Discuss research into circadian rhythms. Refer to evidence in your answer. [16 marks]

AO1

• A type of biological rhythm, (patterns of change in the body’s physiological state governed by exogenous zeitgebers and endogenous pacemakers), that repeats every 24 hours

• e.g. the sleep-wake cycle

  • we feel sleepy at night and alert during the day, is it free-running? influenced by…

    • ep: SCN (in the hypothalamus) detects changes in light, signals pineal gland to release melatonin, cause of sleepiness

    • ez: light and socialisation

  • Michel Siffre, cave study, no outside influences (people, natural light etc), biological clock left to run free, sleep-wake cycle extended to a consistent 25 hour loop, therefore cr strong but influenced by external factors

  • Folkard, cave study, unknowingly decreased time in a day, ppts did not cope, threrefore free-running circadian rhythm strong, not easily overridden

AO3

• criticise Siffre’s research as un-generalisable due to case study nature, individual differences e.g. ‘owls’ vs ‘larks’, Siffre himself showed variation in a later recreation

• poor control, artificial light in Siffre (1962) could have acted on body clock, ‘reset’ it each morning

• other recreation from Aschoff and Wever supported, 25 hour cycle, but presence of a group could have been an exogenous zeitgeber, did not isolate effect of only the biological clock

• application to healthcare, pharmacokinetics, when best to administer drugs in the day for best absorption and circulation

• application to shift work and minimising detrimental impacts of a disrupted circadian rhythm (Knutsson 2003)/(Boivin)