People generally sleep because they are tired, suggesting that sleep is fundamentally fro
rejuvenation and repair. Growth hormone is released during sleep, stimulating tissue growth and
aiding proten synthesis, used to repair damaged tissues. Waste products are also removed.
Oswald's (1980) restoration theory. This explaination sees
sleep as helping to reserve and/or restore biochemical and/or
physioloical processes that are progresssively degraded
during the day. In essence it suggests that being awake
disrupts the homeostasis of the boy and that sleep is required
to resotre it. High levels of brain activity during REM sleep
indicate brain restoration, while growth hormone production
during the four stages of SWS indicate bodily resotration and
repair.
Horne's (1988) core sleep model; as many resotration processes, such as
digestion actually occur while awake, with some occuring more during
wakefulness than when sleeping - Horne concluded that sleep does not provide
any repair functions in humans , except for the brain. Horne referred to core
sleep , which he believed is essential for restoration, whereas other types of
sleep he called optional sleep, whose main purpose is energy conservation.
stage 4 and REM sleep are seen as necessary for the healthy brain functioning
required for cognitive processing; during these stages the brainis seen as
refreshing and resotring itself, ready for the challenges of the new day.
Adam (1980) reported that many restorative processes, like digestion, do occur during sleep,
supporting the restoration explaination.
Cirelli et al (2004) found that during SWS, genes associated with the protein production
regulating synaptic connections are activated, supporting restoration theories especially Oswalds.
Shapiro et al. (1981) found that long distance runners tend to sleep for longer
than normal suggesting that sleep does aid restoration.