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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…

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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…

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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…

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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…

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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,…

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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…

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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…

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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…

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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…




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