Biological Rhythms and Sleep Revision Notes

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Biological Rhythms
Disrupting Biological Rhythms
Jet Lag
Occurs when individual crosses time zones, discrepancy between internal time (body clock) and
external time (local zeitgebers e.g. light, meal, work times), symptoms include fatigue, headaches,
insomnia, irritability and depression.
Phase delay: East to West, day is lengthened, delay sleep time to adjust, EASIER
Phase advance: West to East, day is shorter, advance body clocks to catch up with local time
Recht ­ US baseball results, over 3 years, team East West won 44%, West East won 37%
o Travelling east more difficult due to phase advance, performance effected
o A03
Real life ­ not artificial lab experiment higher ecological validity however
extraneous variables...
Reduce negative consequences
o Melatonin ­ Herxheimer and Petrie, 10 studies, melatonin taken before bedtime
remarkably effective HOWEVER taken at wrong time can delay adaptation
o Social customs ­ can help entrain biological rhythms. E.g. when travelling, eat at right time
and go sleep when clock says to go sleep. Fuller ­ period of fasting followed by eating on
new time schedule
o Bright lights ­ Gronfier et al ­ entrain circadian rhythms to > 24 hrs using modulated light
exposure (MLE)
o A03
Individual differences ­ some people more affected by circadian disruption than
others ­ Reinberg et al ­ people whose circadian rhythms adapt more slowly
actually cope best with jet lag/shift work
Shift Work
Individual working when body wants to be asleep vice versa, consequences include depression,
fatigue, anxiety BUT body can reprogram bio.rhythm cope with shift work
Real world applications & importance of understanding consequences to prevent disasters
o Accidents such as chemical explosion at Chernobyl ­ between 1AM and 4AM
o Explained by errors made when bio.rhythms associated with shift work disrupted
Boivin - alertness decreases when cortisol levels are lower in middle of night, when core body
temperature also lowest (circadian trough)
o A03
Gender bias ­ only males used unrepresentative
Verify lab experiments ­ need to be confirmed by natural studies, Boivin&James
studied nurses at work and found exposure to bright lights promoted circadian
adaptation supported lab findings
Knutsson ­ individuals who worked shifts for > 15yrs were 3x more likely to develop heart disease
than non-shift workers
Martino et al ­ linked shift work to organ diseases(kidney) may be due to direct effects of
desynchronisation or indirect effects such as social deprivation and family disruptions e.g. divorce
rates may be as high as 60% in shift workers
IDA ­ Reducing harmful effects of shift work
Changing shift patterns ­ Gold et al: Rotating shifts: non-fluctuating shifts are better because body
can get used to sleep wake pattern i.e. week of working days, week of nights. Bambra et al:
Forward-rotating shifts: (phase delay) better than backward-rotating shifts
Artificial lighting ­ Boivin ­ showed very bright lighting can reset bio.clock, found that dim lighting
actually had opposite effect and didn't reset the rhythm. suggests that in workplace lighting
should be bright
Lifespan Changes in Sleep

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Biological Rhythms
From infancy to old age there're major changes in amount + kind of sleep experienced
Babies need significant amount more of sleep than children and adults, and also have different
sleep patterns and stages of sleep
Infants usually sleep approx 17hrs a night with about 50% in REM sleep sleep not continuous as
they are interrupted every 3-4 hours for feeding
By age of 6 months circadian rhythms is established, by age of 5 children have similar
electroencephalograph (EEG) patterns to adults…read more

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Biological Rhythms
Initial insomnia (trouble falling asleep), middle insomnia (trouble remaining sleep), terminal
insomnia (waking up too early)
Classified as transient (short term), intermittent (occasional) and long term (month+)
Primary ­ insomnia occurs on its own, with no known cause, for more than a month
Secondary ­ underlying cause and insomnia is only symptom of main disorder e.g.…read more

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Biological Rhythms
Sleep walking (somnambulism)
Terms that covers any activity that takes place during sleep but more common while walking
More common in childhood affecting 20% of children
Only occurs during NREM sleep/SWS sleep walker not conscious of activity
EEG recordings during sleep walking show delta waves (typical of SWS) + beta waves (typical of
awake state) person in SWS is awakened but arousal is incomplete incomplete arousal may be
Sleep walking increased by sleep deprivation, fever, stress, alcohol and psychiatric conditions
o…read more

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Biological Rhythms
Circadian Rhythms
Sleep-Wake Cycle
Siffre: looked at what happens when internal clock is `free-running' ­ free from external cues
spent 7 months underground lacking natural light
o Results: eventually settled into a 25hr cycle of sleep + activity
o Pattern of sleep exists even without external cues, however is slightly than 24hr cycle
Despite lack of exogenous zeitgebers, endogenous pacemaker still ran at 25hr
Only one man findings cannot be generalised lack validity
o Individual differences in circadian cycle length…read more

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Biological Rhythms
Infradian Rhythms
Monthly Cycle
Human menstrual cycle is driven by fluctuating hormone levels to regulate ovulation
Pituitary gland releases hormones (FSH and LH) which stimulate a follicle in an ovary to ripen an egg
and release oestrogen
Lining of womb prepares for pregnancy by increasing blood supply
If no pregnancy occurs, after 2 weeks the lining of the womb sheds (female has period)
o Shows that this is an endogenous pacemaker
Menstrual cycle may be governed by exogenous factors (other than…read more

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Biological Rhythms
Ultradian Rhythms
Sleep Stages
Stage 1 + 2: relaxed state, easily woken, alpha and theta waves, heart rate slows, temperature
Stage 3 +4: SWS, delta waves, metabolic rate slowest, growth hormone produced
Stage 5: REM, `paradoxical sleep' (eyes active but body paralysed), dreaming
o Once cycle takes about 90mins
Dement & Kleitman ­ monitored EEG records during sleep ppts woken at different stages of sleep
o Results: ppts woken during REM sleep reported dreams 80-90% of time in great detail…read more

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Biological Rhythms
Endogenous Pacemakers
Internal biological clocks suprachiasmatic nucleus (SCN) located in hypothalamus regulates
all internal clocks when light hits retina, SCN sends electrochemical signal to pineal gland when
info from SCN indicates external light levels are low secretes melatonin less light = more
melatonin, makes person sleepy by inhibiting brain mechanisms that promote wakefulness
Support: DeCoursey ­ lesions in brains of 24 chipmunks to remove SCN returned to habitat
without SCN to regulate sleep-wake cycle after 80 days, significantly more of surgical…read more

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Biological Rhythms
Determinism: bio rhythms are to some degree determined by internal/external forces rather than an
individual's will to do something e.g. need for sleep narcolepsy shows some effects of not having enough
sleep (body shutting down) + research on animals shown lack of sleep can result in death however
element of free will as to how much we can control some of own biological rhythms. E.g.…read more



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