circadian rhythms Flashcards
What are biological rhythms?
Patterns of change in body activity
What are biological rhythms governed by?
Endogenous pacemakers - internal biological clocks
Exogenous zeitgebers - external changes in environment
What are circadian rhythms?
Last for around 24 hours
What are two examples of circadian rhythms?
Sleep/wake cycle
Core body temperature
What is the sleep/wake cycle?
Drowsy at night - effect of daylight (EZ) on our cycle
Describe Siffre’s cave study
What would happen if we left our sleep/wake cycle without daylight (free-running)?
Stayed underground for 2 months without natural light - was September but thought it was August
Free running biological clock settles to around 25 hours
Describe Aschoff and Wever’s study
Participants stayed 4 weeks in bunker without natural light
All but one had circadian rhythm of 24-25 hours
Natural sleep/wake cycle is 25 hours but is entrained by EZs
Describe Folkard’s research
Participants lived in cave for 3 weeks
Slept at 11:45 and woke at 7:45
Researchers sped up clock so days were only 22 hours
Only one participant could adjust
Suggests natural rhythm can’t be easily overridden by external changes
Evaluation - practical application to shift work
Night workers experience a period of reduced concentration at 6am - circadian trough
Accidents more likely
Shift workers more likely to develop heart disease
Economic implications - how best to manage worker productivity
Evaluation - practical application to drug treatments
Circadian rhythms coordinate basic processes eg heart rate
Effect on pharmakinetics - action of drugs on body
Research shows there’s peak times when drugs are most effective
Evaluation - case studies and small samples
Aschoff and Wever - small sample
Siffre - case study
Do not represent wider population
At age 60 Siffre realised his body clock was slower as a young man
Evaluation - poor control in studies
Had access to natural light
Turned on lamp when he woke up
Czeisler - able to increase rhythm from 22 to 28 hours using dim lighting
Evaluation - individual differences
Individual sleep/wake cycles can vary - 13 to 65 hours
Duffy - larks and hours (natural preference for when they sleep)
