Biopsychology: Circadian Rhythms Flashcards
What is a Biological Rhythm?
Distinct patterns of changes in body activity that conform to cyclical time periods. Biological rhythms are influenced by endogenous pacemakers and exogenous zeitgebers.
What is a circadian rhythm?
A biological rhythm subject to a 24-hour cycle.
Who studied circadian rhythms?
Michael Siffre
What did Siffre do and find?
He went underground for two extended periods with no exposure to natural light and both times his biological rhythm settled around 25 hours.
What research supports Siffre?
Aschoff and Wever
Group of participants spent 4 weeks in a WW2 bunker deprived of natural light
All but one participant displayed a circadian rhythm of 24 to 25 hours.
What do Siffre and the bunker study suggest?
That the natural sleep wake cycle is slightly longer than 24 hours but is entrained by exogenous zeitgebers associated with our 24 hour day.
What studied criticised the influence of environmental cues?
Folkard found we shouldn’t overestimate the influence of environmental cues.
What did Folkard do?
a group of 12 people who agree to live in a cave for 3 weeks who wen to bed when the clock said 11:45pm and woke when it said 7:45am.
Researchers gradually sped up the clock so the day only lasted 22 hours.
What did Folkard find?
Only one participant could comfortably adjust to the new regime.
The circadian rhythm cannot be easily overridden by changes in the external environment.
What are the evaluation points for circadian rhythms?
Practical application to shift work
Practical application to drug treatments
Use of case studies and small samples
Poor control in studies
Circadian rhythms evaluation point: Practical application to shift work
Night workers engaged in shift work experience a period of educed concentration at 6 in the morning meaning mistakes and accidents are more likely (Bolvin).
Therefore research into the s/w cycle my have economic implication in terms of how best t manage worker productivity.
Circadian rhythms evaluation point: Practical application to drug treatments
Circadian rhythms coordinate heart rate, digestion ad hormone levels etc. This has an effect on pharmacokinetics. research has found there are peak times when drugs are at their most effective.
This has led to timing guidelines of drug dosing for a range of medications.
Circadian rhythms evaluation point: Use of case studies and small samples
The studies tend to involve small groups of people. The people may not be representative of the wider population and this limits the extent to which meaningful generalisation and conclusions can be made.
Circadian rhythms evaluation point: Poor control in studies
Although the participants in the studies were deprived of natural light they often had access to artificial light. Siffre turned on a lamp every time he woke up until he went to sleep. However Czeisler was able to adjust a groups rhythms with dim lighting.
