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biological rhythms: circadian rhythms - Coggle Diagram
biological rhythms: circadian rhythms
biological rhythms
= distinct patterns of changes in body activity that conform to cyclical time periods
influenced by internal body clocks, known as
endogenous pacemakers
also influenced by external changes to the environment, known as
exogenous zeitgebers
types of rhythms
circadian
= last for around 24 hours,
eg sleep/wake cycle
ultradian
= occur many times during the day,
eg stages of sleep
infradian
= take longer than a day to repeat,
eg the menstrual cycle
circannnual
= last over a year, eg
hibernation
circadian rhythms
= a type of biological rhythm
example
= the sleep/wake cycle
governed by 2 factors
daylight (exogenous zeitgeber)
suprachiasmatic nucleus
(scn) (endogenous pacemaker)
scn lies in the hypothalamus just above the optic chasm, which provides info from the eye about light
evaluation
strengths
provides an understanding of the adverse consequences that occur when they're disrupted
for example, research has shown that shift workers are 3x more likely to develop heart disease than people who work typical work patterns
shows that research into the sleep/wake cycle may have real-world economic implications in terms of how to best manage worker health and productivity
used to improve medical treatments
circadian rhythms co-ordinate a number of body processes eg heart rate
the rise and fall of these during a day has led to chronotherapeutics = medical treatment can be administered in a way that corresponds to a persons biological rhythms
eg aspirin taken for heat attack treatment is best taken at night, as they're most likely to occur in the morning
shows circadian rhythm research can help increase the effectiveness of drug treatments
limitations
(counterpoint to shift workers) = studies investigating effects of shift work tend to use correlational methods
means that it's difficult to establish whether desynchronisation of the sleep/wake cycle is actually a cause of negative effects
for example, it has been suggested that high divorce rates in shift workers might be due to the strain of deprived sleep
suggests it may not be biological factors that create the adverse consequences associated with shift work
generalisations difficult to make
studies described are based on small groups of pps & sleep/wake cycles may vary widely from person to person
research found individual differences in sleep cycles between 13 to 65 hours
means that its difficult to use the research data to discuss anything more than averages, which may be meaningless
studies
siffre (1962)
descended into a cave for 2 months and came out in september, but thought it was mid-august
his 'free-running-' didn't conform to a cyclical 24 hour period
demonstrates that after prolonged exposure to a strong exogenous zeitgeber such as light, the sleep-wake cycle becomes disrupted and there is a disconnection between psychological time and the clock
shows the effect of exogenous zeitgebers on circadian rhythms
aschoff & weaver (1976)
55 pps were deprived of light after spending 4 weeks in an underground bunker & found that all of them showed free-running circadian rhythms between 24 & 25 hours
both this and siffre's study suggest that the natural sleep/wake cycle may be slightly longer than 24 hours, but is entrained by exogenous zeitgebers associated with our 24 hour day