Module 10: Figure sleep/wake cycle regulation
Regulation of the sleep/wake cycle.
The ascending arousal system consists of neurons distributed in different brain regions such as the orexinergic neurons in the lateral hypothalamus; cholinergic neurons in the basal forebrain (BF), pedunculopontine tegmental (PPT) nucleus and the laterodorsal tegmental (LDT) nucleus; serotonergic neurons in the dorsal raphe (DR); histaminergic neurons in the tuberomammillary nucleus (TMN); noradrenergic neurons in the locus coeruleus (LC); dopaminergic neurons in the substantia nigra pars compacta (Snc) and ventral tegmental atea (VTA). The neurotransmitters released by this arousal system act on neural circuits to regulate the sleep/wake cycle. The orexinergic neurons that release orexin are master regulators in that they also act by stimulating the other arousal neurons. The orexinergic neurons may also integrate the action of a number of other regulators of the sleep/wake cycle. Sleep-inducing systems such as the VPLO neurons have the opposite effect in that they release GABA to inhibit both the orexinergic and the other arousal neurons.