exogenous zeitgebers + sleep/wake cycle

• Light

  • can reset SCN
  • indirect influence on key processes - secretion of melatonin

  Campbell + Murphy

  • 15 participants woken various times with light shone on back of knees
  • deviation in sleep/wake up to 3 hors
  • light powerful exogenous zeitgeber that doesn’t need eyes

  social cues

  • 6 weeks: circadian rhythm begins
  • 16 weeks: rhythms entrained by parents schedules - dinner, bed time
  • jet lag: adapting to local eating + sleeping times overcomes jet lag
• exogenous zeitgebers evaluations

  • S: Siffres cave, Aschoff + Weaver, Folkard HOWEVER generalisability: small scale + usually work together
  • W: not universal effect: people in Artic Circle in dark for 6 months, similar sleep/wake all year - primarily controlled by endogenous pacemakers
  • W: evidence challenged role: young blind maan 24.9h sleep/wake not changed with social cues - not effective alone in resetting rhythm