Sleep and Biological Rhythms revision

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Biological Rhythms & Sleep

Biological Rhythms

Circadian rhythm – within 24 hours

Circadian rhythm is controlled by the EP: SCN (damage in rats found circadian rhythm patterns eliminated) and EZs, predominantly light

Sleep / Waking

  • Siffre - 6 months in cave w/ few external cues made body clock change to 25-30 hours w/ 48 hours in once case + as he got older his body clock ticked slower
  • Folkard –Aimed to see if EZs could override the circadian rhythm. In a cave away from EZs w/ agreed sleep wake times. When clocks changed 2 hours quicker, only 1 pp changed their cycle to 22 hours, rest had free running rhythms. Only took a few days to resynch (importance of EZs in resynching)
  • Aschoff– In a WW II without EZs pps followed a cycle of 25 hours where they could change artificial light but was idiosyncratic 21-29        
  • Evidence from disrupting rhythms shows EZs have limited control

Evaluation

  • Individual differences - shown in all studies + Siffre idiosyncratic + morning vs. night people + circadian length + lifespan differences (also Siffre)
  • Application in chronotherapeuatics
  • Shows EZs have some control, but it’s minimal and better viewed as interaction
  • Unlikely why we have evolved with 25 hour clock compared to 24 (Czeisler – body clock is 24 hours in highly controlled experiment)
  • Methodological – effects of artificial light + allowing pps to turn lights on and off gave control to reset internal clock (research shows it does affect = application in everyday use)
  • Miles – man had circadian rhythm of 24.9 hours, needed drugs to keep up with real world – evidence for genetically pre-determined & EZs limited control + biological approach being right to be deterministic

Temperature

  • Fluctuates w/ lowest at 4am and highest at 6pm
  • Cognitive performance correlated w/ temperature, where LTM recall is highest when temperature is
  • Folkard – 12-13 year olds followed this correlation w/ highest recall in afternoon vs. morning
  • Tests in cold water lower IQ
  • rough at midday which is reflected in siesta (sleep interaction)

Evaluation

  • Alertness is highest when temperature is lowest
  • Field study found no such correlation

Infradian Rhythms – more than 24 hours

SAD

  • Depression rates higher in winter months
  • Unsure cause, best attempt due to lack of light = imbalance melatonin which interferes with neurochemicals causing depression
  • Was suggested that artificial light could reverse these effects by manipulating circadian sleep / wake cycle
  • Pps with SAD received 30 min exposure to bright light improved 5% vs. ion placebo

Evaluation

  • Application for practical treatment = phototherapy
  • Light is a small factor, multicausal problem
  • Biorhythms can go wrong
  • Could be affect of circadian disruption due to natural time shift of the seasons

Menstrual Cycle

Endogenous pacemakers

  • Controlled endogenously by hormones produced by the pituitary gland every 28 days as part of the endocrine system
  • Interaction between rhythms - affected by circadian rhythms since secretion of hormone occurs in the morning + affected by jet lag & shift work

Exogenous zeitgebers

  • EZs include light (links w/ circadian control): cycle of women in cave was shortened
  • McClintock –Pheromones acted as exogenous zeitgebers for synchronised periods

Evaluation

  • Evolutionary – but what function? + Side effects make it doubtful.
  • Purpose of the cycle is to conserve energy – better to restrict fertility therefore needs to have exogenous zeitgebers
  • Research showed no synch in basketball team
  • Methodological problems – small sample, rely on pps recollection. Wilson – once this is taken into consideration evidence for synch evaporates
  • Deterministic e.g. used in law

Circa-annual Rhythms

Research on both showed that changing environment didn’t affect endogenous body clock

Migration -Kept birds caged. Despite lack of external stimuli, still showed signs of migration restlessness. Therefore, endogenous control

Hibernation -Control on squirrels exposure to light & temperature – still had natural pattern

Ultradian Rhythms - less than 24

Sleep Stages

  • During a night’s sleep you pass through different sleep cycles of 90 mins
  • REM entails vivid dreams, similar EEG to awake. NREM spit into 4 stages which are identifiable by EEG patterns w/ their different depth of waves + growth hormone SWS
  • Most complete 5 ultradian cycle w/ progressively less SWS & more REM towards morning
  • Difference in stages is not just oscillations of depth but qualitatively different
  • Reticular formation, locus coeruleus & raphe nuclei control REM / NREM (links w/ affective disorders & sleep)
  • Dement –found dreaming in both NREM & REM by waking up and asking for subjective recall. Found REM dreaming was vivid, and used to explain high brain activity in REM

EZs & EP control

  • Ultradian rhythm of NREM/REM depends upon endogenous pacemakers e.g. age in lifespan
  • Locus Coeruleus (cells in pons) activate REM along with raphe nucleus
  • EZs like alcohol can disrupt cycle

Evaluation

  • Objective evidence – EEG, EOG & EMG provide objective measures of sleep
  • Artificiality of sleep laboratory – lacks mundane realism, generability & ecological validity
  • Universality of sleep stages

Basic Rest Activity Cycle (BRAC)

  • Verbal & spatial performance had a 96 minute cycle
  • Psych patients recorded to have 90 minute rhythm of eating / drinking
  • Ultradian cycle has to be controlled by a different biological clock than the one governing circadian rhythm. If that is destroyed the 90min cycle still continues

Control of Biological Rhythms

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Endogenous pacemakers

Many cycles follow 24-hour cycle while free running, follows that there must be internal clock (Some genetic - Miles)

Supreachisatic Nucleus

  • The main EP is the SCN which generates a circadian rhythm acting as an internal clock keeping to sleep/wake cycle
  • It is the product of evolution and largely genetic (Miles)

SCN (cells in hypothalamus above optic chiasm which reacts to light – influences 24 hour cycle)  regulates pineal gland melatonin secretion = sleep induced

Morning = CLOCK + CYCLE which creates PERIOD + TIME  CC reduced, and in turn PT. ...

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