheres.

Cerebellum

This is the department of the central nervous system (CNS), which is responsible for coordinating movements, maintaining balance and maintaining muscle tone. It is located between the bridge and the middle brain. To obtain information about the environment, there are three pairs of legs in which nerve fibers pass.

The cerebellum is an intermediate collector of all information. It receives signals from sensitive fibers of the spinal cord, as well as from motor fibers starting in the cortex. After analyzing the obtained data, the cerebellum sends impulses to the motor centers and corrects the position of the body in space. All this happens so quickly and smoothly that we do not notice his work. All of our dynamic automatisms (dancing, playing musical instruments, writing) are the responsibility of the cerebellum.

Middle Brain

In the human CNS there is a department that is responsible for visual perception. They are the middle brain. It consists of two parts:

• The lower one represents the legs of the brain in which the pyramidal pathways pass.
• The upper one is the plate of the quadruple, on which, in fact, the visual and auditory centers are located.

The formations in the upper part are closely connected with the intermediate brain, so there is not even an anatomical border between them. Conditionally, it can be assumed that this is a posterior spike of the cerebral hemispheres. In the middle of the middle brain there are the nuclei of the third cranial nerve - the oculomotor, and in addition the red core (it is responsible for controlling the movements), the black substance (initiates movements) and the reticular formation.

The main functions of this area of the central nervous system:

• Orienting reflexes (reaction to strong stimuli: light, sound, pain, etc.);
• vision;
• The pupil's reaction to light and accommodation;
• Friendly turn of the head and eyes;
• Maintaining the tone of skeletal muscles.

Intermediate brain

This formation is located above the midbrain, immediately under the corpus callosum. It consists of the thalamic part, the hypothalamus and the third ventricle. The thalamic part includes the actual thalamus (or visual hillock), epithalamus, and metatagamus.

• The thalamus is the center of all kinds of sensitivity, it collects all the afferent impulses and redistributes it into the appropriate motor ways.
• Epithalamus (epiphysis, or pineal body) is the endocrine gland. Its main function is the regulation of human biorhythms.
• The metatalamus is formed by medial and lateral geniculate bodies. The medial bodies are the subcortical center of hearing, and the lateral - the view.

The hypothalamus is administered by the pituitary gland and other endocrine glands. In addition, it regulates, in part, the autonomic nervous system. For the speed of metabolism and the maintenance of body temperature, we should thank him exactly. The third ventricle is a narrow cavity in which there is a fluid necessary for feeding the central nervous system.

Cortex of the hemispheres

CNS neocortex - what is it? This is the youngest department of the nervous system, phylo - and ontogenetically it is formed one of the last and represents a series of cells, densely layered on each other. This site occupies about half of the entire space of the cerebral hemispheres. In it are gyruses and furrows.

There are five parts of the cortex: frontal, parietal, temporal, occipital and islet. Each of them is responsible for his work site. For example, in the frontal lobe there are centers of movement and emotions. In the parietal and temporal - the centers of writing, speech, small and complex movements, in the occipital - visual and auditory, and the islet proportion corresponds to equilibrium and coordination.

All information that is perceived by the endings of the peripheral nervous system, whether it's smell, taste, temperature, pressure or something else, gets into the cerebral cortex and is carefully processed. This process is so automated that when a patient stops or becomes upset because of pathological changes, a person becomes disabled.

Functions of the central nervous system

For such a complex formation as the central nervous system, the functions corresponding to it are also characteristic. The first of these is integrative-coordination. It implies the harmonious work of various organs and systems of the body in order to maintain the constancy of the internal environment. The next function is the connection between a person and his environment, adequate responses of the body to physical, chemical or biological stimuli. In addition, this includes social activities.

The functions of the central nervous system cover both metabolic processes, their speed, quality and quantity. For this, there are separate structures, such as the hypothalamus and pituitary gland. Higher mental activity is also possible only through the central nervous system. With the death of the cortex, so-called "social death" is observed, when the human body still remains viable, but as a member of society it no longer exists (can not speak, read, write and perceive other information, and reproduce it).

It is difficult to imagine a person and other animals without the central nervous system. Its physiology is complex and has not been fully understood. Scientists are trying to understand how the most complex biological computer that ever existed existed. But this is similar to how "a bunch of atoms is studying other atoms," so progress in this area is not sufficient.