The article reveals questions about the concept of the sympathetic nervous system, its structure, formation and functions.
Its connection with other parts of the central system is considered, a comparative characteristic of the action of the sympathetic and parasympathetic on the human body is proposed.
General information
The sympathetic nervous system is one of the divisions autonomic nervous systemwith a segmental structure. The main role of the vegetative department is to control unconscious actions.
The main function of the sympathetic nervous system is to ensure the response of the body while its internal state remains unchanged.
Distinguish between the central and peripheral parts of the sympathetic nervous system. The first serves as the main component of the spinal cord, the second is a large number of closely spaced nerve cells.
The center of the sympathetic nervous system is localized to the side of the thoracic and lumbar regions. It processes oxidation, respiration and cardiac activity, thereby preparing the body for intensive work. Therefore, the main time of activity of this nervous system falls on the daytime.
Structure
The central section of the sympathetic system is located to the left and right of the spine. This is where it starts nerve cellsresponsible for the work of internal organs, most glands, organs of vision. In addition, there are centers responsible for sweating and vasomotor processes. It has been clinically proven that the spinal cord is also involved in metabolic processes and the regulation of the body's temperature regime.
Peripheral department consists of two sympathetic trunks located along the entire spinal column. Each trunk contains nerve nodes that together form more complex nerve fibers. Each sympathetic trunk is represented by four sections.
The cervical region is found behind the carotid arteries in the depths of the neck muscles, consists of three nodes - upper, middle and lower. The upper cervical node with a diameter of 1.8 cm is located between the second and third cervical vertebrae. The middle node is located between the thyroid and carotid arteries, sometimes it is not found. The lower cervical node is located at the beginning of the vertebral artery, connecting with the first or second thoracic nodes, forms a common cervicothoracic element. Nerve fibers responsible for cardiac activity and brain function begin from the cervical sympathetic nodes.
The thoracic region is located along the heads of the ribs on both sides of the spine, and is protected by a special opaque dense film. This section is represented by connecting branches and nine nodes of various geometries. Thanks to the thoracic section of the sympathetic trunk, the nerves of the abdominal organs, as well as the vessels of the chest and abdomen, are supplied.
The lumbar (abdominal) section of the sympathetic trunk includes four nodes located in front of the lateral surface of the vertebrae. In the abdominal region, the upper visceral nerve cells are distinguished, which form the celiac plexus, and the lower ones form the mesenteric plexus. With the help of the lumbar spine, the pancreas and intestines are innervated.
The sacral (pelvic) region is represented by four nodes that are located in front of the coccygeal vertebrae. The pelvic nodes give rise to fibers that form the hypogastric plexus, which consists of several segments. The sacral region innervates the urinary organs, rectum, male and female sex glands.
Functions
Takes part in cardiac activity, regulates the frequency, rhythm and strength of heart beats. Increases the clearance in the respiratory organs - lungs and bronchi. Reduces the motor, secretory and absorption capacity of the digestive system. Supports the body in an active state with the constancy of its internal environment. Provides the breakdown of glycogen in the liver. Accelerates the work of the endocrine glands.
Regulates the processes of metabolism and metabolism, which facilitates adaptation to new environmental conditions. Due to the produced adrenaline and norepinephrine, it helps a person to make decisions quickly in difficult situations. Provides innervation to all internal organs and tissues. Participates in strengthening the immune mechanisms of the body, is a stimulant of hormonal reactions.
Reduces the tone of smooth muscle fibers. Increases blood sugar and cholesterol levels. Helps the body get rid of fatty acids and toxic substances. Increases blood pressure indicators. Participates in the delivery of oxygen to the blood arteries and vessels.
Provides the flow of nerve impulses throughout the entire spinal column. Participates in the process of dilating the eye pupils. It brings all centers of sensitivity into a state of excitement. It releases stress hormones - adrenaline and norepinephrine - into the blood vessels. Increases perspiration during exercise. Slows down the formation of saliva.
How is formed
Laying begins in the ectoderm. The main inclusions are formed in the spine, hypothalamus, brain stem. Peripheral inclusions originate in the lateral vertebrae of the spinal cord. From this moment, connecting branches are formed, suitable for the nodes of the sympathetic system. From the third week of embryo growth from neuroblasts, neural trunks and nodes are laid, serving as a prerequisite for the subsequent formation of internal organs. Initially, the trunks are formed in the intestinal walls, then in the heart tube.
The trunks of the sympathetic system consist of the following nodes - 3 cervical, 12 thoracic, 5 abdominal and 4 pelvic. Plexuses of the heart and carotid artery are formed from the cells of the cervical node. The thoracic nodes start the work of the lungs, blood vessels, bronchi, pancreas, lumbar - they are involved in the transmission of nervous reactions to the bladder, male and female genital organs.
The entire process of formation of the sympathetic system takes about four to five months of embryonic growth and fetal development.
Interaction with other parts of the central nervous system
Together with the parasympathetic, it controls the internal activity of the body.
The sympathetic and parasympathetic systems are closely interrelated and work in combination, providing a connection between human organs and the central nervous system.
How these two systems act on the human body is shown in the table:
| Name of the body, system | Sympathetic | Parasympathetic |
|---|---|---|
| eye pupil | extension | constriction |
| salivary glands | small amount, dense structure | copious separation of a watery structure |
| lacrimal glands | no influence | increases |
| sweat glands | increases sweating | does not affect |
| heart | accelerates the rhythm, intensifies contractions | slows down the rhythm, reduces contractions |
| blood vessels | constriction | little effect |
| respiratory system | increases breathing rate, the lumen expands | slows down breathing, the lumen becomes smaller |
| adrenal glands | adrenaline is synthesized | not produced |
| digestive organs | inhibition of activity | increases the tone of the gastrointestinal tract |
| bladder | relaxation | reduction |
| genitals | ejaculation | erection |
| sphincters | activity | braking |
Disturbances in the work of one of the systems can lead to diseases of the respiratory system, musculoskeletal system, heart and blood vessels.
If the sympathetic system predominates, then the following signs of excitability are observed:
- frequent increase in body temperature;
- tingling or numbness in the limbs;
- cardiopalmus;
- increased hunger;
- restless sleep;
- apathy for oneself and the life of loved ones;
- severe headaches;
- increased irritability and sensitivity;
- inattention and distraction.
In the case of increased work of the parasympathetic department, the following symptoms are found:
- the skin is pale and cold;
- the frequency and rhythm of heart contractions decreases;
- fainting conditions are possible;
- increased fatigue;
- indecision;
- frequent depressive conditions.
