CNS - what is it? The structure of the human nervous system is described as an extensive electrical network. Perhaps this is the most accurate metaphor possible, since a current really runs through thin threads-fibers. 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 by chance, everything is subject to a strict hierarchy. That is why the central and peripheral nervous systems are distinguished.
Departments of the CNS
Let's consider this system in more detail. And yet, the central nervous system - what is it? Medicine provides 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 whole structure is similar to a cluster of nodules that do not have a clear subordination to each other.
The human central nervous system is represented by a bundle of the brain and spinal cord. In the latter, the cervical, thoracic, lumbar and sacrococcygeal regions are distinguished. They are located in the corresponding parts of the body. Almost all peripheral nerve impulses are conducted to the spinal cord.
The brain toodivided into several parts, each of which has a specific function, but coordinates their work with the neocortex, or the cerebral cortex. So, anatomically allocate:
- brain stem;
- medulla oblongata;
- hindbrain (bridge and cerebellum);
- midbrain (lamina of the quadrigemina and legs of the brain);
- forebrain (large hemispheres).
Details on each of these parts will be discussed below. Such a structure of the nervous system was formed in the process of human evolution so that he could ensure his existence in the new conditions of life.
Spinal cord
This is one of the two organs of the CNS. The physiology of its work does not differ from that in the brain: with the help of complex chemical compounds (neurotransmitters) and the laws of physics (in particular, electricity), information from small branches of nerves is combined into large trunks and either implemented in the form of reflexes in the corresponding section of the spinal cord, or enters the brain for further processing.
The spinal cord is located in the hole between the arches and the bodies of the vertebrae. It is protected, like the head, by three shells: hard, arachnoid and soft. The space between these tissue sheets is filled with a fluid that nourishes the nervous tissue, and also acts as a shock absorber (muffles vibrations during movements). The spinal cord starts from the opening in the occipital bone, on the border with the medulla oblongata, and ends at the level of the first or second lumbar vertebra. Then there are only shells,cerebrospinal fluid and long nerve fibers ("ponytail"). Conventionally, anatomists divide it into departments and segments.
On the sides of each segment (corresponding to the height of the vertebrae), sensory and motor nerve fibers called roots depart. These are long processes of neurons whose bodies are located directly in the spinal cord. They are a collector of information from other parts of the body.
Medulla oblongata
The activity of the nervous system (central) is also involved in the medulla oblongata. It is part of such a formation as the brain stem, and is in direct contact with the spinal cord. There is a conditional border between these anatomical formations - this is the intersection of the pyramidal pathways. It is separated from the bridge by a transverse groove and a section of the auditory pathways that pass in the rhomboid fossa.
In the thickness of the medulla oblongata are the nuclei of the 9th, 10th, 11th and 12th cranial nerves, fibers of the ascending and descending nerve pathways and the reticular formation. This area is responsible for the implementation of protective reflexes, such as sneezing, coughing, vomiting and others. It also keeps us alive by regulating our breathing and heartbeat. In addition, the medulla oblongata contains centers for regulating muscle tone and maintaining posture.
Bridge
Together with the cerebellum is the back of the CNS. What is it? An accumulation of neurons and their processes located between the transverse sulcus and the exit point of the fourth pair of cranial nerves. It is a roller-shaped thickening with a depression in the center (there are vessels in it). From the middle of the bridge exit the fibers of the trigeminal nerve. In addition, the upper and middle peduncles of the cerebellum depart from the bridge, and the nuclei of the 8th, 7th, 6th and 5th pairs of cranial nerves, the section of the auditory pathway and the reticular formation are located in the upper part of the Varoliev bridge.
The main function of the bridge is to transmit information to the higher - and lower parts of the central nervous system. Many ascending and descending paths pass through it, which end or begin their journey in different parts of the cerebral cortex.
Cerebellum
This is the part of the CNS (central nervous system) that is responsible for coordinating movements, maintaining balance and maintaining muscle tone. It is located between the pons and the midbrain. To receive information about the environment, it has three pairs of legs in which nerve fibers pass.
The cerebellum acts as an intermediate collector of all information. It receives signals from sensory fibers of the spinal cord, as well as from motor fibers starting in the cortex. After analyzing the received 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 our dynamic automatisms (dancing, playing musical instruments, writing) are the responsibility of the cerebellum.
Midbrain
In the human CNS there is a department that is responsible for visual perception. It is the midbrain. It consists of two parts:
- The lower one is the legs of the brain, in which the pyramidal pathways pass.
- The upper one is the plate of the quadrigemina, on which, in fact, the visual and auditory centers are located.
Formations in the upper part are closely connected with the diencephalon, so there is not even an anatomical boundary between them. It can be conditionally assumed that this is the posterior commissure of the cerebral hemispheres. In the depths of the midbrain are the nuclei of the third cranial nerve - the oculomotor, and besides this, the red nucleus (it is responsible for controlling movements), the black substance (initiates movements) and the reticular formation.
The main functions of this region of the central nervous system:
- orienting reflexes (reaction to strong stimuli: light, sound, pain, etc.);
- vision;
- pupil response to light and accommodation;
- friendly head and eye turn;
- maintaining skeletal muscle tone.
Diencephalon
This formation is located above the midbrain, just below the corpus callosum. It consists of the thalamic part, the hypothalamus and the third ventricle. The thalamic part includes the thalamus proper (or thalamus), the epithalamus, and the metathalamus.
- The thalamus is the center of all types of sensitivity, it collects all afferent impulses and redistributes them to the appropriate motor pathways.
- Epithalamus (pineal gland, or pineal gland) is an endocrine gland. Its main function isregulation of human biorhythms.
- Metalalamus is formed by the medial and lateral geniculate bodies. The medial bodies represent the subcortical center of hearing, and the lateral bodies represent vision.
The hypothalamus controls the pituitary gland and other endocrine glands. In addition, it regulates partly the autonomic nervous system. For the speed of metabolism and maintenance of body temperature, we must thank him. The third ventricle is a narrow cavity that contains the fluid needed to feed the central nervous system.
Cortex of hemispheres
CNS neocortex - what is it? This is the youngest part of the nervous system, phylo - and ontogenetically it is one of the last to be formed and represents rows of cells densely layered on top of each other. This area occupies about half of the entire space of the cerebral hemispheres. It contains convolutions and furrows.
There are five parts of the cortex: frontal, parietal, temporal, occipital and insular. Each of them is responsible for their area of work. For example, in the frontal lobe are the centers of movement and emotions. In the parietal and temporal lobe - the centers of writing, speech, small and complex movements, in the occipital - visual and auditory, and the insular lobe corresponds to balance and coordination.
All information that is perceived by the endings of the peripheral nervous system, whether it be smell, taste, temperature, pressure or anything else, enters the cerebral cortex and is carefully processed. This process is so automated that when, in view of pathological changes, it stops orgets upset, the person becomes disabled.
CNS functions
For such a complex formation as the central nervous system, the functions corresponding to it are also characteristic. The first of them is integrative-coordinating. It implies the coordinated work of various organs and systems of the body to maintain the constancy of the internal environment. The next function is the connection between a person and his environment, adequate reactions of the body to physical, chemical or biological stimuli. It also includes social activities.
Functions of the central nervous system also cover metabolic processes, their speed, quality and quantity. To do this, there are separate structures, such as the hypothalamus and the pituitary gland. Higher mental activity is also possible only thanks to the central nervous system. When the cortex dies, the so-called “social death” is observed, when the human body still retains its vitality, but as a member of society, it no longer exists (cannot speak, read, write and perceive other information, as well as reproduce it).
It is difficult to imagine humans and other animals without the central nervous system. Its physiology is complex and not yet fully understood. Scientists are trying to figure out how the most complex biological computer ever worked. But it's like "a bunch of atoms learning other atoms", so advances in this area are not enough yet.
