Biological Rhythms and Sleep

  • Created by: Kerry
  • Created on: 30-03-15 17:54
What are circadian rhythms? Give 2 examples
Rhythms that last 24 hours, includes the sleep wake cycle and core body temperature
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Outline the sleep wake cycle as a circadian rhythm
Guided by internal clock (EP) and external cues. Internal clock is free running on a cycle of 24-25hrs, external cues help to adjust the internal clock to the environment. External cues include meal times and light
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Outline core body temperature as a circadian rhythm
Lowest at 4am and highest at 6pm, there is a trough after midday which isnt due to eating lunch as occurred in people that hadnt eaten. Practise of siesta is related to the trough
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What are methodological issues of early research?
Early studies investigating free running cycle of internal clock didnt isolate p's from artificial light as thought it didnt affect the CR.
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What did Czeisler et al find related to this?
Altered p's CR down to 22hrs and up to 28hrs using just dim lighting - suggests that it does have an effect
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What did Duffy et al find about the impact of individual differences?
Morning people prefer to go to bed early and wake early, evening people prefer to go to bed late and wake up late. Suggests individual differences in cycle length - results less generalisable and valid
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What is a positive of the biological approach/Miles et al?
Studied blind man, CR couldnt be reset by light. Exposed to various social cues, had little effects on CR. Found it difficult to function in world governed by external cues, suggests EZ's fix external cues
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Negative of this study?
It was a case study - unique person
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What did Folkard et al find?
Read stories to children at 9am or 3pm, 3pm group showed superior recall and cognitive performance - retained 8% more information. Suggests cognitive performance is better when CBT is higher
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What are infradian rhythms? Give examples
Rhythms that last between 24hrs-1 year, examples are the menstrual cycle and SAD
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Outline the menstrual cycle
Regulates ovulation, pituarity gland secretes FSH and LH, stimulates ovary to ripen egg and release oestrogen. When egg is ripe, ruptured follicle secretes progesterone - womb lining prepares for pregnancy. No pregnancy then progesterone reduced
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Outline SAD
Depressive condition, depressed in winter, recover in summer. Pineal gland secretes melatonin and serotonin, more melatonin is secreted when its dark so less serotonin as serotonin is made from melatonin. Low levels of serotonin = depression
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What did Russell et al find about external cues in the menstrual cycle?
Sweat samples collected from 1 group of women and rubbed on upper lip of another group, groups kept separate but menstrual cycles synced with donor. Suggests menstrual cycles affected externally (pheromones) and not just internally (hormones)
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What else could SAD be caused by?
Could be consequence of disrupted CR, as seasons change CR's are disrupted by changing levels of daylight. Means the biological system thinks time is shifting, this is similar to jet lag
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What is a real world application of SAD research?
Led to use of phototherapy, strong lights used in morning and evening to change levels of melatonin and serotonin. SAD sufferers report this treatment relieves symptoms
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What is an ultradian rhythm? Give an example
Rhythms lasting less than 24hrs, the sleep stages are an example
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Outline what happens in stages 1 and 2
Light sleep characterised by changes of activity in the brain, also theta waves with bursts of activity - increased frequency (sleep spindles) and increased amplitude (k complexes)
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Outline what happens in stage 3 and 4
Characterised by slower delta waves, known as slow wave sleep. Is deep sleep where its hard to wake someone, is when most of bodys physiological repair work occurs and important biochemical processes
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What happens in REM?
Characterised by fast desynchronised EEG activity
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What happens throughout the night?
SWS stages get shorter and REM stage gets longer
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What was Dement and Kleitman's study?
Woke p's when brain waves characteristic of REM, found p's highly likely to report dreaming - not all reported dreaming and some reported dreaming outside of REM. Therefore REM isnt dreaming sleep but may help explain why we have dreams
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What is the point of sleep stages?
Sleep stages are part of continuum that occurs with the CR, likely to ensure the biological processes in the body work in unison
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What are EP's?
Internally managed rhythms, common one in mammals is the super chiasmatic nucleus (SCN)
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Outline the SCN
In hypothalamus just above where optic nerves cross over, recieves information about light. SCN divided into ventral (quickly reset by EZ's) and dorsal (less affected by EZ's). SCN sends signals to pineal gland to increase production of melatonin
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What are EZ's?
External cues that can reset the biological clock
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What can light reset?
Dominant EZ that can reset the SCN, resets protein clock as well as protein CRY is light sensitive
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What do Social cues reset? Davidson
EZ for liver and heart cells is meals as the cells are reset by eating
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What was Morgans mutant hamster study?
Bred mutant hamsters that had CR of 20hrs rather than 24hrs, transplanted their SCN into normal hamsters - normal hamsters displayed CR of mutant hamsters
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What was Boivin et al's study?
Used artificial lighting to entrain biological rhythms, could be entrained by dim lighting but bright lighting was more effective
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What does the evolutionary approach/Anton et al suggest about EP's and EZ's?
Endogenously controlled rhythm is adaptive, one adaptive function us that CR allows tight temporal scheduling of physiological and behavioural programmes
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What is jet lag?
The physiological effect of disrupted CR's
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What causes jet lag?
Biological rhythms cant cope with large or sudden changes, dorsal part takes several cycles to adapt. Symptoms include nausea, fatigue, insomnia and loss of appetite
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What is phase advance and phase delay?
Phase advance is west to east - harder to adapt to, phase delay is east to west - easier to adapt to
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What is a consequence of shift work?
Boivin et al found they experience a trough of decreased alertness on shift when cortisol levels are lowest (12-4am). Often sleep deprived as cant sleep during day due to daylight and noise
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What impact does shift work have on health?
Knutsson et al found those who worked shifts for 15yrs were 3x more likely to develop heart disease than non shift workers
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What was Recht et al's study?
Analysed baseball results over 3yrs, E-W teams (phase delay) won a higher % of games, supports that phase delay is easier to adapt to
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Issues with this study?
Not all pro athletes, teams travelling w-e may have had worse players
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What was Solomon's study?
Shift workers experience disruption in social life, hard to meet with friends or spend time with family and divorce rate was higher in shift worker relationships
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What is a real world application of research into shift work? (petrie and herxheimer)
Understanding effects of jet lag/shift work allows us to develop treatments, reviewed 10 studies and found melatonin reduced symptoms when taken near bed time - delayed adaptation if taken at wrong time of day
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What happens in sleep during infancy?
Sleep longest (16hrs) not continuous, dont have REM/SWS but immature versions called active and quiet. CR established after 6 months and the amount of REM/active sleep decreases
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What happens in sleep during childhood?
Similar EEG pattern to adults but sleep more and get more REM sleep. Can experience parasomnia sleep disorders e.g. night terrors
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What happens in sleep during adolescence?
Need for sleep increases, CR change meaning teenagers feel more awake at night and struggle to get up. Males can experience ****** and ***********.
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What happens in adulthood and elderly sleep?
Adults get less sleep and REM, there is increased frequency of sleep disorders like apneoa and insomnia. Elderly find it harder to get to sleep but wake easier/oftenm REM and SWS decrease and may nap to compensate for lack of sleep
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What was Kripke et al's study?
Surveyed (-) 1 million people, 6-7hrs of sleep reduced mortality. 8 hrs increased mortality by 15% and 10hrs+ increased mortality by 30% - too much sleep may be bad
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Negative of this study?
Correlational data
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What was Van Cauter et al's study?
Less SWS means less GH produced, could help explain some of the symptoms associated with old age e.g. reduced bone density and lack of energy
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What does the evolutionary approach suggest about infant sleep?
Babies sleep is adaptive mechanism to make parents lives easier, daytime sleep - parents can get on with chores, night waking - can be fed/wont get cold or hungry. These enhance survival
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What is the role of SWS according to RT?
GH secreted, stimulates growth in children and enables protein synthesis and cell growth in adults. GH is vital in restoration of body tissue as proteins are fragile and constantly need renewing
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What did Sassin et al find?
When sleep wake cycles are reversed by 12 hrs so are GH cycles - GH controlled by neural mechanisms related to SWS
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What else is SWS associated with? Krueger et al
Lack of SWS = reduced immune system functioning, immune system made of antibodies (made of protein)
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What did Siegal suggest about REM?
Amount of REM proportional to immaturity, Platypus is immature at birth and gets 8hrs of REM, dolphin is mature and gets 0 REM sleep
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What role does REM/SWS have in memory?
Stickgold - REM important in consolidation of procedural memory and SWS important in consolidation of semantic and episodic memory
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What was Rechtschaffen et al's study?
Forced rats to remain physically active by rotating a disk they were one everytime they fell asleep, all rats died 33 days later of sleep deprivation
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What was Shapiro et al's study?
Marathon runners slept for 1hr more 2 nights after the race, SWS increased - supports the SWS is associated with physical recovery and the repair of body tissue
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What does the evolutionary approach/Young suggest about sleep?
More we know of sleep patterns the more apparent it is that they are due to environmental pressures, this is key to understanding the role of sleep
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What is the relation of energy conservation to evolutionary theory?
Warm blooded animals expend large amount of energy keeping warm, animals with high metabolic rates use more energy. Sleep is period of enforced inactivity, less energy is used so more can be conserved
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What is the relation of foraging to evolutionary theory?
Sleep is constrained by foraging needs, herbivores spend longer foraging as foods are low in nutrients - means they have less time to sleep
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What is the relation of predation to evolutionary theory?
Sleep is constrained by predation risk, predators sleep longer as prey need to be vigilant to avoid predators so sleep less/when less vulnerable
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What is the relation to waste of time to evolutionary theory?
Meddis suggests sleep allows animals to stay hidden and still when they have nothing better to do at most vulnerable time to predators
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What did Zepelin & Rechtschaffen find?
Animals with higher metabolic rates sleep more than larger animals with slower metabolic rates, supports energy conservations. There were exceptions - sloths large but slept for 20hrs
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What did Allison and Cichetti find?
Species that had a higher predation risk slept less, also found exceptions - rabbits (high danger) slept for as long as moles (low danger)
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What is a negative of the evolutionary approach?
Fails to address key aspects of sleep e.g. why we have such a drive for sleep when sleep deprived, solution may be a combined approach with restoration theory
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What can insomnia be divided into?
Long term/short term and primary/secondary
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Outline primary insomnia
Not directly associated with other health condition or physical cause. May be caused by bad sleep habits, may have had identifiable cause to begin with but this has disappeared. Insomnia persists due to expectations of sleep problems
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What is secondary insomnia?
Has single underlying psychological, medical or environmental cause.
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What are some causes of secondary insomnia?
Environmental factors - caffeine and alcohol delay sleepiness, old age - experience discomfort when they sleep e.g. rheumatism, apneoa - pauses in breathing wake individual 5-30x an hr which disrupts sleep
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Why do we need to distinguish between primary and secondary insomnia?
Implications of treatment - treat cause 1st in secondary but treat insomnia first in primary
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What did Zammit et al find?
Patients with insomnia scored lower on medical outcomes cognitive scale than control p's. They had issues with concentration and problem solving
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What are RWA of insomnia? Arendt et al
Compared driving performance of adults deprived of a nights sleep to those who consumed alcohol. Keeping people awake for 3hrs longer than normal had similar effect on driving performance to moderate levels of alcohol
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What is the REM explanation of narcolepsy?
Symptom is a loss of muscle tone - experienced in REM, experience intrusions of REM type sleep as hallucinations. Narcolepsy caused by malfunction in system that regulates REM
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What is the HLA explanation - Honda et al?
HLA is found on surface of WBC's and coordinate immune responses, narcoleptics have an increased amount of one type of HLA
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What is the hypocretin explanation?
Neurotransmitter that regulates sleep/wakefulness by interacting with systems that control homeostasis and emotions in the hypothalamus. Narcoleptics have a low level of hypocretin
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What was Vogel's study?
Found REM in sleep onset of narcoleptics, REM normally occurs later in sleep cycles. Suggests a malfunction in REM regulatory system
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What was Lin et al's study?
Narcoleptic dogs have a mutation on chromosome 12, mutation disrupted the processing of hypocretin
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What is a RWA of hypocretin explanation?
Narcolepsy caused by hypocretin means cure is obvious - give them hypocretin. Hypocretin is unstable so broken down before it reaches the brain, researchers are trying to create artificial version
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What causes sleep walking?
Sleep walkers are in deep sleep so are hard to wake, their EEG patterns are characteristic of SWS and wakefulness. Sleep walking caused by incomplete arousal
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What are risk factors for sleep walking?
Childhood (get more SWS when SW occurs), sleep deprivation and alcohol. This only triggers SW in some people suggesting a inherited genetic vulnerability for SW
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What did Zadra et al find?
40 patients referred to sleep lab for sleepwalking, prevented from falling asleep. 50% SW on first night and 90% on 2nd night. Normal people dont sleepwalk when deprived of sleep - acts as stressor in vulnerable individuals (diathesis stress model)
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Card 2


Outline the sleep wake cycle as a circadian rhythm


Guided by internal clock (EP) and external cues. Internal clock is free running on a cycle of 24-25hrs, external cues help to adjust the internal clock to the environment. External cues include meal times and light

Card 3


Outline core body temperature as a circadian rhythm


Preview of the front of card 3

Card 4


What are methodological issues of early research?


Preview of the front of card 4

Card 5


What did Czeisler et al find related to this?


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