Circadian Rhythms Flashcards
What are biological rhythms?
-distinct patterns of changes in body activity
-conform to cyclical time periods
What are circadian rhythms?
-biological rhythms subject to a 24hr cycle
-regulate a numbat of body processes
What are biological rhythms governed by?
-endogenous pacemakers
-exogenous zeitgebers
What are endogenous pacemakers?
-internal body clocks
What are exogenous zeitgebers?
-external environmental changes
Exogenous zeitbeber as the sleep + wake cycle
-drowsy at night + alert at day
Endogenous pacemakers as the sleep + wake cycle
-superchiasmatic nucleus - provides info from the eye about the light
-a bundle of fibres found in the hypothalamus
-pineal gland - receives the information
-releases melatonin = induces sleep
-adrenal gland - releases cortisol = awake
What was Siffre’s study?
-spent extended periods underground to study effects on biological rhythms
-2 months in the alps
-deprived of exposure to natural light + sound
What were the findings of Siffre’s study?
-length of the sleep/wake cycle was 25 hours
What was similar research to Siffre’s study?
-Aschoff + Wever
-convinced a group of P’s to spend 4 weeks in a bunker
-deprived of natural light
-all but one displayed circadian between 24-25hrs
Conclusions of Siffre’s study
-suggests that the natural sleep/wake cycle is slightly longer than 24hrs
-bu entrained by exogenous zeitgebers
-shouldn’t overestimate influence of endogenous on internal biological clocks
Negatives - there are individual differences in circadian rhythms
-may not always have to conform to cyclical 24 hour periods
-Professor - sleep medicine at Oxford uni
-delayed the starting time of a high school to 10am instead of 8am
-GCSE results went up from 34% of pupils scoring 5 A*-C
-increased from 12% to 42%
-real life example of how circadian rhymes of teenagers aren’t always in line with adults
Negatives - confounding effects of artificial light
-Czeisler - artificial lighting can create shifts in circadian rhythms up to 6 hours
-conducted at a time where researchers believed that artificial lighting had no effect
-the use of light meant that over 2 months -entrained his own circadian through signalling sleeping + waking times
Issues with case studies + small samples
-conducted multiple isolation studies
-may not be able to be generalised to the wilder population
-individual differences in the duration + stages of rhythms
-Aschoff + Wever - large no.of P’s are unlikely to want to participate
-limits the extent to which the findings represent the experiences of the general population
Contradiction - endo + exo both interact
-only is exceptional circumstances are endogenous free running + unaffected by the influence of exogenous
-total isolation (Siffre’s) are rare
-makes very little sense + have low validity to try and separate the 2
-as they interact in real life
