Biological Rhythms - the Durham School Psychology Department

Report
PSYA3 Revision
BIOLOGICAL
RHYTHMS & SLEEP
Part 1: Biological
Rhythms
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 (‘resynchronise’); 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

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