Proper functioning of the nervous system on various fronts is extremely important for a full human life. The human nervous system is considered the most complex structure of the body.
Modern ideas about the functions of the nervous system
The complex communication network, which in biological science is referred to as the nervous system, is divided into central and peripheral, depending on the location of the nerve cells themselves. The first combines cells located inside the brain and spinal cord. But the nerve tissues that are located outside them form the peripheral nervous system (PNS).
The central nervous system (CNS) implements the key functions of processing and transmitting information, interacts with the environment. The nervous system works according to the reflexprinciple. A reflex is an organ's response to a specific stimulus. Nerve cells of the brain are directly involved in this process. Having received information from the neurons of the PNS, they process it and send an impulse to the executive organ. According to this principle, all voluntary and involuntary movements are carried out, the sense organs (cognitive functions) work, thinking and memory work, etc.
Cell Mechanisms
Regardless of the functions of the central and peripheral nervous systems and the location of cells, neurons share some common characteristics with all cells in the body. So, each neuron consists of:
- membrane, or cytoplasmic membrane;
- cytoplasm, or the space between the shell and the nucleus of the cell, which is filled with intracellular fluid;
- mitochondria, which provide the neuron itself with the energy they receive from glucose and oxygen;
- microtubes - thin structures that perform support functions and help the cell maintain its primary shape;
- endoplasmic reticulum - internal networks that the cell uses to sustain itself.
Distinctive features of nerve cells
Nerve cells have specific elements that are responsible for their communication with other neurons.
Axons are the main processes of nerve cells through which information is transmitted along the neural circuit. The more outgoing channels of information transmission a neuron forms, theits axon has more ramifications.
Dendrites are other processes of a neuron. They have input synapses - specific points where contact with neurons occurs. Therefore, the incoming neural signal is called synoptic transmission.
Classification and properties of nerve cells
Nerve cells, or neurons, are divided into many groups and subgroups, depending on their specialization, functionality, and place in the neural network.
The elements responsible for the sensory perception of external stimuli (vision, hearing, tactile sensations, smell, etc.) are called sensory. Neurons that combine in networks to provide motor functions are called motor neurons. Also in the NN there are mixed neurons that perform universal functions.
Depending on the location of the neuron in relation to the brain and the executive organ, cells can be primary, secondary, etc.
Genetically, neurons are responsible for the synthesis of specific molecules with which they build synaptic connections with other tissues, but nerve cells do not have the ability to divide.
This is also the basis for the statement, widespread in the literature, that “nerve cells do not regenerate”. Naturally, neurons incapable of division cannot be restored. But they are able to create many new neural connections every second to perform complex functions.
Thus, the cells are programmed to constantly create more and moreconnections. This is how a complex network of neural communications develops. The creation of new connections in the brain leads to the development of intelligence, thinking. Muscular intelligence also develops in a similar way. The brain is irreversibly improved by learning more and more motor functions.
The development of emotional intelligence, physical and mental, occurs in the nervous system in a similar way. But if the focus is on one thing, other functions are not developing so rapidly.
Brain
The brain of an adult human weighs approximately 1.3-1.5 kg. Scientists have found that up to 22 years of age, its weight gradually increases, and after 75 years it begins to decrease.
There are more than 100 trillion electrical connections in the brain of the average individual, which is several times more than all the connections in all electrical devices in the world.
Researchers spend decades and tens of millions of dollars studying and trying to improve brain function.
Departments of the brain, their functional characteristics
Still, modern knowledge about the brain can be considered sufficient. Especially considering that the ideas of science about the functions of individual parts of the brain made possible the development of neurology, neurosurgery.
The brain is divided into the following zones:
Forebrain. The forebrain regions are usually credited with "higher" mental functions. It includes:
- frontal lobes responsible for coordinating the functions of other areas;
- temporal lobes responsible for hearing and speech;
- The parietal lobes regulate movement control and sensory perceptions.
- occipital lobes responsible for visual functions.
2. The midbrain includes:
- Thalamus, where almost all information entering the forebrain is processed.
- The hypothalamus controls information coming from the organs of the central and peripheral nervous system and the autonomic nervous system.
3. Hind brain includes:
- The medulla oblongata, which is responsible for the regulation of biorhythms and attention.
- The brainstem gives rise to nerve pathways through which the brain communicates with the structures of the spinal cord, it is a kind of communication channel between the central and peripheral nervous system.
- The cerebellum, or small brain, is a tenth of the mass of the brain. Above it are two large hemispheres. The coordination of human movements, the ability to maintain balance in space depends on the work of the cerebellum.
Spinal cord
The average length of an adult spinal cord is approximately 44 cm.
It originates from the brain stem and passes through the foramen magnum in the skull. It ends at the level of the second lumbar vertebra. The end of the spinal cord is called the brain cone. It ends with a cluster of lumbar and sacral nerves.
From dorsalbrain branches 31 pairs of spinal nerves. They help connect the parts of the nervous system: central and peripheral. Through these processes, parts of the body and internal organs receive signals from the NS.
The primary processing of reflex information also takes place in the spinal cord, which accelerates the process of a person's response to stimuli in dangerous situations.
Liquor, or cerebral fluid, common to the spinal cord and brain, is formed in the vascular nodes of the brain fissures from blood plasma.
Normally, its circulation should be continuous. Liquor creates a constant internal cranial pressure, performs shock-absorbing and protective functions. CSF composition analysis is one of the simplest ways to diagnose serious NS diseases.
What causes lesions of the central nervous system of various origins
Nervous system lesions, depending on the period, are divided into:
- Preperinatal - brain damage during fetal development.
- Perinatal - when the lesion occurs during childbirth and in the first hours after birth.
- Postnatal - when damage to the spinal cord or brain occurs after birth.
Depending on the nature, CNS lesions are divided into:
- Traumatic (most obvious). It must be taken into account that the nervous system is of paramount importance for living organisms and from the point of view of evolution, therefore the spinal cord and brain are reliably protected nearby.membranes, pericerebral fluid and bone tissue. However, in some cases this protection is not enough. Some injuries lead to damage to the central and peripheral nervous system. Traumatic lesions of the spinal cord are much more likely to lead to irreversible consequences. Most often, these are paralysis, moreover, degenerative (accompanied by the gradual death of neurons). The higher the damage occurred, the more extensive the paresis (decrease in muscle strength). The most common injuries are open and closed concussions.
- Organic damage to the central nervous system often occurs during childbirth and leads to cerebral palsy. They arise due to oxygen starvation (hypoxia). It is a consequence of prolonged childbirth or entanglement with the umbilical cord. Depending on the period of hypoxia, cerebral palsy can be of different severity: from mild to severe, which is accompanied by a complex atrophy of the functions of the central and peripheral nervous system. CNS lesions after stroke are also defined as organic.
- Genetically determined CNS lesions occur due to mutations in the gene chain. They are considered hereditary. The most common are Down's syndrome, Tourette's syndrome, autism (genetic and metabolic disorder), which appear immediately after birth or in the first year of life. Kensington's, Parkinson's, Alzheimer's diseases are considered degenerative and manifest in middle or old age.
- Encephalopathies - most often occur as a result of damage to brain tissues by pathogens (herpeticencephalopathy, meningococcal, cytomegalovirus).
Structure of the peripheral nervous system
PNS form nerve cells located outside the brain and spinal canal. It consists of nerve nodes (cranial, spinal and autonomic). There are also 31 pairs of nerves and nerve endings in the PNS.
In a functional sense, the PNS consists of somatic neurons that transmit motor impulses and contact with sensory receptors, and autonomic neurons that are responsible for the activity of internal organs. Peripheral neural structures contain motor, sensory and autonomic fibers.
Inflammatory processes
Diseases of the central and peripheral nervous systems are completely different. If CNS damage most often has complex, global consequences, then PNS diseases often manifest themselves in the form of inflammatory processes in the areas of nerve nodes. In medical practice, such inflammation is called neuralgia.
Neuralgia is a painful inflammation in the area of accumulation of nerve nodes, irritation of which causes an acute reflex attack of pain. Neuralgia includes polyneuritis, radiculitis, inflammation of the trigeminal or lumbar nerve, plexitis, etc.
The role of the central and peripheral nervous system in the evolution of the human body
The nervous system is the only one of the systemshuman body that can be improved. The complex structure of the human central and peripheral nervous system is genetically and evolutionarily determined. The brain has a unique property called neuroplasticity. This is the ability of CNS cells to take on the functions of neighboring dead cells, building new neural connections. This explains the medical phenomena when children with organic brain damage develop, learn to walk, speak, etc., and people after a stroke eventually restore the ability to move normally. All this is preceded by the construction of millions of new connections between the central and peripheral parts of the nervous system.
With the progress of various techniques for recovering patients from brain injuries, techniques for developing human potential are also being born. They are based on the logical assumption that if both the central and peripheral nervous systems can recover from injury, then he althy nerve cells can also develop their potential almost indefinitely.
