n. (context neuroanatomy English) In humans and other vertebrates, the part of the nervous system that regulates the involuntary activity of the heart, intestines and glands. These activities include digestion, respiration, perspiration, metabolism, and the modulation of blood pressure.
n. the part of the nervous system of vertebrates that controls involuntary actions of the smooth muscles and heart and glands [syn: ANS]
The autonomic nervous system (ANS) is a division of the peripheral nervous system that influences the function of internal organs. The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions such as the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal. This system is the primary mechanism in control of the fight-or-flight response and the freeze-and-dissociate response.
Within the brain, the autonomic nervous system is regulated by the hypothalamus. Autonomic functions include control of respiration, cardiac regulation (the cardiac control center), vasomotor activity (the vasomotor center), and certain reflex actions such as coughing, sneezing, swallowing and vomiting. Those are then subdivided into other areas and are also linked to ANS subsystems and nervous systems external to the brain. The hypothalamus, just above the brain stem, acts as an integrator for autonomic functions, receiving ANS regulatory input from the limbic system to do so.
The autonomic nervous system has two branches: the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system is often considered the " fight or flight" system, while the parasympathetic nervous system is often considered the "rest and digest" or "feed and breed" system. In many cases, both of these systems have "opposite" actions where one system activates a physiological response and the other inhibits it. An older simplification of the sympathetic and parasympathetic nervous systems as "excitory" and "inhibitory" was overturned due to the many exceptions found. A more modern characterization is that the sympathetic nervous system is a "quick response mobilizing system" and the parasympathetic is a "more slowly activated dampening system", but even this has exceptions, such as in sexual arousal and orgasm, wherein both play a role.
There are inhibitory and excitatory synapses between neurons. Relatively recently, a third subsystem of neurons that have been named non-noradrenergic, non-cholinergic transmitters (because they use nitric oxide as a neurotransmitter) have been described and found to be integral in autonomic function, in particular in the gut and the lungs.
Although the ANS is also known as the visceral nervous system, the ANS is only connected with the motor side. Most autonomous functions are involuntary but they can often work in conjunction with the somatic nervous system which provides voluntary control.
Usage examples of "autonomic nervous system".
Her hand, on the upper part of his neck, rubbing lightly with empathic concern, soothed the demented fluctuations within control of his malfunctioning, panic-dominated autonomic nervous system.
He actually, at this late moment, when Freya had already been teleported across to Whale's Mouth, felt his autonomic nervous system secrete its hormones of cringing panic.
Because, higher than the autonomic nervous system, was the frontal lobe's awareness that the moment Freya crossed over, it was decided.
These 'filters' are guided by the autonomic nervous system and commonly thought to be out of conscious control.
Even prolonged sexual performance by males is an example of somatic intervention over the autonomic nervous system.
They are in the place that represents the autonomic nervous system.
He felt the beams crawling along his optic nerves, tracing pathways to the deepest centers of his brain there to take possession of his autonomic nervous system.
In Dean's experiments, participant receivers lay quietly on a cot in a darkened room, while an optical plethysmograph with a small light bulb and a photocell recorded changes in their fingers' blood volume, which is a measure of autonomic nervous system activity.
Herbert Benson of Harvard University, author of The Relaxation Response, has shown clearly that even simple relaxation procedures may have profound changes on the autonomic nervous system with such effects as the reduction of high blood pressure.
Galen's physiological explanation for the four temperaments had been wrong, of course, and bile, choler, blood and phlegm had now been replaced as causative agents by the ascending reticular activating system and the autonomic nervous system.