circadian rhythms Flashcards
Biological rhythms
Controlled by internal body clocks (endogenous pacemakers) and external cues (exogenous zeitgabers) - cyclical time periods
Circadian rhythms
Biological rhythms - subject to a 24-hour cycle - regulate a number of body processes such as the sleep/wake cycle and changes in core body temp
Endogenous pacemakers
Body’s internal biological clock
Exogenous zeitgebers
Changes in the environment
Sleep/wake cycle
Governed by daylight and by biological clock (suprachiasmatic nucleus), get light information from the eyes
Siffre’s cave study
- Extended periods undergroup - effects of own biological rhythms
- Free-running rhythm extended slightly to 25 hours when deprived of daylight
Aschoff and Wever
- Group of participants - 4 weeks in ww2 bunker - no natural light
- Between 24 and 25 hour cycle
Simon Folkard et al
- Group of 12 people - live in dark cave for 3 weeks
- Went to bed at 11.45, rising at 7.45
- Sped clock gradually - only 22 hours
- Only one of participants was able to comfortably adjust
Shift work
- Understanding of consequences that occur when circadian rhythms are disrupted
Reduced concentration at 6am, more accidents (Boivin et al)
Heart disease three times more likely (Knutsson)
Shift work counterpoint
Studies are correlation - effects may be due to disruptive social routines (Solomon)
Medical treatment
- Help improve medical treatments
Timing of drugs (Chronotherapeutics), aspirin more effective at night for heart attack (Bonten et al)
Individual differences
- Limitation - generalisations are difficult to make
- Cycle lengths vary (13 to 65 hours, Czeisler et al), ‘larks’ and ‘owls’ (Duffy et al) - generalisations may be meaningless
Shifting the school day
- Wolfson And Carskadon
- Sleep should start a couple hours later
- Teenage chronotype means sleepy in morning, so shift school day but disruptive for others such as parents and teachers and limits extracurricular activities
