Reticular activating system


Reticular activating system

Infobox Brain
Name = Reticular activating system
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Caption = Deep dissection of brain-stem. Ventral view. (Reticular formation labeled near center.)


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The reticular activating system (or ARAS, for Ascending Reticular Activating System) is the name given to the part of the brain (the reticular formation and its connections) believed to be the center of arousal and motivation in mammals (including humans).

Functions

The activity of this system is crucial for maintaining the state of consciousness. It is situated at the core of the brain stem between the myelencephalon (medulla oblongata) and mesencephalon (midbrain).

It is involved with the circadian rhythm. Damage can lead to permanent coma. It is thought to be the area affected by many psychotropic drugs. General anesthetics work through their effect on the reticular formation.

Fibers from the reticular formation are also vital in controlling respiration, cardiac rhythms, and other essential functions.

Although the functioning of this system is a prerequisite for consciousness to occur, it is generally assumed that this system's role is indirect and it does not, by itself, generate consciousness. Instead, its unique anatomical and physiological characteristics ensure that the thalamocortical system fire in such a way that is compatible with conscious experience. The reticular activating system controls our sexual patterns.

Clinical significance

The reticular activating system (RAS) has received attention from neuroscientists interested in various pathological conditions affecting behaviour, such as Alzheimer's Disease. More recently, results of research on the area has prompted extrapolations from the data into attention-deficit hyperactivity disorder (ADHD). The reticular activating system is believed to cause ADD and ADHD due to the imbalance of norepinephrine in the cells Fact|date=April 2008.

Another way to look at the RAS is to consider why you can sleep at night through all of the normal sounds of your house, but wake up to the sound of the ruffling pajamas of your child as they walk into your bedroom. This is a function of the RAS. It filters out all of the things you know are normal stimuli and activates when something new or different occurs.

External links

* [http://www.stanford.edu/group/hopes/basics/braintut/f_ab24retiacts.gifDiagram] at Stanford University
* [http://hart.camden.rutgers.edu/intro/brain/sld019.htm Diagram] at Rutgers-Camden
* [http://www.deficitdeatencion.org/reticular.htm deficitdeatencion.org]


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Look at other dictionaries:

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