Reticular activating system (RAS (occasionally ARAS for ascending reticular activating system))

The Reticular activating system is a functional network within the brainstem composed of interconnected nuclei, including the locus coeruleus, raphe nuclei, tuberomammillary nucleus, and pedunculopontine tegmentum, which regulate arousal, wakefulness, attention, and filtering of sensory information to the cortex. These nuclei use diverse neurotransmitters (norepinephrine, serotonin, histamine, acetylcholine) to modulate global brain states and help determine what sensory input reaches conscious awareness, contributing to sleep-wake cycles, attention, emotional responses, and learning and habituation. Dysfunction of the system can result in coma, narcolepsy, or attentional deficits. The RAS is not a molecular target or receptor itself, but drugs modulate its function via neurotransmitter pathways within its component nuclei.

Other names

ARAS (Ascending reticular activating system)reticular formation (when referring more broadly)

Alter neurotransmitter release or receptor activation within nuclei of the RAS (e.g. locus coeruleus - norepinephrine, raphe nuclei - serotonin, tuberomammillary nucleus - histamine, pedunculopontine tegmentum - acetylcholine); Modulate sleep-wake transitions and arousal states via effects on RAS circuitry