Functions of Sleep
"Works Cited Missing"
Sleep serves an important function as we spend about one third or our
lives asleep. Theories of why we sleep can be separated into two
explanations Restorative theories, and Ecological theories.
The restoration theory claims that sleep enables the body to make
repairs after the exertions of the day. Evidence for the role of SWS
comes for the hypothesis that if SWS serves the purpose of repairing
the body then physical exercise
should lead to more SWS.
Shapiro et al
. (1981) studied the sleep
patterns of long distance
runners. After a 57 mile race they found that the runners slept 1.5
hours longer than normal on the 2 nights following the race. In
particular, there was an especially large increase in the amount of
time devoted to SWS. However, Horne & Minard (1985) did a more
controlled lab study and found that sleep length was not affected by a
series of exhausting cognitive & physical activities. The participants
went to sleep more quickly but with no increase in sleep duration.
Further evidence for restoration theory comes from total sleep
deprivation studies. Instead of targeting either REM or SWS these
studies involve the participant not sleeping for as long as possible.
Participants were volunteers and it was also a small sample.
Therefore, the findings of the research cannot be generalised to the
Oswald observed patients recovering from injuries to their central
nervous system. He found an increase in the quantity of REM sleep
which suggests that there was a recovery process going on in the
brain. There is also a correlation in the quantity of REM sleep and
brain weight increase in newborn babies, their rapid brain growth is
due to their long REM sleep.
The restoration perspective also states that sleeping is a way of
conserving and making important neurotransmitters. These are important
to our alertness during the day as it helps the transmission of nerve
impulses. As time passes during the day, neurotransmitter levels fall.
During REM sleep neurons synthesise new neurotransmitters for release
during the next day. However REM sleep involves neural activity,
therefore is unlikely neurotransmitters are being restored as it is
more likely it is being used up during REM sleep.
Peter Tripp stayed awake for 9 days. Three days into the experiments
he became abusive, day 5 he began to hallucinate and became paranoid.
By the end of the experiment Tripp’s body temperature had fallen and
his brain wave patterns were almost the same as a sleeping person’s
brain. After 24 hours he reported himself to feel perfectly fine.
Randy Gardner stayed awake for 11 days, unlike Tripp he didn’t display
any psychotic symptoms during his time awake and appeared normal after
Both Tripp and Gardner showed that going without sleep for a long time
has no serious long term damage. They also showed that it isn’t
necessarily important to recover all the sleep lost. However this
study is based on individuals with unique characteristics therefore
cannot be generalised to the rest of the population and also their
conditions wasn’t controlled. Williams et al. said that when people
are deprived of sleep for more than 72 hours they have short periods
of microsleep which is just like normal sleep. Therefore Tripp and
Gardner could have actually gotten sleep without it being noticed.
The ecological perspective is based on observation of animals in their
environment. Webb claims that the function of sleep is similar to that
of hibernation. In other words, a sleep mechanism has evolved to force
us to conserve energy at times when we would be relatively inefficient
to guarantee that we would save energy and be protected at night.
Similarly, Meddis (1975) claims that sleep behaviour depend on the
need to adapt to environmental threats and dangers. In the case of
species that depend on vision it is adaptive for them to sleep during
the hours of darkness.
Animals don’t conserve much more energy when sleeping then when
resting; sleep reduces energy rates by 5-10%. This suggests that rest
would be as adaptive as resting. The energy conservation explanation
is not sufficient enough to explain the function of sleep. The
unilateral sleeping habits of marine animals such as dolphins indicate
that sleep function can be satisfied when the animal is partially
active. This suggests that conserving energy cannot be the key
adaptive function of sleep.