Sleep - Bio Rhythms

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  • SLEEP -Biological Rhythms
    • Circadian Rhythms - 24 hrs
      • SLEEP WAKE CYCE - controlled by SCN, governed by internal endogenous clock which maintains free running cycle in absence of external cues.
        • SIFFRE - long periods underground - cave, internal clock generally adjusted to 24 hrs, did overrun, 48 hrs. SUPPORT of endogenous clock, without external cues light. CASE STUDY, LACKS GEN
      • SLEEP-WAKE CYCLE can be entrained to some extent, by external cues.
        • INDIVIDUAL DIFFERENCES - cycle length varies from  13 hrs to 65 hrs. Cziesler et al. MORNING TYPES, EVENING TYPES - Duffy et al
        • EXPLAINS BETTER IQ TEST RESULTS at 7pm compared to 9am (Gupta) - effect on cognitive performance
        • Not clear, CAUSE OR CORRELATION. Research, deliberately lowered body temp, lower cog performance but unclear whether high core body temp increased physiological arousal which creates effect. (Wright et al)
      • HORMONES - CORTISOL LOWEST AT MIDNIGHT, PEAK AT 6AM. creates ALERTNESS. explains cant think clearly, wake up earlier than normal
        • explanations suggest SLEEP-WAKE patterns FIXED caused by internal mechanisms and external cues. LEAD TO CHRONOPHAR-MACOLOGY. RWA. study of how timing affects drug treatments. E.g. drugs that act on hormones may have no effect when target hormone levels are low.
        • H/E FLEXABILITY IN SYSTEM - go to bed later, wake up later. FOLKARD ET AL, pp managed to keep to 22 hr clock.
    • Ultradian Rhythms - Less than 1 day
      • SLEEP STAGES - 1&2; alpha, HR slows, temp drops. 3&4; SWS, delta, MR slows, growth hormone produces. REM; paradoxical state, associated with dreaming, EEG similar to when awake
        • INDIVIDUAL DIFFERENCES - babies, quiet & active sleep - immature versions. Old - lower bone density related to lack of SWS lack of growth hormone.
        • LINK BETWEEN REM & DREAMING QUESTIONED - Dement and Kleitman, woke people during REM, found dreaming but not exclusive to rem. Other stages. Questions reliability of explanation, contradictory findings.
      • BASIC REST-ACTIVITY CYCLE; KLEITMAN - during day, 90 min period rest followed by activity.
        • BRAC HAS HIGH VALUE - ensures BIO PROCESSES WORK IN UNISON - complex metabolic processes in different parts of body at same time - coordination advantageous.
        • SUPPORT FREIDMAN AND FISHER observed psychiatric patients over a 6 hour period, notices clear 90 minute patterns between eating and drinking episodes.
    • Infradian Rhythms - MORE than 1 day
      • Monthly - MENSTRUAL CYCLE; controlled by fluctuating levels of hormones that regulate ovulation. Pituitary gland produces FSH and LH which stimulate production of oestrogen and later progesterone that build up lining of womb for fertilsed egg. No fertilization - prog lvls fall, lining shed.
        • CAN BE ENTRAINED EXOGENOUSLY - PHEROMONES can entrain MC (rubbing other womens sweat on upper lip). Russel et al. Bio rythms can be entrained exogenously such as infrandian.
        • CAN HAVE -VE EFFECTS - PMS, direct effects - anxiety, depression, mood swings. Biological cause - Dalton, PMS led indirectly to lower academic achievement, suicide & crime
      • SEASONAL AFFECTIVE DISORDER - yearly, depressed in winter, recover in summer. More melatonin in winter, darker -> less serotonin -> depression.
        • ALTERNATIVE EXPLANATION - may be due to DISRUPTED CIRC RHYTHM - due to going to bed earlier as darker earlier in winter, - puts rhythms out of phase.
        • RWA - development of PHOTOTHERAPY, exposes sufferers to very strong light (6000-10000 Lux). H/e may be due to Placebo effect, Eastman et al - 32% improved with placebo alone.
    • Endogenous Pacemakers
      • SCN - cluster of nerve cells in hypothalamus. Recieves info about light as located above Optic Chiasma where nerves from each eye cross over. One scn in each hemisphere, ventral - easily reset by external cues. Dorsal - less affected by light (Albus et al.)
        • EFFECT OF SCN SUPPORTED BY MORGAN - demonstrated using 'mutant' hamsters bred with 20 hour circadian rhythms. SCN transplanted into 'normal hamsters' - exhibited mutant rhythm.
          • ETHICAL ISSUES - ANIMAL STUDY - animals permanently harmed. Generalisations may not be justified, lacks valid - bio systems different
      • PiNEAL GLAND receives signals from SCN about light - produces melatonin - induces sleep - darkness - more melatonin.
        • Adaptive nature of bio rhythm - EVOLUTIONARY APPROACH - chipmunks without functioning SCNs found more likely to die - awake at night making noise - attract predators - DeCoursey et al
        • SCN can explain effects of jet lag - ventral and dorsal portions out of phase. - desynchronisation - FOLKARD effects of isolation, women, cave, temp and sleep rhythms became different - experienced symptoms similar to jet lag.
    • Exogenous Zeitgebers
      • LIGHT - effects SCN and other peripheral oscillators - contain cryptochrome (CRY) substance sensitive to light. Campbell & Murphey reset circadian rhythms by shining light on backs of knees.
        • ARTIFICIAL LIGHTING ENOUGH - early studies of bio rhythms exposed pp's to artificial lighting and assumed not bright enough to entrain rhythms. BOIVIN ET AL - does have effect, h/e bright lighting is better at resetting circadian rhythms.
        • RWA - living in artificial lit world, DISRUPT MELATONIN production, increased incidence of cancer. (STEVENS).
      • SOCIAL CUES & TEMP - social conventions, mealtimes (Davidson) reset heart and liver cells. Cold signals for reduced activity.
        • HAVING BIO GOVERNED SYSTEM HAS ADVANTAGES H/W GOES WRONG, DIFFICULT TO OVERRIDE. e.g physiological changes during adolescence can cause delayed sleep phase syndrome, leading to unusual sleep patterns.Exog does entrain h/e not sig.
        • ADVANTAGES TO BLENDED SYSTEM - enog and exog work as 1 system. both cues interact and enable internal synchronization of physiological processes and external synchornisation of inevitable environmental changes.
    • Disruption of Biological Rhythms
      • SHIFT WORK
        • EFFECTS ON HEALTH - KNUTTSEN ET AL - 3x more likely to develop heart disease. ALERTNESS DECREASES - cortisol levels lowest at midnight (boivin et al)
          • SOCIETY RELIES ON SHIFT WORK - effects should be understood and try to reduce -ve effects. Major disastors (e.g. Exon Valdez) blamed on errors arising from disruption of bio rhythms assosicated with shift work RWA.
          • BOIVIN et al body temp lowest middle of night - working in circadian trough - negative effects. Helped by bright lighting to keep more alert help promote circadian adaption - Boivin and James studies nurses at work.
        • SLEEP DEPRIVATION inevitable. Distubances in day - noise, light etc. Length, 2 hrs less than av. Tilley & Wilkinson
          • RWA - Research found systems with fewer -ve effects - non-fluctuating sifts are better. e.g, weeks of working days, followed by week of nights (Gold et al)
          • SHIFT WORK EFFECTS NOT JUST DUE TO DISRUPTION OF RHYTHMS BUT INDIRECTLY to things associated with SOCIAL DEPRIVATION and FAMILY DISRUPTION. SOLOMON - divorce rates high as 60% in shift workers
  • SIFFRE - long periods underground - cave, internal clock generally adjusted to 24 hrs, did overrun, 48 hrs. SUPPORT of endogenous clock, without external cues light. CASE STUDY, LACKS GEN


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