which is reduced during sleep  and increased during wakefulness.   Centrally, arousal is modulated by the reticular activating system of the brain.  Peripherally, arousal is modulated by autonomic inputs and endocrine hormones/neurotransmitters (e.g.  norepinephrine, dopamine). Posted by David Cohen at 9:26 AM Email This BlogThis! Share to Twitter Share to Facebook Labels: CFS circadian