Endogenous pacemakers and exogenous zeitgebers

• The main endogenous pacemakers

  • Suprachiasmatic nucleus
  • Pineal gland
• The main exogenous zeitgebers

  • Light
  • Melatonin
• The effects of light

  • Campbell and Murphy - light on back of the knee, suggests that light can reset biological rhythms through alternate pathways, not just the eyes
  • However, Wright and Czeisler - failed replication
  • Measured body temp and melatonin levels and did not find any shift in the circadian clock
  • This confirms that circadian rhythms are primarily maintained via eyes and SCN/pineal system
• Other exogeneous zeitgebers

  • Social cues - meal times, bed times
  • Temperature - environmental temperature changes
  • Sound - environmental noise, signals to wake
• The effect of sleep disruption

  • Moderate effects - poorer judgement, memory
  • Severe effects - strokes, hallucinations and mood swings
• Sleep disruption and babies

  • Schedule - meal times, bed times
  • Light - keep room dark at night and light during day
  • Social interaction during day
• Sleep disruption and jet lag

  • Eat and sleep in accordance to new time zone
  • Keep busy during day