Wakefulness is a daily recurring
brain state and state of
consciousness in which an individual is conscious and engages in coherent
cognitive
Cognition refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasses all aspects of intellectual functions and processes such as: perception, attention, thought, ...
and behavioral responses to the external world.
Being awake is the opposite of being a
sleep, in which most external inputs to the brain are excluded from neural processing.
Effects upon the brain
The longer the brain has been awake, the greater the synchronous firing rates of
cerebral cortex neurons. After sustained periods of sleep, both the speed and synchronicity of the neurons firing are shown to decrease.
Another effect of wakefulness is the reduction of
glycogen
Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria. The polysaccharide structure represents the main storage form of glucose in the body.
Glycogen functions as one o ...
held in the
astrocytes, which supply energy to the neurons. Studies have shown that one of sleep's underlying functions is to replenish this glycogen energy source.
Maintenance by the brain
Wakefulness is produced by a complex interaction between multiple neurotransmitter systems arising in the
brainstem
The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is cont ...
and ascending through the
midbrain,
hypothalamus,
thalamus and
basal forebrain. 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 the
tuberomammillary nucleus and nearby adjacent posterior hypothalamus project to the entire brain and are the most wake-selective system so far identified in the brain. Another key system is that provided by the
orexins (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 with
arousal
Arousal is the physiological and psychological state of being awoken or of sense organs stimulated to a point of perception. It involves activation of the ascending reticular activating system (ARAS) in the brain, which mediates wakefulness, th ...
. Orexin deficiency has been identified as responsible for
narcolepsy.
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 cortical
EEG.
It has been suggested the
fetus is not awake, with wakefulness occurring in the
newborn due to the stress of being
born
Born may refer to:
* Childbirth
* Born (surname), a surname (see also for a list of people with the name)
* ''Born'' (comics), a comic book limited series
Places
* Born, Belgium, a village in the German-speaking Community of Belgium
* Born, Luxe ...
and the associated activation of the
locus coeruleus
The locus coeruleus () (LC), also spelled locus caeruleus or locus ceruleus, is a nucleus in the pons of the brainstem involved with physiological responses to stress and panic. It is a part of the reticular activating system.
The locus coerule ...
.
See also
*
Dream argument
*
Eugeroic
*
High-conductance state
*
Lucid dream
*
Sleepwalking
References
External links
{{Authority control
Cognition
Mental states