The human body is composed of a plurality of cells combined in individual tissues and organs having interconnected multiple links. Dynamic equilibrium in the body or constant internal environment called homeostasis Homeostasis: physiological mechanisms . Homeostasis is provided by separate systems, are responsible for certain functions. One such system is the autonomic nervous system that is responsible for vegetative homeostasis.

The autonomic nervous system and vegetative homeostasis

The autonomic nervous system (ANS) - a division of the nervous system, responsible for the work of the internal organs, glands, blood and lymph vessels. ANS adjusts the function of internal organs to changes in the external environment, providing vegetative homeostasis. VNS has an impact not only on the physical but also in human mental activity.

ANS controls the cardiovascular system, respiratory system, digestion, excretion, reproductive system, metabolism and growth of the organism. VNS is not subject to control only the activity of skeletal muscle.

VNS is divided into the sympathetic (SNS) and the parasympathetic (PNS) whose influence on organs and systems are sometimes diametrically opposed. The balance between the SNS and PNS, and determines the state of vegetative homeostasis.

Sympathicus

SNA - is part of the SNC, which ganglia (ganglia) located at a considerable distance from the innervated organs. SNA is divided into the center (it is in the thoracic and lumbar spinal cord) and peripheral in the form of interconnected nerve branches, and paravertebral prespinal (removed from the spinal cord) nodes.

The sympathetic nervous system provides the "wards" of under stress when switched signals "hit" or "run". Of course, today such signals person reacts not as primitive, the reaction on the part of the body remains the same: the body is on full alert in order to help a person get out of the situation.

When excited by SNA stand neurotransmitters (substances with which nerve impulses are transmitted), epinephrine and norepinephrine, which have an impact on individual organs and systems. Increased heart rate and arterial blood supply to organs and tissues (blood brings with it extra food and oxygen), the arteries are narrowed (to retain heat and energy needed to overcome obstacles), increased blood pressure. Bronchi, on the contrary, are expanding, increasing respiratory rate, blood is better oxygenated. Functions of the digestive system, including the activities of the salivary glands and digestive oppressed (that did not take the extra energy), the bladder muscles relax, the pupils dilate (light actively irritating the retina, stimulating vision).

The parasympathetic nervous system

If the stress is dominated by effects on the SNA, the normal activities of SNS balanced by PNS activity that forms a vegetative homeostasis. A neurotransmitter that transmits the excitation of nerve fibers PNS is acetylcholine.

The PNS ganglia are located right in the bodies or next to them. Allocate the central and the peripheral part. Central Division PNS includes nuclei located in the brain (nucleus of cranial nerve) and sacral region of the spinal cord.

PNS different organs have different effects (inhibits or excites their functions). In the cardiovascular system, it has an inhibiting effect: reduces the frequency and strength of contractions of the heart, relaxes the muscles of the walls of the arteries, lowers blood pressure. Inhibits TNC activities and Respiratory narrowed bronchi, respiratory rate and ventilation is reduced. On the contrary, on the digestive organs, it has a stimulating effect: increases motor activity of the intestine, saliva and digestive juices (the body needs nutrient reserves). The walls of the bladder contract, the pupils constrict (Light less irritating to the retina, which creates a state of rest).

Maintenance of vegetative homeostasis

Sympathetic and parasympathetic division of the ANS have different, in some cases the opposite direction of the impact on the various organs and tissues, as well as mutually influence each other. Such different effects SNS and PNS on the same organs and tissues depends on the properties of the emissions of neurotransmitters and receptors features available on the membranes of nerve cells (neurons) VNS and target cells located in specific organs.

Vegetative homeostasis allows the human body to function in conditions of stress, concentrating and wasting energy generously and in normal conditions, ensuring the vital activity of the person and saving energy in reserve.

Galina Romanenko

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