of 16/16
A2 Psychology Unit 3 Bio-Rhythms and Sleep

AQA A2 Psychology Unit 3 - Bio-rhythms and Sleep

  • View

  • Download

Embed Size (px)

Text of AQA A2 Psychology Unit 3 - Bio-rhythms and Sleep

1. A2 Psychology Unit 3 Bio-Rhythms and Sleep 2. Types of Bio-Rhythms Ultradian rhythms More often than once a day Sleep as separated into different stages Circadian rhythms Every 24 hours Sleep/wake cycle, body temperature cycle Infradian rhythms Less often than once a day, more often than once a year Menstrual cycle 3. Sleep/Wake Cycle Controlled by endogenous pacemakers but synchronised by exogenous zeitgebers Siffre Lived in cave for 6 months No human interaction, sound or natural light Researchers measured brain rhythms Called each sleep/wake cycle 1 day Sleep/wake cycle extended to 25 hours Evaluation Sleep/wake cycle controlled internally Proves internal control and external synchronisation Methodological issues Man not woman, case study, no social interaction, we dont live in caves, individual differences, measures biological factors Very good control Wever Reviewed studies of people who spent long periods without exogenous zeitgebers Sleep/wake cycles were 25 hours 4. Menstrual Cycle Good supporting research Reinberg Endogenous zeitgebers Documented menstrual cycle of woman living in cave for 3 months No exogenous zeitgebers Menstrual cycle much shorter, sleep/wake cycle lengthened Exogenous light cues could have effect on Infradian rhythms 5. Control of Sleep/Wake Cycle Main endogenous pacemaker for circadian rhythms is Suprachiasmatic Nucleus (just above the Optic Chiasm) EP Protein Clock 24/25 hr cycle result of protein synthesis Cells of SCN produce protein for number of hours until level stops production and begins to drop When level drops too low, protein produced again Cycle generates bio-rhythm EZ Light and Optic Chiasm SCN able to directly detect light levels as above Optic Chiasm Can then synchronise internal body clock so in sync with day/night cycle 6. Control of Sleep/Wake Cycle Interaction SCN uses both cues to control s/w cycle Via pineal gland Once in 24 hour cycle SCN stimulates pineal gland to remove neurotransmitter serotonin and synthesise to melatonin Makes us sleepy When melatonin gets too high, SCN stops pineal gland As levels drop, we start to wake up Schochat Sleep latency When most likely to fall asleep Sleep gate Where you have enough melatonin to fall asleep About 2 hours before s/w cycle melatonin synthesis 7. Control of Sleep/Wake Cycle Evidence Morgan Removed SCN from hamsters Found they lost circadian rhythms When SCN restored, rhythms restored Miles Man blind since birth had 24.9 hour circadian rhythm EZ did not help (TV, clocks), had to use sedatives Suggests light is dominant EZ Debates Reductionist Lots of research for Melatonin so helped in treatments for insomnia Massively overly-simplistic 8. Disrupting Bio-Rhythms Jet Lag When internal is different to external Phase delay (East to West) Longer day, easier to cope with Delay bedtime Phase advance (West to East) Shorter day, harder to cope with Advance bedtime Evidence Schwartz Results of baseball games Teams travelling from West to East had fewer wins Phase advance caused drop in performance Debates Is impact scientifically supportable Lots of variables that could affect it besides travelling through time zones All correlational No controls Any research looses aspect of natural sleep Is research into treatment scientific Dont really understand many factors involved Cant ask people when unconscious/asleep 9. Disrupting Bio-Rhythms Shift Work Chernobyl and Three Mile Island happened between 1 and 4am Monk and Folkard Rapidly rotating shift work (better) Workers only do couple of shifts before changing to new pattern Slowly rotating shift work (social isolation) Not changed regularly (no more often than every week or month or less often) Cause issues when changing back Lack of daylight, social withdrawal Hawkins Takes individuals about 1 week to change circadian rhythms Rapidly rotating = s/w cycle always out of sync Dawson and Campbell Exposed shift workers to 4 hours very bright light Helped circadian rhythms change quicker Debates Deterministic All people who do shift work will have bad effect Individual differences 10. Nature of Sleep - Stages Stage 1, falling asleep, 15 mins Hypnogogic state Hallucinations (only in stage 1) Myaclonic jerk Brain processing movement when there is none Brainwaves slow from Alpha to irregular Theta Heart rate slows, muscles relax Stage 2, 20 mins 5/10 mins Theta continue to slow Have sleep spindles and K-complexes Heart rate, blood pressure and body temp continue falling Stage 3, 15 mins Theta slow to Delta Fewer spindle and K-complexes Same as stage 2 Stage 4, growth hormone, deepest sleep, 30-40 mins Slowest brainwaves Growth hormone secreted Metabolic rate slowest Very hard to wake up Sleepwalking/talking most likely to occur Stage 5, paradoxical sleep, dreaming sleep, 10-15 mins After quickly going back through stages 3 and 2 Brainwaves rapidly speed up and become irregular and complex Brains oxygen and glucose demands increase Physically least active (paralysed) but brain most active Always tested in lab so artificial with low ecological validity 11. Nature of Sleep Life Span Changes Sleep could be restoration and development of body Infants would need more stage 4 sleep Recover from days of growth and learning Zimbardo Babies spend more time in REM than adults Sleep adaptive Increased chance of survival Less chance of being hunted Health impacts Van Cauter Reduction in stage 4 sleep = drop off in growth hormone after 47 Reduction in muscle mass/ability to exercise Develop tendency to become obese Increase of daytime napping in older adults positively correlated with depression 12. Functions of Sleep Evolutionary Theory Adaptive advantage Prey = to hide Predator = to conserve energy Meddis to remain hidden Prey animals cant see predators at night Staying still (sleeping) could be an advantage Sleep provides prey with time where they are still and less likely to be seen Prey should only sleep at night and predators not at all Not true though Siegel to conserve energy May be adaptive as conserves energy Especially for small/newborn mammals with high metabolism Predators who need to use lots of energy to catch food Doesnt apply to animals like gorillas and lions Evaluation Little or no empirical evidence to support Prey remaining hidden from predators also has worrying anecdotal contradictions Alison and Cicchetti Herd animals spend very little time sleeping Need to eat all the time as vegetation provides very little energy Empson Sleep is universal with animals Even with successful predators who shouldnt have to waste time sleeping Horne Different reasons for different species so universal theory is pointless Debates Evolutionary advantage is being able to sleep in their environment, not sleep itself Vast ideographic differences in how they sleep Overly nomothetic Trying to come up with a theory and apply it universally Need to look more ideographically Only thing you can state nomothetically is that all animals sleep Overly simplistic 13. Functions of Sleep Restoration Theory Allows for physical and mental recovery Oswald NREM restores bodily functions REM restores brain processes Babies spend half time sleeping (18hrs) in REM Double adults Bloch rats in complex mazes Learning complex tasks tire brain using neurochemicals Rats performing complex activities had more REM sleep Jouvet Cats on upturned pots in water Stopped going into REM sleep showed high levels of stress then died No REM = no life so essential to live Evaluation Though REM obviously important, if restoration was only purpose we would expect consistent effects from strenuous activities and sleep deprivation (no consistency) Pilleri River dolphins sleep seconds at a time over 24hrs to avoid debris and drowning Doesnt allow much time for restoration Shapiro Marathon runners didnt need more sleep to recover from their strenuous physical activity Debates Overly simplistic Says we only need sleep to restore Deterministic/overly nomothetic States all animals only sleep to restore Too many exceptions to the rule 14. Sleep Disorders - Insomnia Characterised by Sleep onset latency more than 30mins Time taken to fall asleep Sleep efficiency less than 85% Time in bed actually asleep Several night time awakenings Riemann primary insomnia (explanation) Occurs when no obvious cause Due to largely innate biological mechanisms of sleep Inherited imbalance of body clocks and neural mechanisms could explain it Due to chronic physiological arousal Heart rate and high levels of Cortisol found in people with primary insomnia May be from environment Secondary insomnia (explanation) Clear causes (medical to psychological) of disorder (not seen as true insomnia) Medical Asthma, Parkinsons disease, heart failure Psychological Depression, anxiety, OCD, Posttraumatic Stress Disorder Parasomnias Events that disrupt sleep but not cause daytime sleepiness Restless Leg Syndrome, Sleep Apnoea Lichstein problems diagnosing secondary Hard to diagnose if result of cause of disorder Is depression cause or effect of insomnia Evidence that can go either way Some secondary insomnia with depression could be primary in disguise Problems researching Sleep state misperception Many people claim to have disrupted sleep but actually have normal patterns (suggests mental rather than physical issue) Self help strategies (drugs/alcohol) make sleep harder to achieve, causes learned sleep disorder Makes treatment more complicated (CBT has been used effectively to treat learned sleep disorders) Debates Nomothetic Tries to apply same rule to everyone Hermeneutic Makes assumptions rather than having clear evidence 15. Sleep Disorders - Narcolepsy Characterised by Excessive daytime sleepiness Sufferers fall rapidly into sleep episodes of 10-20mins several times a day Associated with Cataplexy (sudden loss of muscle tone causing collapse even if awake) Co-morbidity Hypnogogic hallucinations (auditory and visual) occur before/after sleep Sleep paralysis occurs on waking for small time period Polysomnography shows sufferers move directly into REM, no NREM Abnormalities in REM control mechanisms (explanation) Sleep paralysis occurs in REM, could explain Cataplexy and paralysis on waking Most dreams occur in REM, could explain hallucinations Potentially hypnogogic state in stage 1 Dont know cause of REM intruding on everyday life Lin - dogs Some pedigree dogs so inbred have greater chance of damage to gene on chromosome 12 Causes reduction in hypocretin which has been correlated with narcolepsy Very loose correlation, no actual link Doesnt show cause and effect Dogs have different chromosomes Overeem humans People with narcolepsy have reduction of hypocretin producing neurons Explanations focus on HLA Complex Gene on chromosome 6 which controls immune system Patients with narcolepsy seem to have mutation in this gene, causes immune system to attack and destroy hypocretin neurons in brain causing abnormalities in REM sleep Evaluation Individual differences Some people with mutation of HLA complex gene dont develop narcolepsy Some sufferers dont have mutation Only 30% concordance rate with MZ twins No treatment available though potential in one involving raising hypocretin levels (closer than insomnia) Debates Deterministic Chromosomes destroyed = narcolepsy, not everyone follows this pattern Nomothetic as trying to explain everyone as the same therefore need to take other factors into account Co-morbidity, environmental, developmental Reductionist Looked in-depth into hypocretin which allows for possible treatments 16. Sleep Disorders Sleep Walking Characterised by Leaving bed while asleep, waking around as if awake Episodes quite short (few seconds to few minutes) Can carry out complex activities and be woken without danger (driving cars) No memory of activities Most common in childhood (30% 5-12yrs have occasional episodes) Explanations Psychodynamic Sleepwalkers acting out dreams But mostly occurs during NREM Dont dream during NREM No evidence for crossover between stage 4 and 5 No evidence for dreaming in stage 4 Hermeneutic interpretation of observed facts Unsupported by families Genetic Sleepwalking runs in families 55% concordance rate in MZ twins (35% in DZ) Suggests genetic Would be 100% if only genetic Need to take other factors into account Brain development (Oliverio) More common in children so could be lack of brain development No direct evidence Adults still sleepwalk Really intelligent person could still sleepwalk Extremely correlational Brain arousal EEGs during sleepwalking have combination of Delta waves (NREM sleep) and Beta waves (aroused waking state) Brain partially asleep, partially awake REM sleep behaviour disorder (RBD) Been responsible for violence, criminal acts, even murder Breedlove Rare cases of sleepwalking where sufferers do act out dreams Should be impossible and undermines understanding Culebras and Moore Could be from damage to Magnocellular Nucleus which normally causes sleep paralysis during REM sleep Legal issues Been used as defence in number of cases Very hard to get judge to accept it Normally family history of extreme sleepwalking required to submit as acceptable defence Debates Polysomnography Nothing causal about it