Reticular activating system in the brain

Talks about the RAS in the brain of a human body

1. Reticular activating system

2. RETICULAR ACTIVATING SYSTEM Is an area of the brain (including the reticular formation and its connections) responsible for regulating arousal and sleep-wake transitions. It is one of the most important parts of the brain, which controls many vital brain functions of consciousness. Moruzzi and magoun first investigated the brain`s sleep-wake mechanisms in 1949. It was later appreciated that the RAS is responsible for many cognitive functions related to awareness.

3. Anatomical components The RAS is composed of several neuronal circuits connecting the brainstem to the cortex. This pathway originates in the upper brainstem reticular core and project through synaptic relays in the rostral intralaminar and thalamic nuclei to the cerebral cortex. Several areas traditionally included in the RAS are; Midbrain reticular formation Mesencephalic nucleus (mesencephalon) Thalamic intralaminar nucleus Dorsal hypothalamus tegmentum

4. Neurotransmitters The neuronal circuits of the RAS are modulated by complex interactions between a few main neurotransmitter. The RAS contains both cholinergic and adrenergic components , which exhibits synergy as well as competitive actions to regulate thalamocortical activity and the corresponding behavioral state The RAS functions are controlled by certain cholinergic (related to acetylcholine) and adrenergic (related to adrenaline) neurotransmitters.

5. RAS; location and structure The RAS connects the lower parts of the brain, which is the brain stem, to the cerebral cortex through various neural paths . The brain stem controls most of the involuntary functions as well as reflexes of the body , while cerebral cortex is the seat of consciousness and thinking abilities. So, the RAS forms a link between these two different regions. It is a bridge between the upper brain and the lower brain.

6. RAS; Location & structure One is the ascending RAS (which has connections with the cerebral cortex, hypothalamus and thalamus) and the other is the descending RAS (which is connected to the cerebellum and many sensory nerves) A large part of the RAS consists of the brain parts that are responsible for the survival instincts. Hence it has a deep connection with awareness functions of the brain.

7. Function Regulating sleep-wake transitions The main function of the RAS is to modify and potentiate thalamic and cortical functions such that electroencephalogram(EEG) desynchronization ensures. There are distinct differences in the brain`s electrical activity during periods of wakefulness and sleep; Low voltage fast burst brain waves (EEG desynchronization) are associated with wakefulness and REM sleep (which are electro physiologically identical) Large voltage slow waves are found during non-REM sleep. When thalamic relay neurons are in burst mode the EEG is synchronized and when they are in tonic mode it is desynchronized.