biological rhythms: circadian rhythms Flashcards
circadian rhytm
one cycle every 24 hours
circadian example - sleep/wake cycle
exogenous zeitgebers - fact we feel drowsy when its night time shows the effect of dyalight
endogenous pacemakers - biological clock
rhythm is governed by the suprachiasmatic nucleus
circadian rhythm research - Siffre
Wanted to find out what his natural sleep-wake cycle would be without any exogenous zeitgebers
2 months in cave
took his pulse and a psychological test
Average cycle = 26 hours
demonstrated the free-running (endogenous pacemaker
circadian rhythm research supporting Siffre - Aschoff and Wever
a groups of participants spent 4 weeks in a bunker deprived of natural light. They found that al but one displayed a circadian rhythm between 24 and 25 hours
Siffre’s experience and this 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.
strenght - application to shift work
shift work creates desynchronisation of biological rhythms
reserach suggests a link between shift work and poor health, with shift workers 3x more likely to develop heart disease
research into sleep/wake cycle may have economic implications in terms of how best to manage shift work
strenght - real world application to medical treatment
circadian rhythms co-ordinate the body’s basic processes e.g heart rate
with implications for chronotherapeutics (timing medication to maximise effects on the body)
aspirin reduces heart attacks, which are most likely in the morning
research found taking ti last thing at night is when it most effective
shows circadian rhythm reserach can help increase effectiveness of drugs
limitation - generalisations ahrd to make
studies of sleep/wake cycle often use small groups of participants
participants may not be representative of the wider population
- limits making meaningful generalisations
prevents general conclusions
melatonin is an endogenous mechanism: sleep/wake cycle
Low levels of light
Melanopsin (sensitive to light) on the retina detects the low levels of light - LVf-RH, RVF-LH
SCN in the hypothalamus receives the information from the optic nerve
Sends signal to the pineal gland
Increases melatonin
Induces sleep
