Sleep,
The Ever-Precious Commodity
; Everyone sleeps. Some of us don’t
sleep enough, and some of us sleep too much. But why do we even need it?
Furthermore, what is happening to our brains when we are in this
condition? &
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Sleep is one of several circadian rhythms observed in many different
kinds of species. These types of rhythms follow a daily circuit,
and many are regulated by light. Such circuits are regulated by an
endogenous clock, which was discovered to exist in the suprachiasmatic
nucleus, so called because of its position above the optic chiasm in the
hypothalamus.
When humans sleep, they undergo a cycle of sleeping and waking.
The two kinds of sleeping states are Slow-wave sleep, or SWS sleep, and
Rapid Eye Movement, or REM sleep. The cycles in and out of these
two stages of sleep and waking are controlled by different parts o
f the
brain.
The basal forebrain releases GABA in the hypothalamus to induce and
maintain SWS sleep. General anesthesia actually works by affecting
this neurotransmitter in t
he basal forebrain to activate SWS.
The reticular formation of the brainstem extends from the medulla through
the thalamus, then to other parts of the brain. This image is of
t
he reticular formation in the medulla. It functions as a switch
between SWS and REM sleep. The raphe nucleus is important here, as well, as it
promotes SWS sleep.
A small region
in the pons, just ventral to the locus coeruleus, is
instrumental in inducing REM sleep. The muscle atonia
characteristic of REM sleep is controlled by this region. Cats
with lesions in this area act out their dreams!
The hypothalamus controls the sw
itch between waking and the two kinds of
sleep. Narcoleptics have abnormalities in this area.
The importance of sleep is clear to most people. Every
human alive needs approximately 8 hours to function “normally.”
But neu
roscientists don’t exactly know why we need to sleep.
What we do know is this: humans die without it. Sleep is
evolutionarily important, too, aiding in memory consolidation, energy
conservation, avoidance of predators, and body restoration.
