Autonomous Nervous system

The autonomous nervous system or vegetative nervous system or visceral nervous system is the part of the Nervous system responsible for the automatic functions such as the Digestion, the Sudation… the nervous system autonomous or visceral contains peripheral but such central neurons (lower cf).

The maintenance of the balance of the interior medium, or homeostasis, implies complex interactions between physiological and behavioral aspects. Langley has, in 1903, introduces the concept of nervous system autonomous to describe the component of the nervous system in load of this function, opposition to neurons controlling voluntarily or consciously functions such as the movement of a member. Langley described the autonomous nervous system like primarily driving, controlling secreting glands, the cardiac muscles and the smooth muscles of the internal organs and the blood-vessels. It did not integrate into it the related fibers which it regarded as minor and purely somatic (relaying mainly the feelings like the pain).

This old vision of a mainly driving autonomous nervous system still persists. It is known however today that the majority of fibers contained in the vagus, for example, are sensory and relay the visceral feelings implied in homeostasis. This nomenclature moreover was called into question, with the profit of the term of visceral nervous system (Blessing, 1997). This term of visceral nervous system is more suitable because it functionally characterizes the neurons which compose it.

The autonomous nervous system or visceral control indeed functions respiratory, digestive and cardiovascular: it acts on visceral motricity and secretions , the endocrine glands exocrines and and the Vasomotricité. Its driving territory thus included the whole of the smooth muscles. On the sensory level, it processes the data coming from the visceral sensitivity (blood Pression, dilation of the intestines…).

It is composed of related ways (composed by the cranial sensory ganglia) relaying sensory information, like measurements of the blood pressure or the oxygen content of blood. This information converges on the level of an integrating center, the core of the solitary tract, located in the central nervous system. This one sends information in the efferent ways to modify for example the dilation of the bronchi or the release of gastric juices.

The disordered state of the autonomous or visceral nervous system involves a dystonie or neurovégétative dysautonomy.

The efferent part of the autonomous or visceral nervous system is divided into three components: the enteric Nervous system and two systems with the antagonistic functions, the sympathetic Nervous system and the parasympathetic Nervous system.

Structure of the autonomous nervous system

SNA is composed of the systems sympathetic nerve, parasymphatic and enteric. The systems sympathetic nerves and parasympathetics generally exert antagonistic effects on the same target bodies.

the system sympathetic nerve is associated with the mobilization of energy in period of stress. The sympathetic nerve effects are the dilation of pupils and bronchioles, the increase in the respiratory cardiac rhythm and the blood pressure. The symphatic action of the system is permanent but paramount in emergency.

the parasympathetic nervous system (rest and digestion) saves energy and maintains the activities basic on their levels copilots.

See too

Simple: Autonomic nervous system

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