CNS - what is it? The structure of the human nervous system is described as a branched electric network. Perhaps this is the most accurate metaphor possible, since the current runs through thin filaments of 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 system is isolated .
CNS departments
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 chordate animals 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 a person is represented by a bundle of the brain and spinal cord. In the latter, the cervical, thoracic, lumbar and sacrococcygeal are distinguished. They are located in the corresponding parts of the body. Almost the entire peripheral nerve impulse is carried out to the spinal cord.
The brain is also divided into several parts, each of which has a specific function, but the neocortex, or cerebral cortex, coordinates their work. So, anatomically distinguish:
- brain stem;
- medulla;
- hindbrain (bridge and cerebellum);
- midbrain (quadruple plate and brain legs);
- forebrain (cerebral hemispheres).
Details on each of these parts will be described below. This structure of the nervous system was formed in the process of human evolution so that he could ensure his existence in new conditions of life.
Spinal cord
This is one of two organs of the central nervous system. The physiology of his 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 is either realized as 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 vertebral bodies. It is protected, like the head, by three shells: hard, arachnoid and soft. The space between these tissue sheets is filled with fluid that nourishes the nerve tissue, and also acts as a shock absorber (dampens vibrations during movements). The spinal cord begins from an opening in the occipital bone, at the border with the medulla oblongata, and ends at the level of the first or second lumbar vertebra. Further 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 vertebra), sensitive and motor nerve fibers, called roots, extend. 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
The activity of the nervous system (central) is also involved in the medulla oblongata. It is part of such an entity 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 paths. From the bridge it is separated by a transverse groove and a section of the auditory tract, which pass in a 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 paths and the reticular formation. This area is responsible for performing protective reflexes, such as sneezing, coughing, vomiting, and others. It also supports life in us by regulating respiration and heartbeat. In addition, the medulla oblongata contain centers for regulating muscle tone and maintaining posture.
Bridge
Together with the cerebellum is the back of the central nervous system. What is this? A cluster of neurons and their processes located between the transverse groove and the exit site of the fourth pair of cranial nerves. It is a roll-shaped thickening with a depression in the center (there are vessels in it). From the middle of the bridge go the trigeminal fibers. In addition, the upper and middle legs of the cerebellum extend from the bridge, and the nuclei of the 8th, 7th, 6th and 5th pairs of cranial nerves, the part 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 path in different parts of the cerebral cortex.
Cerebellum
This is a section of the central nervous system (central nervous system), which is responsible for coordinating movements, maintaining balance and maintaining muscle tone. It is located between the bridge and the midbrain. To obtain 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 the sensitive fibers of the spinal cord, as well as from motor fibers starting in the cortex. After analyzing the data, the cerebellum sends impulses to the motor centers and adjusts the position of the body in space. All this happens so quickly and harmoniously that we do not notice its work. All our dynamic automatisms (dancing, playing musical instruments, writing) are the duty of the cerebellum.
Midbrain
In the human central nervous system 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 paths pass.
- The upper one is a quadruple plate on which, in fact, the visual and auditory centers are located.
The formations in the upper part are closely connected with the diencephalon, so there is not even an anatomical border between them. Conditionally, we can assume 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 in addition there is also the red nucleus (it is responsible for controlling movements), the black substance (initiates movements) and the reticular formation.
The main functions of this area of the central nervous system:
- indicative reflexes (reaction to strong stimuli: light, sound, pain, etc.);
- vision;
- pupil reaction to light and accommodation;
- friendly rotation of the head and eyes;
- maintaining skeletal muscle tone.
Diencephalon
This formation is located above the midbrain, immediately below the corpus callosum. It consists of the thalamic part, the hypothalamus and the third ventricle. The thalamic part includes the thalamus itself (or visual tubercle), epithalamus and metatalamus.
- The thalamus is the center of all types of sensitivity, it collects all the afferent impulsation and redistributes it into the corresponding motor paths.
- The epithalamus (pineal gland, or pineal gland) is the endocrine gland. Its main function is the regulation of human biorhythms.
- The metalamus is formed by medial and lateral cranked bodies. Medial bodies represent the subcortical center of hearing, and lateral bodies represent vision.
The hypothalamus is administered by the pituitary gland and other endocrine glands. In addition, it partly regulates the autonomic nervous system. For the speed of metabolism and maintaining body temperature, we must thank him. The third ventricle is a narrow cavity in which is the fluid needed to supply the central nervous system.
Hemisphere cortex
Neocortex CNS - what is it? This is the youngest part of the nervous system, the filo - and ontogenetically it is formed by one of the latter and is a series of cells densely layered on each other. This site occupies about half of the entire space of the cerebral hemispheres. There are gyrus and furrows in it.
Five parts of the cortex are distinguished: frontal, parietal, temporal, occipital and islet. Each of them is responsible for its own area of work. For example, in the frontal lobe there are centers of movements and emotions. In the parietal and temporal - 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 is smell, taste, temperature, pressure, or anything else, gets into the cerebral cortex and is carefully processed. This process is so automated that when, due to pathological changes, it stops or becomes frustrated, a person becomes disabled.
CNS functions
For such a complex formation as the central nervous system, its corresponding functions are also characteristic. The first of these is integrative coordination. It implies the coordinated work of various organs and systems of the body to maintain a constant 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. In addition, this includes social activities.
The functions of the central nervous system include metabolic processes, their speed, quality and quantity. There are separate structures for this, such as the hypothalamus and 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 remains viable, 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 a central nervous system. Its physiology is complex and has not yet been fully studied. Scientists are trying to understand how the most complex biological computer of all ever existed. But this is similar to how “a bunch of atoms study other atoms,” so advancements in this area are not yet sufficient.