Wakefulness is a daily recurringbrain state and state ofconsciousness in which an individual is conscious and engages in coherentcognitive and behavioral responses to the external world.
Being awake is the opposite of beingasleep, in which most external inputs to the brain are excluded from neural processing.[1][2][3][4]
The longer the brain has been awake, the greater the synchronous firing rates ofcerebral cortex neurons. After sustained periods of sleep, both the speed and synchronicity of the neurons firing are shown to decrease.[5]
Another effect of wakefulness is the reduction ofglycogen held in theastrocytes, which supply energy to the neurons. Studies have shown that one of sleep's underlying functions is to replenish this glycogen energy source.[6]
Wakefulness is produced by a complex interaction between multiple neurotransmitter systems arising in thebrainstem and ascending through themidbrain,hypothalamus,thalamus andbasal forebrain.[7] The posterior hypothalamus plays a key role in the maintenance of the cortical activation that underlies wakefulness. Several systems originating in this part of the brain control the shift from wakefulness into sleep and sleep into wakefulness.Histamine neurons in thetuberomammillary nucleus and nearby adjacent posterior hypothalamus project to the entire brain and are the most wake-selective system so far identified in the brain.[8] Another key system is that provided by theorexins (also known as hypocretins) projecting neurons. These exist in areas adjacent to histamine neurons and like them project widely to most brain areas and associate witharousal.[9] Orexin deficiency has been identified as responsible fornarcolepsy.[10]
Research suggests that orexin and histamine neurons play distinct, but complementary roles in controlling wakefulness with orexin being more involved with wakeful behavior and histamine with cognition and activation of corticalEEG.[11]
It has been suggested thefetus is not awake, with wakefulness occurring in thenewborn due to the stress of beingborn and the associated activation of thelocus coeruleus.[12]
^Sakurai, T (2007). "The neural circuit of orexin (hypocretin): maintaining sleep and wakefulness".Nature Reviews. Neuroscience.8 (3):171–81.doi:10.1038/nrn2092.PMID17299454.S2CID8932862.
Category
The dictionary definition ofwakefulness at Wiktionary