Sleep States

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  • Sleep States
    • Sleep Stages
      • Dement & Kleitman: showed 2 types of sleep associated with brain wave patterns alternate in ultradian rhythm. Rapid Eye Movement sleep & Non-REM called Slow Wave Sleep.
        • SWS: has 4 different stages.
          • Stage 1: occurs when falling asleep. Lasts 15 mins.
            • Brain waves slow down from slow alpha waves of relaxation to even slower more irregular theta waves.
            • Heart rate slows, muscles relax, hypnogogic phenomena may occur, wake without realising we nodded off, easiest stage to be woken from.
          • Stage 2: lasts 20 mins.
            • Theta waves get larger & slower with intermittent little bursts of activity called sleep spindles.
            • Heart rate, blood pressure & body temp continue to fall. Quiet sounds no longer wake us.
          • Stage 3: lasts 15 mins.
            • Brain waves slow more into delta waves with some sleep spindles.
            • Heart rate & breathing falls. Hard to be woken.
          • Stage 4: lasts 30 mins.
            • Brain waves at its lowest.
            • Deepest sleep, difficult to be woken. Growth hormone secreted, metabolic rate low, sleep walking most likely to occur.
        • REM: lasts 10 mins- 1 hr.
          • Also called paradoxical sleep as body is paralysed to prevent body acting out dreams & endangering life.
          • Eyes twitch. Heart rate, blood pressure & body temp increase. Almost impossible to be woken.  Dreams most likely to occur.
          • Brain very active. EEG pattern changes to high frequency.
          • Most of 2nd half of the night is spent in REM.
    • Life span Changes
      • Infants: Sleep more than adults (16 hrs a day, 50% in REM). Sleep cycles shorter than adults. At around 6 months develop a circadian rhythm.
      • Old people: Sleep less (20% less REM, 9% less SWS). Increased risk of sleep disorders. Phase advance is common. Usually wake during the night & nap during the day.
    • Functions of Sleep
      • Restoration Theory
        • Oswald: suggests high level brain activity in REM reflects brain recovery, REM is essential for brain repair. Increased hormone activity (growth hormone in SWS) reflects restoration & recovery in the body. Function of sleep is to restore body & brain.
        • Horne: suggests function of sleep is to rest & recoperate in order to restore body to its fully waking capacity. Stated core sleep is stage 4 SWS & REM whereas lighter stages of SWS are optional.Believes body restoration occurs in periods of relaxed wakefulness.
          • Contradict :. complex idea.
            • Oswald: suggests high level brain activity in REM reflects brain recovery, REM is essential for brain repair. Increased hormone activity (growth hormone in SWS) reflects restoration & recovery in the body. Function of sleep is to restore body & brain.
          • Stern & Morgane: propose REM is specifically for rest of neurotransmitters. Observed REM dep & found p.s showed REM rebound.
          • REM & brain repair idea  supported by babies having  50% of their time in REM.
        • Effects of energy expenditure.
          • Breedlove et al: intense exercise causes people to fall asleep more quickly but not for longer. Theory does not explain this.
          • Sloths sleep for 20 hrs a day and energy expenditure is small. Goes against theory.
        • Body function & sleep deprivation:
          • Horne: reviewed 50 studies into human sleep dep, found very few reported that dep interferred with ability to perfrom physical tasks & no evidence of psysiological response.
            • Horne concluded sleep in noraml p.s only had mild effects (Garrdneer) with sleep recovery concentrated mainly in stage 4 SWS & REM.
          • Tripp: case study deprived of sleep for 200hrs & after 3 days became very aggressive, during period REM should have occured experienced hallucinations. After he slept for 24hrs & hallucinations topped, returned to normal but  marriage ended shortly after, wife said he had changed.
          • Gardener: Case study deprived for 264hrs, showed  no side effects.
            • Shows great individual difference.
              • Tripp: case study deprived of sleep for 200hrs & after 3 days became very aggressive, during period REM should have occured experienced hallucinations. After he slept for 24hrs & hallucinations topped, returned to normal but  marriage ended shortly after, wife said he had changed.
          • Everson et al: found sleep dep in rats cause them to increase metabolic rate & die within 19 days. But methodological issues & issues with use of animals.
        • Growth hormone & sleep.
          • Horne: points out amino acids are only available 5 hrs after eating, most people sleep several hrs after eating :. supply of amino acids is low for most of the night so not much protein synthesis can occur.
        • Animal variation.
          • If sleep was for restoration surely all animals should sleep for the same amount of time. Evo approach & theory contradicts Rest theory.
      • Evolutionary Theory
        • Webb: suggests sleep forces us to conserve energy in times when it is ineffecient for us to be awak (darkeness). Mammalian bodies fall by 1 or 2 degrees when asleep saving a bit of energy, & increase sleep time when food is scarce.
        • Meddis: proposes sleep is a time of incresed safety as mammals are immobile & :. less likely to be noticed by predators. Difficult to stay still for long periods so sleep avoids unwelcome attention. States different animals sleep for different amounts of time depending on safety of sleeping habitate & on how much time they need to spend gathering food.
        • Animals & sleep.
          • Empson: points out sleep is universal amoung all animals, even most succesul predators so must have a higher function.
          • Theory focues on animals so problems with validity & generalisation to humans.
            • If sleep is beneficial due to being quiet why do so many humans sleep noisily eg snore, sleep talking/walking.
          • Nocturnal animals sleep during day so do not fit theory.
            • However their sleep patterns have developed to fit their way of living due to safe environment.
        • As an adaptive approach.
          • If sleep is to keep anials out of harms way surely it is safer to remain inconspicuuous but awake rather than asleep.
          • If sleep merely served as an adaptive function surely it would have been wliminated through the process of natural selection.
        • Sleep deprivation.
          • Empson: pointed out sleep dep is fatal so is not merely an adaptive function.
            • Rechtshaffen: found rats died after 33 days of total sleep dep.
            • Jouvet: used flower pot technique which deprives animals of REM, found animals died after 35 days.
  • Ethical issues: sensitivity as sleep dep can cause cognitive inabilities.
  • Gender & Culture bias: (beta & etic constructs) Theory assumes fuction of sleep is same or all gender & culture but Tripp & Gardener show ind diff occurs even within the same gender & culture.
  • Evolutionary Approah: reductionist. contradicted by rest theory.

Comments

MrsMacLean

This is excellent, very detailed. Thanks 

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