Circadian rhythms Flashcards
(14 cards)
What are circadian rhythms?
Rhythms that last for around 24 hours
What is the sleep wake cycle?
Biological clock - suprachiasmatic nucleus (SCN) - endogenous zeitgeber
SCN lies just above the optic chiasm - provides info from the eye about light
The SCN detects light and tells the pineal gland to stop producing melatonin (sleep hormone)
Exogenous zeitgebers reset or entrain the SCN keeping it to a 24 hour cycle
What was Siffre’s cave study?
Spent several extended periods underground
Deprived of exposure to natural light and sound
Had access to food and drink
Spent 2 months in the caves in the southern alps
Came out mid September
But thought he had resurfaced mid-august
What did Siffre do a decade later?
Performed similar research in texan cave
What did Siffre find?
His ‘free running’ biological rhythm
Settled down to one that was just beyond the usual 24 hours (25 hours)
Continued to fall asleep and wake up at a regular schedule
Concluded we have a free running biological rhythmic clock
What did Aschoff and Wever study?
Asked participants to spend 4 weeks in a WW2 bunker deprived of natural life
What did Aschoff and Wever find?
All but one displayed a circadian rhythm of 24-25 hours
One extended to 29 hours
What did Aschoff and Wever conclude?
Suggesting natural sleep/wake cycle is slightly longer than 24 hours but is entrained with exogenous zeitgiebers
External factors control how we sleep
What did Folkard study?
Group of 12 people
Agreed to live in a dark cave for three weeks
Retiring to bed when the clock said 11.45 pm
Rising when it said 7.45 am
Over course of study researchers gradually sped up the clock (not known to participants) so an apparent 24 hour day eventually only 22 hours
What did Folkard find?
Only one participant was able to comfortably adjust to the new regime
Suggesting existence of strong free running circadian rhythms that cannot easily be overridden by exogenous zietgebers
What is a strength of circadian rhythms?
Practical application
Shift workers experience a period of reduced concentration around 6 am meaning mistakes more likely
3x more likely to develop heart disease
Showing research into the sleep/wake cycle has important real work economic implications in terms of productivity
What is a strength of Circadian rhythms?
Used to improve medical treatments
Chronotherapeutic studies how medical treatment can be administrated in a way to correspond to biological rhythms
Showing that research into circadian rhythms can increase the effectiveness of drug therapies
What is a negative of circadian rhythms?
Individual differences
Studies are based on small samples and sleep wake cycle varies between people
Siffre observed how his cycle slowed with age
Some people are larks and others are owls
Difficult to generalise research into sleep wake cycle
What is a negative of circadian rhythms?
Metholodigal issues
Siffre was exposed to artificial light which may have acted as an exogenous zeitgeber
Research lacks validity
Questions conclusions about the bodies internal clock
