Presentation on theme: "PSYA3 Revision BIOLOGICAL RHYTHMS & SLEEP Part 1: Biological Rhythms"— Presentation transcript:
1PSYA3 Revision BIOLOGICAL RHYTHMS & SLEEP Part 1: Biological Rhythms
2Syllabus Biological Rhythms Sleep Disorders of Sleep • Circadian, infradian, and ultradian rhthyms, including the role of endogenouspacemakers and of exogenous zeitgebers in the control of circadian rhythms• Disruption of biological rhythms, for example shift work, jet lagSleep• The nature of sleep including stages of sleep and lifespan changes in sleep• Functions of sleep, including evolutionary and restoration explanationsDisorders of Sleep• Explanations for sleep disorders, including insomnia, sleep walking andnarcolepsy
3Types of Biological Rhythm MUST BE ABLE TOIdentify the three types of biological rhythm (Infradian, Circadian, Ultradian)Give an EXAMPLE of eachSay how they are different in relation to the length of rhythmSHOULD BE ABLE TOExplain at least two endogenous pacemakers / exogenous zeitgebers which influence each biological rhythmTOP LEVELLink ONE study to each rhythm
4Types of Bio Rhythm ULTRADIAN INFRADIAN CIRCADIAN Cycles of activity which last less than 24hours (i.e. they repeat multiple times in a 24h period)E.g. STAGES OF SLEEPControlled by EPs including the HYPOTHALAMUS and RETICULAR ACTIVATING SYSTEM but may also be influenced by EZs such as noise, light, tempINFRADIANCycles of activity which last more than 24hoursE.g. Menstrual Cycle, Hibernation in animalsControlled by EPs including HYPOTHALAMUS, PITUITARY GLAND and influenced by EZs such as light and PHEROMONES in the environment (note the RUSSELL, 1980, study into synchronizing menstrual cycles)CIRCADIANCycles of activity with a 24h lebgthE.g. Sleep-wake cycle; body tempControlled by EPs such as SCN but influenced by EZs like sunlight levels, tempResearch = RAY/RALPH (Surgical removal of SCN), MICHEL SIFFRE case studyMore in the next section
5CITCADIAN RHYTHMS and the role of EPs and EZs CIRCADIAN RHYTHMS (CR) = 24h cyclesMain example = sleep – wake cycleCRs are CONTROLLED by endogenous pacemakers (EPs; internal biological structures)CRs are INFLUENCED (set) by exogenous zeitgebers (EZs; external factors)
6RESEARCH into CRs - role of EZs Initially thought EZs like sunlight control CRsSIFFRECase studySpent 179 in a cave with no natural lightSleep-wake cycle and body temp was disrupted initially but…… both eventually settled into a regular 25hour patternThis shows that CRs are controlled by EPs but set to a 24hour cycle by EZs such as sunlight
7Research into CRs - Role of EPs Recent research suggests CRs are controlled by EPs - internal biological structures such as the Pineal Gland, Melatonin and the SCNRAYSurgically removed the SCN of hamsters who were kept under constant environmental conditionsHamsters sleep-wake cycle was severely disruptedRay then surgically replaced a new SCN into the hamsters brain from removed from a foetal brainFollowing this, the hamsters sleep-wake cycle returned to normalThis shows that CRs such as the sleep-wake cycle are controlled by EPs, especially the SCN
8EVALUATION Research issues SIFFRE RAY Case study – generalisation issues. Other people may be affected differently by the situation so the study may tell us little about what controls CRs in the general populationEthical way to investigate a potentially dangerous aspectLow ecological validity?RAYAnimal research may not extrapolate to humans due to vast physiological and psych differences. May tell us little about the control of CRs in humansObjective and scientificEthical Issues?
9EVALUATIONMust be careful not to make REDUCTIONIST and DETERMINISTIC CONCLUSIONSAll of the research suggests that CRs are largely controlled by EPs but that EZs also play a role in ‘setting’ the CR lengthSo we must be careful to take into account BOTH aspects when discussing what influences CRs and not simply focus on oneIDIOGRAPHIC vs NOMOTHETICEveryone’s CRs will be slightly different, with EPs and EZs having different effects on individualsSo we have to be careful not to make over general (nomothetic) conclusions and must instead focus on people individually (idiographic)
10DISRUPTION of Bio Rhythms MUST BE ABLE TOExplain the effects of disruption to biological rhythmsExplain why SHIFT WORK and/or JET LAG causes disruption to bio rhythmsDiscuss at least ONE piece of research into disruption of biological rhythmsExplain how the negative effects of disruption can be overcomeSHOULD BE ABLE TOExplain the role of PHASE ADVANCE and PHASE DELAY in the effects of disruption to bio rhythms
11What is ‘Disruption’?Disruption to bio rhythms occur when our normal biological rhythms are OUT OF SYNCH with new exogenous factorsKnown as ‘desynchronisation’It takes the body a period of time to adapt (‘re-synchronise’); during this time there may be negative consequences such as fatigue, insomnia, depression, aggression and cognitive problems such as an inability to concentrate (which may lead to accidents)Constant disruption may also have more serious effects, such as an increased risk of cancer or other illness as disruption reduces the effectiveness of the immune system
12What can cause ‘disruption’? SHIFT WORKPeople who work ‘shifts’ are constantly disrupting their biological rhythms (i.e. working when their body expects to be asleep)Can lead to fatigue, depression and an inability to concentrateWorking nights may cause additional problems as here a person is trying to sleep when it is the most difficult to do so (i.e. when light levels are high, when there is a lot of activities going on).THEORETICAL APPLICATIONSSome disasters can be understood as a result of desynchronisation as a result of shift work (e.g. Chernobyl)
13Disruption – Shift Work PRACTICAL APPLICATIONSResearch has highlighted that a number of steps can be taken to reduce the negative effects of shift workProvide coffee / other stimulants to keep workers awakeHigh intensity lights which replicate sunlightIncrease time on a particular shift to allow for resynchronisation (ideally have people on permanent shifts)Forward Shift pattern as opposed to backwards as this is easier to cope with as it requires PHASE DELAY as opposed to PHASE ADVANCE
14Disruption – Shift Work KEY STUDY – CZEISLER (Chemical Plant)Studied workers at a chemical plant in UtahNoticed that many suffered adverse effects as a result of shift patternsImposed a forward shift rotation (phase delay) as opposed to backwards (phase advance)Found that many workers reported fewer problems when tested subsequently and also that productivity increasedEvaluationGeneralisation issues – only a small number of workers studied; will everyone respond in the same way?Operstionalisation of improvement – how was this defined? Possibility of subjectivity / bias?
15Disruption – JET LAGAir travel across time zones leads to rapid desynchronisation of Bio Rhythms (e.g. the SCN is telling the body to sleep when actually it is the middle of the day in the new time zone!)Can lead to ‘Jet Lag’ which includes psychological and physiological problems such as those outlined previouslyConstant disruption can have long term serious effects (e.g. RAFNSSON, 2001, female flight attendants have DOUBLE the risk of breast cancer)Research suggests that the number of time zones crossed influence the level of disruption (1 day to adjust to 1 hour difference)Also the DIRECTION OF TRAVEL is key (East to West travel is easier to cope with as it requires PHASE DELAY; West to East requires PHASE ADVANCE so is harder to cope with and leads to more negative effects)
16Disruption – Jet Lag KEY STUDY = RECHT (1995) Baseball teams Followed a baseball team throughout a seasonFound they won more games when travelling West to EastShows that West to East travel has fewer negative effects and supports the role of phase delay in biological rhythm disruptionEVALUATIONSmall Sample; generalisation issues – will everyone respond to the disruption / direction of travel in the same way?Operatonalisation of negative effects; judged purely on whether the team won or lost – what about other measures / effects?
17Disruption – Jet Lag PRACTICAL APPLICATIONS Research has highlighted that a number of steps can be taken to reduce the negative effects of Jet LagAdapt to the new time zone before travel (e.g. eating, sleeping patterns)Take Melatonin tablets to help a person sleep when it is appropriate for the new environment
18Disruption – General Evaluation Must be careful to take an IDIOGRAPHIC approach as opposed to jumping to NOMOTHETIC, DETERMINISTIC conclusionsAlthough many people are effected by shift work / jet lag, some individuals are not.We must be careful not to make overly general (nomothetic) conclusions as everyone is different and everyone’s biological responses will be slightly different