Psychology Sleep Chapter Summary
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- Created by: Ella Green
- Created on: 10-05-14 18:27
Circadian Rhythms Summary
Sleep-wake cycle:
- Circadian = 24 hours
- Cycle persists despite isolation from light
Evaluation:
- Participants not isolated from artificial light in early research
- Demonstrated by Siffre and Aschoff and Weaver
- External cues important too (Folkard et al)
- Cycle length varies in individuals
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Circadian Rhythms Summary
Core Body Temperature:
- Lowest at 4:30am
- Highest at 6pm
- Post-lunch dip, even without food
Evaluation:
- Linked to cognitive abilities (Folkard et al)
- Evidence that change is caused by temperature (Giesbrecht et al, 1993)
- Other research sugest link is spurious
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Circadian Rhythms Summary
Hormones:
- Cortisol = lowest at midnight
- Melatonin and growth hormone = highest at midnight
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Circadian Rhythms Summary
IDA:
- Biological and deterministic
- Real world application - chronotherapeutics
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Infradian and Ultradian Rhythms Summary
Ultradian Rhythms:
- Less than one day
- First four stages of sleep = NREM
- Fifth stage = REM
- BRAC = 90 minutes within 24 hour rhythm
Evaluation:
- REM does not equal dreaming
- BRAC = important because it ensures biological processes work in unison
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Infradian and Ultradian Rhythms Summary
Infradian Rhythms:
- Female menstrual cycle regulates ovulation
- Males have 20 day cycle of body temperature and alertness
- SAD = caused by melatonin during winter months
Evaluation:
- Menstrual cycle = subject to exogenous cues
- PMS
- SAD could also be consequence of disrupted circadian rhythms
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Infradian and Ultradian Rhythms Summary
IDA:
- Determisitic but can change through willpower (Born et al)
- Real world application = phototherapy
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Endogenous Pacemakers and Exogenous Zeitgebers
Endogenous Pacemakers:
- SCN = main endogenous pacemaker
- Contains protein mechanism
- Pinal gland controls melatonin secretion
Evaluation:
- SCN evidence = 'mutant' hamsters (Morgan)
- Desynchronisation can lead to symptoms of jet lag
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Endogenous Pacemakers and Exogenous Zeitgebers
Exogenous Zeitgebers:
- Light is dominant zeitgeber
- Social cues also important
- Biological rhythms can be entrained by temperature
Evaluation:
- Artificial lighting may also reset biological clock
- Failure of biological clock leads to sleep-phase disorders
- Biological clck is really a blend of endognous and exogenous factors
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Endogenous Pacemakers and Exogenous Zeitgebers
IDA:
- Non-human animal studies
- Ethics and relevance
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Lifespan Changes
Children:
- Babies sleep 16 hours a day, but not continuously
- Shorter sleep cycles than adults
- Circadian rhythm established at six months
- At 5, sleep patterns like those of adults
- May experience parasomnias
Evaluation:
- Sleep differences in babies - adaptive (for parents)
- Immature brain
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Lifespan Changes
Adolescence:
- Need for sleep increases (9-10)
- Circadian rhythms change
- Slight phase delay
Evaluation:
- May be linked to hormone production
- Implications in school day
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Lifespan Changes
Adulthood and Old Age:
- Increase in sleep disorders
- Patterns of sleep changes in old age
- Reduction in REM and SWS
- Older = phase advance effect
Evaluation:
- Increased mortality rate with too much sleep (Kripke et al)
- Sleep deficit in old age may explain impaired functioning in other areas
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Lifespan Changes
IDA:
- Developmental Approach
- Cultural bias (overlooked)
- Real-world application
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Restoration Explanations
SWS:
- SWS = stages three and four
- Growth hormones secreted during SWS
- Decline of GH in older age = reduced SWS
- Lack of SWS = low immune functioning
REM:
- Important for brain growth
- Restoring neurotransmitter sensitivity
- Link between REM and procedural memory
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Disruption of Biological Rhythms
Shift work and Shift Lag:
- Nightworkers experience 'trough' of decreased alertness
- Sleep deprivation due to sleeping problems during the day
- Relationship between shift work and organ disease
Evaluation:
- Shift work effects not solely due to disruption of biological rhythms
- More problems with rotating shifts
- Forward rotating less harmful
- Artificial lighting can eset rhythm but not dim lighting
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Disruption of Biological Rhythms
Jet travel and Jet lag:
- Caused by disruption of circadian rhythms
- Phase delay less disruptive than phase advance
Evaluation:
- Jet lag symptoms may be caused by other factors
- Melatonin may reduce symptoms
- Social customs also help
- Individual differences exist in coping with disruption
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Evolutionary Explanations:
Energy Conservation:
- Period of inactivity to conserve energy
- Essential for animals with high metabolic rates
Foraging:
- Herbivores spend less time sleeping
- Carnivores more because food rich in nutrients
Predator Avoidance:
- Sleep constrained by predation risk
- Predators sleep more, prey sleep less
Waste of time:
- Staying still at times when an animal cannot forage
- Subject to predatation
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Evolutionary Explanations:
Evaluation:
- Evidence about animal sleep patterns incomplete
- Evidence suggests that species with a higher metabolic rate sleep more
- Evidence suggests that species with higher predatation risk sleep less
- Evidence to support foraging and predator avoidance
- NREM evolved first for energy conservation
- Then REM to maintain brain activity
- Phylogenetic signal supports evolution of sleep patterns
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Evolutionary Explanations:
IDA:
- Evolutionary approach can be combined
- Restoration using core and optional sleep
- Horne (1988)
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Explanations of Insomnia
Short term Insomnia:
- Caused by worry, noise, jet lag or temporary medical conditions
Long term Insomnia:
- Primary = not associated with medical conditions
- Secondary = symptom of a medical disorder or some other issue
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Explanations of Insomnia
Evaluation:
- Diagnosis has implications for treatment
- May be cause rather than effect
- Consequences include cognitive impairment, accidents, psychological disturbance, anxiety disorders or immune system underfunctioning
- Predisposing factors (genetics)
- Precipitating factors (environemental stressors)
- Perpetuating factors (expectations)
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Explanations of Narcolepsy
- Psychological (Disguishing sexual fantasies)
- Early explanations = failure of REM regulation
- HLA mutation causes reduced immune system functioning
- Low levels of neurotransmitter hypocretin in hypothalamus affects wakefulness
Evaluation:
- REM hypothesis (some evidence, not convincing)
- HLA varient cannot be sole explanation because common in general population
- Hypocretin support from studies of dogs and humans
- Low levels of hypocretin rarely inherited
- Most likely to due brain injury or autoimmune attack
- Link to HLA
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Explanations of Sleep Walking
- Person wakes during SWS but brain arousal incomplete
- Other factors = sleep deprivation, alcohol, hormone changes
- May affect children more because underdeveloped SWS inhibition
Evaluation:
- Evidence for genetic basis
- Diathesis-stress model
- Sleep deprivation triggers sleep walking in vulnerable people
- Psychological cause unlikely because not in REM sleep
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