Biological Rhythms and sleep

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  • Created by: bethany
  • Created on: 03-04-13 21:19

Circadian Rhythms

  • consistent cyclical variations
  • 24 hour time period
  • eg, our sleep-wake cycle/body temperature
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A01 Description

The circadian rhythm is determined by an internal 'biological clock' (endogeneous pacemaker), but can also be influenced by exogenous zeitgebers.

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A01 Research

  • Siffre spent 6 months in a cave, no exogenous zeitgebers. His sleep wake pattern remained cyclical, however his day lengthened to c.25 hours. Therefore, environmental cues that resets the bio clock to 24 hours.
  • Folkard et al studtied 6 students, 1 month, isolated all external ces. F 25 hour internal bio clock.
  • Folkard et al, study where he altered environmental cues. isolated 12 people from any external time cues, apart from a clock that initially ran at the correct time, but eventually shortened to 22 hours. Only one ppt managed to keep up with the clock, going to bed at 11.45 pm and waking at 7.45 am. Therefore people have a strong biological clock.

Environmental factors can also entrain our body clocks. Research has shown that regular feeding, excercise and social interacytion can be effective EZ for hamsters.

  • Inuit eskimos live in constant daylight in the summer and darkness during the winter yet still have regular sleep wake cycles, showing that endogenous pacemakers are very strong, but also there are other important EZ influencing the CR.
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Endogeneous pacemakers

  • When it gets dark, the retina in the eye sends messages to the SCN.
  • This information is transmitted to the Pineal gland.
  • The Pineal gland begins to secrete melatonin (sleepy).
  • Melatonin in turn, influences the ralphe nuclei which produce the neurotransmitter serotonin.
  • Increased levels of serotinin in the brain increase sleep.
  • Serotinin then influences activity in the RAS, which is assoicated with the onset of sleep and arousal from sleep.
  • Therefore the pineal gland and SCN function as EP in the brain controlling our sleep-wake cycle.
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A02 Research supporting role of SCN

  • Stephan and Zucker - F that damage to the SCN in animals causes irregular patternd of behaviour including the sleep wake pattetn.
  • Ralph et al - transplanted the SCN between hamsters with different free running CR. First, the scn was removed from mutant hamsters 'designed to run on a 20h rhythm. Then the SCN's were transplanted into the brains of other hamsters with a free runing 25hour rhythm. Both adopted the other rhythm. CR T linked to SCN in our brains.
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A02 Research supporting role of melatonin

  • If people take a dose of melatonion in the afternoon, they fall asleep earlier and wake earlier. This is called phase advance effect on the bio clock.
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Nature Vs nurture - mainly, as even without EZ remians cyclical, however an element of nurture.

Biological approach

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Infradian Rhythms

Consistent cyclical variations asting longer than one day, eg menstruation (28 day cycle), breeding and migration in animals or SAD.

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A01 Research

  • Russell et al - Collected daily samples of female sweat (an Exogenous zeitgeber), and rubbed it into the upper lip of other women. It was found that the women's menstruation cycles became synced with their donors.
  • Reinberg et al - studied mensturation in the absences of EZ, in particular light. Young woman, cave, 3 months. F her day lengthend to 24.6h, and her MC shortened to 25.7 days.
  • Pengelly and Asmundson - studied 5 squirrels born into captivity and blinded at birth who were isolated from exogenous zeitgebers. The squirrels were kept in constant darkness, temperature and food was continuously available. It was F that the animals still hibernated ar roughly the same time they would in the wild. Therefore bio clock = important
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(I) ethics - animal, eg Pengelly and Asmundson

(A) Biological

(D) free will vs determinism

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Ultradian Rhythm

Consistent cyclical variations shorter than one day, eg BRAC or the cycle that occurs during sleep.

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Sleep Wake Cycle (Stages)

  • Rechtscaffen and Kales measured elctrical activity of the brin with an EEG finding fidderent patterns of actvity at different times of sleep. Sleep has been divided into four sequential stages and also REM sleep.
    • Stage one - Alpha Waves disappear and are replaced by slow waves, the heart rate slows and also muscles relax. At this stage individuals are easily woken.
    • Stage two - This stage is deeper than the first, and bodily functions further slow, blood pressure also decreases.
    • Stage three - People become difficult to wake at this point, and bodily funtions further decrease.
    • Stage four - A deep stage of sleep, growth hormones are released and incidence od sleep walking and night terrors may occur.
  • 40 min to get to S4, 1 to 4 then 4 to 2 to REM.
  • C. 5 ultradian rhythms a night.
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Sleep Wake Cycles (REM)

  • Characterised by very rapid eye movements that can be observed through closed eyelids. Beta Waves in the brain resemble those observed when people are alert and awake. Heart rate, blood pressure and breathing increase. This is when dreaming takes place.
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What causes REM sleep

The locus coeruleus in the brain produces tje neurotransmitters noradrenaline and acetylcholine. Rem sleep occurs when there is an increase in acetylcholine, and ends with increases in noradrenaline.

  • Monaamine oxidase inhibitors increase levels of noradrenaline and serotonin and liminate REM sleep.
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A02 Research

  • SR - Dement and Kleitman - moonitored electrical brain activity during sleep using an EEG and woke ppts at different stages of sleep. Ppts reported feelings/emotions/experiences and it was found then when ppts were woken during REM sleep 90% recalled dreaming, compared to only 7% of the time in non-rem sleep. (dream = rem sleep)
  • CR - some studies have reported a 70% recall rate of drems in non rem sleep. But folkes has argued that this is due to dream like experiences being confused and incorrectly categorised.
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  • (I) animals - generalise
  • (A) Biological
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Life span changes

  • Foetus - at 40 weeks REM sleep = 50% of time.
  • New born, will enter REM sleep immediate and at 3 months rem non-rem sequence develops, the baby will sleep for 16 hours a day.
  • Between 5-12 total night sleep has halved to 9 hours, and children sleep very deeply. At this age one ultradian rhythm is c.70 minutes.
  • As a young adult 18-30 , 53% of people report daytime sleepiness (q'aires) and are also likely to sleep less deeply.
  • At 45 to 60 years of age people tend to experience a pooror quality of sleep, and duration of sleep is about 7 hours a night, whilst the time spent is S4 of sleep reduces.
  • By 60 total time a sleep at night is 5/6 hours, and S3/4 is reduced and so by this ages we spend of our time in this state as we did when we were 20.
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Life Span changes A02

  • Borbely et al - questioned adults ages 65 to 83 years of ages and F that 60% reported taking frequent naps. T these may infact account for the reduced sleep times recorded at night.
  • Little researcg into normal sleep among the middle aged. Dement believed that this is because people of this age are too busy to volunteer for sleep research.
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Free will vs determinism

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Shift Work

Shift work can involve working at a time people normally sleep, and this can cause break downs in the usual coordination between bio pacemakers and exog zeitgebers.

Many SW change weekly T they are in a permanent state of desynchronisation with the individual having to continually change their sleep wake pattern causing symptoms uncluding tiredness, headaches and illness.

The natual free running biological clock is 25 hours and therefore it is easier to mak changes that lengthn the day, as a result it is easier to move a shift forward, called phase delay.

Research has shown that the consequences of regularly changing shifts can have serious psychological and physical health of individuals, but also increases the chances of accidents, aswell as reducing the productivity of the company. Approximately 20% of shiftworkers report falling asleep during work increasing the rsk of accidents and reduce productivity. Such accidents include Chernobyl which ccured at 1.23am.

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A02 research

  • Cooligan et al - f that workers with shift rotations had more accidents than workers on set shifts. Also had higher alchol consumption, took sleeping tablets more commonly, and less successful relationships.
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(A) mainly Biological, elements of behaviourist with EX Zeitgebers. T interactionist (a)

(I) a lot oof research is conducted on male ppts, (more involv in shift work) therefore research can be seen as gender biased, with the results not being necc being representative of females.

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Reducing the effects of Shift Work

  • Gold et al - f that workers who always worked the night shift had less probems than those who worked a rotating shift a pattern
  • Czeisler et al - recommeneded that shifts rotate forward to take advantage of the body's natural preference for a slightly longer day. After these changes workers reported better health, increased productivity and a decrease of errors leading to accidents.
  • Sharkey - Bio adjustment to shift patterns can be speeded up with the use of melatonin.
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Jet lag

The world is divided into 24h time zones centered around London, and there are bioloigcal implications of corssing time zones in a short spaces of time, for example by flying that causes tiredness during the 'new daytime' having consequences such as loss os appetitie, indigestion and poor mental performance.

PPeople suffer less jet lag symptoms when  travelling west than east as this lengthens the day and the natural CR = 25h.

  • Recht et al - visiting baseball teams who did not have to cross time zones between one game and another won 46% of their games, but when teams travelled east to west they won on average 44% , and west to east 37%.
  • Harma and Suvanto - examined the effects of a 4day flight across 10 time zones. 40 female ppts reported their subjective sleepiness and sleep quality. Also their alertness and performance of visual tasks were monitored. F - sleepier over 4 days, quality reduced aswell as, melatonin level and body temp = desynchronised.
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Free will Vs Determinism - you will have consequences

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Reducing the effects of Jet Lag

  • Melatonin is produced mainly at night. After a long flight, the cyclical release of melatonin remains on the day night pattern of the home country for days led to fatigue during the day and insomnia during the night.
  • Blakemore tested this drug and found fewer people were jet lagged than those who had taken a placebo.
  • Another study, a meta-analysis of 10 studies F that 90% of ppts reported decreased jet lag when taking melatonin compared to placebos.
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Function of sleep - Evolutionary

Sleep  = adaptive advantage to animals, otherwise bhav extinct overtime. Two theories within the Evol expl have been developed; the predator avoidance theory and the Energy onservation.

Meddis developed the PA theory and suggested preyed upon animals have fewer hours sleep that predatory animald as they are not as safe when sleeping. He proposed that sleep simply ensures animals stay still when they have nothing better to dowith their time and danger is most likely to occur. Ancestors = primativie conditions, makese sense for them to stay still when they would not be able to see and would be easy prey, but also to reduce the chance of injuring self.

Webb developed the Energy conservation theory, and said that animald with a high metabloic rate use up more energy and thus need to sleep longer as a means of energy conservation. Hobson further argues that since the likelihood of finding food at night is reduced, more energy would be used hunting than gainef by the result of hunting.

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Evaluation of the evolutionary explanation as to w


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(A) biological

(D) deterministic

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Funtion of sleep - restoration

This is split into two theories; restoring the body and restoring the brain.

  • Oswald - f tissue growth of new skin cells to take place during sleep. Also f high levels of ATP (and neergy currency cell) during sleep
  • Shaprio - f people who had completed a marathon during the day slept an hour and a half longer for two nights following
  • Horne - meta-analyis, 50 sleep deprivation studis and f vert few claimed sleep deprivation had affected ppts ability to perform physical excercise. He sugg instead that 'core sleep' was essential for normal brain functions and cognitive abilities.
  • Dement studied REM sleep deprivation in cats by placing them on upturned flower pots in surrounding water. When the cats entered REM sleep their postural muscles relaxed and they fell into the water causing them to wake up, the cats would climb back on the pots, and the process began again. After 35 days the cats died
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A02 research

  • Lavie studied the effects of total sleep deprivation for 200 hours under controlled conditions with several ppts and f no long term detrimental effects, however each night brought worsened symptoms that included confusion, irritability and problems processing information.
  • CR, also conducted by Lavie who conducted a case study on a man who only slept 15 minutes a night, but was competent with all brain functions
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(A) Biological approach

(d) reductionist

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Sleep disorders - Sleep walking (A01 description)

Sleeping walking effects approx 10-18% of the population, sleep walkers behave automatically and do not respond to their environment, their eyes are sometimes open, but they do not see. 

Most sleepwalking occurs in staged 3 and 4 (non rem sleep) and happens early in the night. Sleep walkers are therefore not acting out a dream, but performing well rehearsed automoatic responses. Lavie described a 6 year old boy who go out of bed in a sleep laboratory and preceeded to walk as far as he could (constrained by EEG monitors) and stand, waving his arms in the air. It was later discovered he was practising out his part in a school play where he had been the sun.  

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Sleep Walking - A01 influences

Genetic influence 

  • Broughton f - the prevalence of sleep walking in first degree relatives is at least 10 times greater than the gneral population. 
  • Lecendreux et al f - 50% CR in MZ twins compared to 10-15% CR in DZ twins

Environmental factors - there have been environmental factors as well as biological ones linked to the causes of sleepwalking, such as stress, alcohol and sleep deprivation.

  • Zadra et al carried out a study involving 40 sleepwalkers at a sleep research centre in Montreal. They f a strong + correlation between the amount of sleep deprivation and the likelihood they would sleepwalk. 
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Sleep walking A02 research

Genetic influence

  • Lecendreux et al (2003) compared 60 ppts from families with a history of sleepwalking with a group of ethnically matched non sleepwalkers and found a genetic marker that was related to sleepwalking. This therefore supports the idea that there is a gentic cause for the development of sleepwalking. 

Environmental factors - sleep deprivation (Zadra)

  • Dement observed that sleepwalking tends to begin at around 4 years old. This is also the time that children start to stop having naps and may therefore, in effect be sleep deprived. 
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Sleep walking A02 research

Genetic influence

  • Lecendreux et al (2003) compared 60 ppts from families with a history of sleepwalking with a group of ethnically matched non sleepwalkers and found a genetic marker that was related to sleepwalking. This therefore supports the idea that there is a gentic cause for the development of sleepwalking. 

Environmental factors - sleep deprivation (Zadra)

  • Dement observed that sleepwalking tends to begin at around 4 years old. This is also the time that children start to stop having naps and may therefore, in effect be sleep deprived. 
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(D) one debate that can be applied to the theory of sleep walking is the natur vs nurture debate. The theory takes into account both sides of the debate, thus making it an interactionist theory. It considers that there may be a gene that causes sleep walking supporting the nature side of the debate, but also acknowledges there may be environmental factors, such as sleep deprivation that can cause sleep walking to occur therefore also supporting the nurture side of the debate.  (A) Bioloigcal approach  (A) Behaviourist approach 

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sleep disorders - narcolepsy A01

This is where an indv  falls instantly and involuntarily alseep. It affects approx 1/2000. It is often associated with a sudden loss of muscle tone causing the person to collapse, sleeping for two to twenty minutes, before the person awaked feeling refreshed. The indv goes immediately into REM sleep suggesting the disorder arises from poor control of the neural mechanisms that trigger REM sleep. 

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Narcolepsy - influence

Genetic influence

The incidence of narcolepsy varies considerably between ethnic groups, eg in Europe it affects 0.05% of the population but the % is nearer to 2 in Japan. This could be considered evidence to suggest that N is the result of genetic differences that can be passed through familes. 

However, the most likely explanation for narcolespy is that the individual has a shortage of the neurotransmitter hyprocretin, which is involved in the control of wakefulness and sleep. Chemelli et al produced genetically modified animals with narcoleptic symptoms caused by an absence of hypocretin.

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Narcolepsy - A02 research

Contradictory research to the theory that narcolepsy runs in families, was by Mignot who found narcolesy to not run in families, and it has also not been found to be concurrent in twins where one has the disorder. 

Mishmina et al provides SR  to the idea that narcolepsy is related to reduce hypocretin levels. She f that there were mutations to some of the genes in narcoleptic animals and humans, which are involved in the production of receptors for the hypocretins. 

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(I) animal research - unethical, eg Mishmina. 

(D) diathesis stress model

(A) bioloigcal 

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Sleep disorders - Insomnia A01 (PI)

Insomnia = the inability to fall asleep or stay asleep. It is defined by the indv perception of sleep quantity and quality. 

There are two types of insomnia, primary, when the reason for not being able to sleep is unknown and seconary insomnia, when there is a known reason for not being able to sleep. 

One type of primary insomnia is a form of anxiety induced insomnia where a vicious cycle is set up. As a person tries harder to sleep, they become more anxious about sleeping. This in turn makes it harder for the indv to sleep, and this worry is carried on until the next day when they try and sleep again. Indv with this type of insomnia also have a preoccupation with sleeping. 

MacMahon et al S a preoccupation with sleeping. Using an independent g design, he f that indv with PI showed greater attention to sleep related stimuli than ppts with delayed sleep phase syndrome. He concluded that cognitive facotrs are therefore important to this illness. 

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Sleep disorders - Insomnia A01 (SI)

Secondary insomnia and food

  • Lichstein et al asked a random sample of 772 ppts to complete sleep q'aires, keep a two week sleep diary and to also report nutritional supplmements they were taking, it was f those using vitamin supp had poorer sleep and higher rates of insomnia that those who were not talking the tablets. 

Genetic vulnerability to insomnia, so it is passed from parent to child

  • Beaulieu et al, reported 34% of insomniacs surveyed said they has a first degree relative with/or have a history of insomnia. 
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Insomnia A02 research

Primary insomnia

Secondary insomnia 

  • Food and Insomnia - Kahn et al f children with a milk intolerance had increased sleep after eliminating milk from their diet. 
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(A) Overall research into insomnia can be seen as holitic in it's approach as it considers a wide range of influences, both physioloigcal and psychological, such as as environmental influences such as food and genetic causes. 

(D) nature v nurture, interactionist

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