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| Science Forum Index » Bio Evolution Forum » Why do we sleep?... |
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| Tom Hendricks... |
 Posted: Fri Sep 11, 2009 8:39 am |
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Guest
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There are many ideas on why we sleep. Here is mine. It is based on
looking at life as somewhat separate evolved catabolic and anabolic
pathways. See my other posts. I think this way of looking at
biochemistry can give a lot of insights.
First there are some things everyone recognizes about sleep:
1. Sleep is VERY important. Whether its fruit flies, fish, cats or
humans , whether its seals and dolphins that sleep with alternate
hemispheres of their brains asleep, or bears hibernating during the
winter. No matter the way the creature sleeps, we know that without
sleep it can die. Sleep has got to be something very important.
2. There are two main parts to sleep:
NREM , not random eye movements, or slow wave sleep, or deep sleep
where the brain is less active. Most of sleep is in one aspect of the
stages of NREM sleep.
And REM, rapid eye movement sleep. REM sleep seems to have a lot of
dreams. REM sleep makes up about 20% of total sleep time.
Here's my idea:
Sleep is the 2nd half of a daily metabolism cycle. Waking is mostly
catabolic digestion. Sleep is mostly anabolic absorption and
assimilation.
Specifically NREM sleep is more involved with replenishing the body
with absorption and assimilation of nutrients, and REM sleep is more
involved with preparing waste out to end the daily digestion cycle.
Then we wake up and repeat the process.
Note that insomnia seems to be caused by excessive metabolic activity
in the brain's frontal cortex. And that sleep problems often lead to
weight problems - specifically Less REM sleep associated with
overweight. And that lack of sleep increases the level of cortisol a
hormone that increases a person's hunger. And perhaps most importantly
during NREM sleep there is a decrease of catabolic hormones and an
increase of anabolic hormones.
There is a lot on the web about sleep. For example, this website
shares many of the ideas that I've suggested, though we differ too.
http://www.chemistrydaily.com/chemistry/Sleep
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