Biological Rhythms Flashcards
What is a biological rhythm
Distinct patterns of changes in body activity that conform to cyclical time periods, influenced by internal body clocks (endogenous pacemakers) and external changes to the environ (exogenous zeitgebers)
What is a circadian rhythms
Type of biological rhythm subject to a 24 hour cycle which regulates a number of body processes eg sleep/wake cycle and changes in core body temp
Explain Siffre’s cave study
-spent several extended periods underground to study effects on his own biological rhythms
-resurfaced in September after two months believing it to be august
-biological rhythm settled down to one just beyond usual 24hrs of 25 hrs though he did continue to fall asleep and wake up on a regular schedule
Expand on Aschoff’s study
-ppts spent four weeks in WW2 bunker deprived of natural light
-all but one ppt displayed a circadian rhythm between 24-25hrs, suggesting natural sleep/wake cycle may be slightly longer than 24hrs but that it is entrained by exogenous zeitgebers associated with our 24hr day eg number of daylight hours/ typical meal times
Expand on Folkard’s study
-studied group of 12 ppts who lived in dark cave for 3 weeks going to bed when clock said 11:45pm and rising when it said 7:45am
-over course of the study researchers gradually speeded up clock (unknown to ppts) so an apparent 24 hr day only lasted 22 hours
-only one of the ppts able to comfortably adjust to new regime
-suggests existence of strong free-running circadian rhythm that cannot easily be overridden by changes in external environ
Expand on strength that practical application to shift work
-shift work found to lead to desynchronisation of circadian rhythms= can lead to adverse cognitive and physiological effects
-research shown Night Shift workers suffer concentration lapse at 6am which increases likelihood of accidents, also 3x more likely to suffer from heart disease as result of adjusting to sleep/wake cycles
-economic implications in terms of maintaining worker productivity and preventing accidents in the workplace
Expand on strength that there is application to pharmacokinetics
-by understanding impact on our health of circadian rhythms it can help determine the best time to administer drug treatments
-eg risk of heart attack greatest in early morning so drugs can be taken at night but not released until when they will be most effective
-there are peak times for administration and dosage of a variety of drugs that treat a range of disorders eg cancer that increase their efficacy
Expand on strength that there is support from the cave study
-Siffre spent two months in the caves of the southern Alps deprived of light and sound, determining that his circadian rhythm remained between 24-25hrs
-further research support by Aschoff found that sleep/wake cycle lasted just under 25hrs concluding that exogenous zeitgebers may have an impact mediating the cycle
-suggests the body’s internal clock is set to 24-25hrs in the absence of external cues and is intolerant to any major alterations to sleep and wake cycles (eg shift work/jet lag)
Expand on limitation that there are issues with case study evidence
-Siffre study was only on one individual and Folkard and Aschoff studies only on a handful of people
-consequently it is not possible to generalise these results to whole populations of people as there may be individuals difs in the research sample that makes these ppts respond to the changes in sleep/wake cycle in atypical ways eg Siffre found when he went into the cave at 60yo his body responded very differently with his body clock following more of a 48hr cycle
-suggests results cannot be generalised from these small samples to wider pop as factors such as age and gender may have significant impacts on our circadian rhythms
Expand on limitation that there is poor control in studies
-in the cave studies the exposure to artificial light eg torches/phones was not controlled
-it was assumed it was only natural light that has an influence on our bio rhythms however research has found that dim artificial lighting can adjust the circadian rhythm between 22-28hrs
-means the results to the og study may lack validity and the sleep wake cycle may vary considerably more
H: impact of artificial lighting on our circadian rhythms also has practical implications when it comes to use of electronic devices eg smartphones during dif times of the day
