biological rhythms: circadian rhythms Flashcards
(23 cards)
What are biological rhythms governed by?
The body’s internal biological ‘clocks’ (endogenous pacemakers) and external changes in the environment (exogenous zeitgebers).
Define circadian rhythms.
Rhythms that last for around 24 hours.
What is an example of an exogenous zeitgeber?
Daylight.
What is the suprachiasmatic nucleus (SCN)?
A biological ‘clock’ in the brain that governs the sleep/wake cycle.
What did Siffre’s cave study investigate?
The effects of the absence of external stimuli on his biological rhythms.
What was the finding of Siffre’s cave study?
His ‘free-running’ biological rhythm settled to around 25 hours.
What did Aschoff and Wever’s bunker study find?
Participants’ sleep/wake cycles extended to between 24 and 25 hours in the absence of natural light.
What did Folkard et al.’s dark cave study reveal?
That only 1/12 participants could comfortably adjust to an apparent 22-hour day, showing that a strong free-runnning circadian rhythm cannot easily be overridden by exogenous zeitgebers.
What is a consequence of disrupted circadian rhythms?
Desynchronisation
How are circadian rhythms linked to medical treatment?
They coordinate bodily processes such as heart rate, digestion, and hormone levels - knowledge of circadian rhythms has been used to improve medical treatments of these.
Why is aspirin more effective when taken at night?
Because heart attacks are most likely to occur in the morning - this has been supported by research into circadian rhythms.
What is a limitation of circadian rhythm research?
Generalisations are difficult due to individual differences in sleep/wake cycles.
What did Czeisler et al. find about sleep/wake cycles?
Individual differences in sleep/wake cycles varying from 13 to 65 hours.
How do circadian rhythms apply to the concept of ‘larks’ and ‘owls’?
‘Larks’ prefer to go to bed early and rise early, whereas ‘owls’ prefer the opposite, showing that there may be individual differences.
What recommendation did Wolfson and Carskadon make regarding school start times?
That the school day should start later to align with teenage sleep patterns.
How does shift work affect circadian rhythms?
It can disrupt them
What did Solomon (1993) conclude about shift work?
High divorce rates in shift workers might be due to the strain of deprived sleep and other influences.
What is chronotherapeutics?
Administering medical treatment in a way that corresponds to a person’s biological rhythms.
How do circadian rhythms affect heart rate, digestion, and hormone levels?
They coordinate these basic processes
What does research suggest about teenagers and sleep?
Teenagers tend to be sleepier at the start of the school day due to hormonal shifts.
What are ultradian rhythms?
Rhythms that occur multiple times during 24 hours.
What are infradian rhythms?
Rhythms that take longer than 24 hours to complete.
What are circannual rhythms?
Rhythms that take much longer than 24 hours to complete.
