The nervous system is a specific management center of the organism. It is thanks to the proper functioning of the nervous system that we are able to think, feel or perform various activities. The nervous system can be divided into various ways: into the central and peripheral nervous systems, or the somatic and autonomic nervous systems. The structure of the nervous system is as complex as its functions. What is part of the nervous system, what are its functions and what are the diseases of the nervous system?

The nervous systemis considered to be the most important of the systems existing in the human body. This treatment of this part of the body is due to the fact that it is the nervous system that controls the activity of other body systems. The complexity of the structure of the nervous system is certainly not surprising - the structure has so many functions that its complicated organization is generally understandable.

Nervous system: development

The nervous system begins to develop early - its first seeds appear in the body around the third week of prenatal life (about 18-19 days after conception).

The first structure of the nervous system - the nerve plate - is formed from the neuroectoderm (the cells of one of the three leaves of the embryo - the ectoderm, differentiate into it).

The next stage in the development of the human nervous system is the formation of the nerve gland, and when - about 20-25 days after fertilization - its edges become overgrown, the neural tube is formed.
In the second month of fetal life, the nervous system the fetus undergoes successive changes. Brain vesicles form from the neural tube, initiating the development of the three main parts of the brain - they are:

  • forebrain
  • midbrain
  • hindbrain

At the same time, the structures of the ventricular system of the brain are formed.

The next month of the fetus's life is the time when blood vessels supplying the CNS tissues are intensively formed.

The fourth month after fertilization is the time when the process of gyrification within the brain begins, involving the formation of furrows and bends within the brain.
The most important processes related to the development of the nervous system take place during intrauterine life , however, it does not mean that when a man comes into the world, his nervous system is fully developed.

Processes such as myelination (i.e. the formation of myelin sheaths around nerve fibers) begin in the womb, but continue for many long years after birth. It turns out that the processes of myelination can take place up to the age of 20, and sometimes even longer.

Nervous system: morphological division

The basic division of the nervous system distinguishes two parts: the central nervous system and the peripheral nervous system. The central nervous system (CNS) is the most important structure of the human nervous system. It is here that all important centers responsible for controlling various activities of the body are located. The structures of the CNS include:

  • the brain located in the skull (the elements of which include the proper brain, dumbrain and the brainstem, which includes the midbrain, bridge and medulla)
  • spinal cord protected by the structures of the spine

CNS tissues consist of two components. They are gray matter (composed mainly of the bodies of nerve cells) and white matter (composed of the fibers of the cells of the nervous system).
The central nervous system is indeed the center of command of the body's activities, but this structure could not play its role without the peripheral nervous system - it is this second part of the nervous system that is responsible for delivering to the CNS nerve impulses flowing from all structures of the body. The peripheral nervous system includes:

  • cranial nerves (of which there are 12 pairs)
  • spinal nerves (of which there are 31 pairs)
  • nerve ganglia (clusters of nerve cells located in different places in the body)
  • peripheral nerve endings

Nervous system: functional division

The human nervous system can be divided not only by its structure, but also by its functions. In the functional division, the somatic nervous system and the autonomic nervous system are distinguished.

The somatic nervous systemis the part of the nervous system that is primarily related to the activities we become aware of. This element of the nervous system is responsible, inter alia, for movement - these phenomena are controlled by

  • pyramid system- is primarily involved in the performance of intentional and planned activities
  • extrapyramidal system- its function is to control automatic movements, the performance of which we are usually not even aware of)

Layoutnervous somaticalso receives various sensory stimuli, such as touch or temperature, it is also a structure that receives impulses from the sensory organs, i.e. visual, auditory, olfactory or taste stimuli.

The second functional element of the nervous system is theautonomic (vegetative) nervous system . The name of this element of the nervous system comes from the fact that its activity takes place completely without our conscious control. Within the autonomic system there are two opposing parts:

  • sympathetic nervous system
  • parasympathetic system

The autonomic system is responsible for a number of different phenomena, incl. it affects the heart function, regulates the digestive system, controls the condition of the sphincters (including the bladder sphincter), and is responsible for the condition of the pupil (it is the autonomic system that causes the narrowing or dilatation of the pupil) and affects the condition of the respiratory tract ( this system can lead to a narrowing or dilation of the bronchial tubes.)

Nervous system: cell structure

The basic cells that build the nervous system areneurons . There are several elements essential for the functioning of the nervous system. The body of the nerve cell has two types of projections: shorter dendrites and longer axons.

Dendritesare primarily used to transmit information between closely spaced nerve cells.Axonsare, in turn, much longer projections (in humans the length of the axon can reach even about one hundred centimeters) and their function is to send nerve impulses at much longer distances.

The human nervous system may contain up to 15 billion neurons, definitely - because even ten times as many other cells, called glial cells, can be in it. This type of cells of the nervous system include:

  • microglia
  • oligodendrocytes
  • astrocytes
  • ependemocytes
  • Schwann cells

Each of these types of glial cells plays an important role in the nervous system. The cells involved in the formation of myelin sheaths are oligodendrocytes and Schwann cells.

Astrocytes support neurons and influence the transmission of nerve impulses, while ependemocytes are important for the proper function of the blood-brain barrier.

Microglia cells, on the other hand, have the task of defending the structures of the nervous system - the term microglia arenervous system cells of the immune system.

Nervous system: functions

The primary function of the nervous system is to transmit signals - nerve impulses - between nerve cells. This is due to the existence of synapses, i.e. connections between individual neurons, but also between nerve cells and, for example, muscle cells or cells belonging to the sense organs.

The impulses within the nerve cells are sent because these structures are electrically excitable. In this way, the signal travels within the nerve cell until it reaches the synapse, or more specifically its element called the presynaptic terminal. Under the influence of numerous changes, molecules called neurotransmitters are released into the synaptic space. They reach the next element of the synapse - the postsynaptic terminal - and after they bind to the receptors, another electrical impulse is generated.

There are many different neurotransmitters in the human nervous system, the most important of which are:

  • noradrenalina
  • serotonin
  • dopamine
  • glutamic acid
  • gamma-aminobutyric acid (GABA)
  • acetylcholine
  • histamine
  • adrenalina

Thanks to the existence of synapses, the human nervous system can receive information from the external environment - impulses of this kind reach the structures of the CNS thanks to the so-called afferent fibers.

The human body can react differently to the received stimuli - for example, after the information about the low temperature of the environment is registered, the phenomena related to the production of heat in the body can be stimulated. Such information is transferred from the structures of the CNS to the executive organs via other than the aforementioned fibers, i.e. centrifugal (efferent) fibers.

The function of the nervous system is the aforementioned perception of sensory stimuli, but its role is also to control motor activities. It is the structures of the nervous system that control how we walk, write, or reach for any object. It may seem almost unimaginable, but before any activity is performed in the structures of the nervous system, a large number of nerve signals are transmitted, the purpose of which is to ensure the continuity and correctness of a given movement.

The nervous system is the overarching level that controls the activity of other body systems. Centers located in the brain stem influence the activity of the heart, control the activity of the respiratory system or evenregulate blood pressure.

The endocrine system is also in constant connection with the nervous system - organs belonging to the latter, such as the pituitary and hypothalamus, secrete a variety of hormones (such as hypothalamic liberins and statins, and pituitary tropic hormones) that control function and secretion of other endocrine glands, such as the thyroid gland, adrenal glands or gonads.

The functions of the nervous system also include controlling drive behavior. It is in this part of the human body that the centers related to hunger and satiety are located, in addition, the nervous system is also responsible for controlling phenomena related to human sexuality and reproduction.

Within the nervous system, the final processing of stimuli from the sensory organs takes place as well. In the topmost floor of the nervous system - within the CNS - the analysis and integration of impulses received by the sensory organs takes place.

The ear, eye or receptor cells on the tongue and inside the nose are of course necessary for receiving sensory stimuli, but only their appropriate analysis in specific centers of the brain - for example in the visual or auditory cortex - makes us see what we see do we hear what we hear.

Among the functions of the nervous system, it is impossible not to mention the phenomena experienced by every human being, and at the same time still insufficiently known and understood. We are talking about such phenomena as memory or thinking - such phenomena are also possible thanks to the proper functioning of the nervous system.

Nervous system: diseases

Diseases related to the nervous system are de alt with by a neurologist.

There are many different entities in the group of diseases that attack the body's management center. The diseases of the nervous system include:

  • Congenital entities (such as spina bifida, meningeal hernia, hydrocephalus, and anencephaly)
  • infectious disease (such as central nervous system syphilis, meningitis, encephalitis or brain abscess)
  • CNS tumors (there are many different CNS tumors, examples include glioblastoma, meningioma or astrocytoma)
  • in addition, in the CNS there may also be metastases of neoplasms from other organs of the body, as is the case with, for example, lung cancer or melanoma
  • vascular diseases (including e.g. stroke, but also cerebral aneurysms or malformationsCNS vessels)
  • many different types of epilepsy
  • neurodegenerative diseases (such as Alzheimer's disease or Amyotrophic Lateral Sclerosis)
  • multiple sclerosis
  • dementia (e.g. dementia with Lewy bodies or frontotemporal dementia)
  • myasthenia gravis
  • Guillain-Barre syndrome
  • injuries and related - often, unfortunately, irreversible - damage to the nervous system (related, for example, to various hematomas, such as subarachnoid or intracerebral hematoma, or to other problems such as brain contusion or spinal cord rupture)
  • Parkinson's disease
  • prion diseases (e.g. Creutzfeldt-Jakob disease)
  • toxic damage to CNS tissues (e.g. in the form of Korsakoff's syndrome)
  • different types of headache (such as e.g. migraine, cluster headache or paroxysmal hemicransmission)
  • polyneuropathies

The above list - despite its complexity - is only a modest outline of possible diseases of the nervous system.

When discussing this issue, it is impossible not to mention the entities whose occurrence is associated with disorders of the nervous system, i.e. mental diseases and disorders. Problems such as

  • schizophrenia
  • bipolar disorder
  • depression
  • autism
  • mental retardation

are also generally regarded as diseases of the nervous system.

About the authorBow. Tomasz NęckiA graduate of medicine at the Medical University of Poznań. An admirer of the Polish sea (most willingly strolling along its shores with headphones in his ears), cats and books. In working with patients, he focuses on always listening to them and spending as much time as they need.

Category:

Neurology