circadian rhythms Flashcards
biological rhythms
influence how our body systems behave
governed by internal clocks called endogenous pacemakers or external factors called exogenous zietgebers
what is a circadian rhythms
last for 24 hours
what is daylight
daylight is an exogenous zitegeber
what is the sleep wake cycle governed by
an endogenous peacemaker called the superchiasmatic nucleus
what does the superchiasmatic nucleus do
provides information from the eye about light, light resets the superchiasmatic nucleus
drowsy feeling at night occurs due to the superchiasmatic nucleus
what was Siffres cave study
deprived himself of light to see effects on rhythms
believed he was in august in September 1962
2nd time spent 6 months in a cave
rhythms settled to 25 hours instead of 2hours but sleep wake was relatively on schedule
Aschoff and Wever 1976
participants spent 4 weeks in World War Two bunker deprived of all light
rhythms between 24-25 hours but one extreme 29 hours
suggests circadian sleep wake is closer to 25 hours but exogenous zeitgebers like light bring its down to 24 hours
Follered 1985
12 people lived in a dark cave for 3 weeks
went to bed when clock said 11:45 woke at 7:45
researchers gradually speed up the clock. 24 hour day come 22
only 1/12 adjusted comfortably
suggests the existence of a strong free running circadian rhythm that can’t be overridden by exogenous zitegebers
evaluation shift work
understanding of consequences of desynchronisation and real world implications on worker productivity
night workers experience a drop in concentration around 6am leading to more mistakes (oven et al)
shift workers night 3x more likely to suffer heart disease
however
studies use correlational conclusions so we can’t establish definitively that these negative effects are due to desynchronisation
evaluation medical treatment
real world application; understanding of rhythms - drugs administered according to rhythms
for example heart attacks are more likely to occur in the morning so Aspirin is best taken last thing a night (borten et al)
evaluation individual differences
all research had small sample sizes
difficult to generalise results
sleep wake cycles vary from person to person
Czeisler et al found differences vary from 13-65 hours
duffy et al talked about preference in larks (sleep early) onal owls sleep late
discussion boils down to meaningless averages
folkerad et all children
group of chuldeewn had stories read to them at 3pm had superior recalled and comprehension compared to another group at 9am when tested a week
