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Describe and evaluate two theories of sleep (

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Describe and evaluate two theories of sleep (24 marks) When people are asleep there are not in a total loss of consciousness but a gradual reduction in awareness. Sleep occurs in stages and they are started of by the alpha stage this is where there is smooth electrical activity and this is seen as a state of relaxation as there is slow heart rate and reduction in muscle tension. The second stage the beta stage is where there is irregular electrical activity and this is associated with a state of arousal the Person can also be woken easily. Theta activity is associated with an EEG (electroencephalograph) and this occurs during early stages of slow wave sleep and REM sleep. The last stage of sleep is delta activity this is where there is regular electrical activity and occurs during the deepest stages of slow wave sleep and people in this stage of sleep are hard to wake and hormones are also secreted round about now. The EEG is an objective measure of sleep it shows the electrical activity of the brain. There are different patterns of activity at different times during sleep without these researchers would have to rely on subjective measures such as asking people to self report. The Restoration theory focuses on restoring tissue and saving energy. ...read more.


From this both physical and brain protein synthesis are dependant on growth hormones which are secreted after the first bit of delta activity in slow wave sleep. The second theory is the evolutionary theory this has two parts to it the conservation part and the protection part. Meddis (1979) suggested that in order for animals to protect themselves they would sleep and this would increase there chances of safety as the animals would be immobile and therefore would be less likely to be noticed by predators. An example of this would be the sleeping pattern of dolphins. The dolphins in the River Indus only sleep for a few seconds at a time repeatedly through 24 hours. Marine dolphins only sleep with one hemisphere at a time showing that they do this to protect themselves from predators, the theorist Webb (1982) supported the view that sleep helps to conserve energy but also thought it allowed animals to become more aware of an able to avoid predators. Apart from looking at marine animals it's clear to see animals that graze such as sheep need little sleep as they are vulnerable and need to eat in order to gain energy and also it makes them more vigilant as they are moving about a lot more and can attract the attention of predators. ...read more.


Melatonin plays a role in the co-ordination of the sleep wake cycle. So as sleep isn't affected by light then the cause of insomnia can't be known as you can't determine what effects the body that causes insomnia. REM sleep involves an increase in energy expenditure and blood flow which inhibits protein synthesis on the other hand it is known that amino acids are not stored by the body and last in the body for bout 4 hours after a meal. This means that protein synthesis maybe stopped half way through sleep because the amino acids have run out. Also people will sleep more after stress and it is known to improve moods which again can be explained by the fact that with NREM sleep occurring during slow wave so enables the body to repair itself and there is an increase in secretion of growth hormones. By looking at the evolutionary theory I can also conclude that the arguments presented for the evolutionary theory contradict themselves as some suggest that some animals sleep less to keep a vigil while others suggest that animals sleep longer to keep motionless thus staying away from harm. Also it is clear to see that animals such as lions do sleep longer as they are at less of a risk from being hunted so don't need that much sleep and animals like cattle need very little sleep and this puts them in danger of being hunted. ?? ?? ?? ?? Saira Afzal ...read more.

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