Syllabus Biological Rhythms Circadian, infradian, and ultradian rhthyms, including the role of endogenous pacemakers and of exogenous zeitgebers in the control of circadian rhythms Disruption of biological rhythms, for example shift work, jet lag Sleep The nature of sleep including stages of sleep and lifespan changes in sleep Functions of sleep, including evolutionary and restoration explanations Disorders of Sleep Explanations for sleep disorders, including insomnia, sleep walking and narcolepsy
Types of Biological Rhythm MUST BE ABLE TO – Identify the three types of biological rhythm (Infradian, Circadian, Ultradian) – Give an EXAMPLE of each – Say how they are different in relation to the length of rhythm SHOULD BE ABLE TO – Explain at least two endogenous pacemakers / exogenous zeitgebers which influence each biological rhythm TOP LEVEL – Link ONE study to each rhythm
Types of Bio Rhythm ULTRADIAN – Cycles of activity which last less than 24hours (i.e. they repeat multiple times in a 24h period) – E.g. STAGES OF SLEEP – Controlled by EPs including the HYPOTHALAMUS and RETICULAR ACTIVATING SYSTEM but may also be influenced by EZs such as noise, light, temp INFRADIAN – Cycles of activity which last more than 24hours – E.g. Menstrual Cycle, Hibernation in animals – Controlled 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) CIRCADIAN – Cycles of activity with a 24h lebgth – E.g. Sleep-wake cycle; body temp – Controlled by EPs such as SCN but influenced by EZs like sunlight levels, temp – Research = RAY/RALPH (Surgical removal of SCN), MICHEL SIFFRE case study – More in the next section
CITCADIAN RHYTHMS and the role of EPs and EZs CIRCADIAN RHYTHMS (CR) = 24h cycles Main example = sleep – wake cycle CRs are CONTROLLED by endogenous pacemakers (EPs; internal biological structures) CRs are INFLUENCED (set) by exogenous zeitgebers (EZs; external factors)
RESEARCH into CRs - role of EZs Initially thought EZs like sunlight control CRs SIFFRE Case study Spent 179 in a cave with no natural light Sleep-wake cycle and body temp was disrupted initially but… … both eventually settled into a regular 25hour pattern This shows that CRs are controlled by EPs but set to a 24hour cycle by EZs such as sunlight
Research into CRs - Role of EPs Recent research suggests CRs are controlled by EPs - internal biological structures such as the Pineal Gland, Melatonin and the SCN RAY Surgically removed the SCN of hamsters who were kept under constant environmental conditions Hamsters sleep-wake cycle was severely disrupted Ray then surgically replaced a new SCN into the hamsters brain from removed from a foetal brain Following this, the hamsters sleep-wake cycle returned to normal This shows that CRs such as the sleep-wake cycle are controlled by EPs, especially the SCN
EVALUATION Research issues – SIFFRE 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 population Ethical way to investigate a potentially dangerous aspect Low ecological validity? – RAY Animal research may not extrapolate to humans due to vast physiological and psych differences. May tell us little about the control of CRs in humans Objective and scientific Ethical Issues?
EVALUATION Must be careful not to make REDUCTIONIST and DETERMINISTIC CONCLUSIONS – All of the research suggests that CRs are largely controlled by EPs but that EZs also play a role in ‘setting’ the CR length – So we must be careful to take into account BOTH aspects when discussing what influences CRs and not simply focus on one IDIOGRAPHIC vs NOMOTHETIC – Everyone’s CRs will be slightly different, with EPs and EZs having different effects on individuals – So we have to be careful not to make over general (nomothetic) conclusions and must instead focus on people individually (idiographic)
DISRUPTION of Bio Rhythms MUST BE ABLE TO – Explain the effects of disruption to biological rhythms – Explain why SHIFT WORK and/or JET LAG causes disruption to bio rhythms – Discuss at least ONE piece of research into disruption of biological rhythms – Explain how the negative effects of disruption can be overcome SHOULD BE ABLE TO – Explain the role of PHASE ADVANCE and PHASE DELAY in the effects of disruption to bio rhythms
What is ‘Disruption’? Disruption to bio rhythms occur when our normal biological rhythms are OUT OF SYNCH with new exogenous factors Known 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
What can cause ‘disruption’? SHIFT WORK – People 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 concentrate – Working 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 APPLICATIONS – Some disasters can be understood as a result of desynchronisation as a result of shift work (e.g. Chernobyl)
Disruption – Shift Work PRACTICAL APPLICATIONS – Research has highlighted that a number of steps can be taken to reduce the negative effects of shift work Provide coffee / other stimulants to keep workers awake High intensity lights which replicate sunlight Increase 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
Disruption – Shift Work KEY STUDY – CZEISLER (Chemical Plant) – Studied workers at a chemical plant in Utah – Noticed that many suffered adverse effects as a result of shift patterns – Imposed 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 increased Evaluation – Generalisation 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?
Disruption – JET LAG Air 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 previously Constant 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)
Disruption – Jet Lag KEY STUDY = RECHT (1995) Baseball teams – Followed a baseball team throughout a season – Found they won more games when travelling West to East – Shows that West to East travel has fewer negative effects and supports the role of phase delay in biological rhythm disruption EVALUATION – Small 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?
Disruption – Jet Lag PRACTICAL APPLICATIONS Research has highlighted that a number of steps can be taken to reduce the negative effects of Jet Lag – Adapt 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
Disruption – General Evaluation Must be careful to take an IDIOGRAPHIC approach as opposed to jumping to NOMOTHETIC, DETERMINISTIC conclusions Although 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