A03

• * evidence to support role of scn by ralph?

  • took scn from mutant breed of golden hamsters with c.r of 20 hours & transplanted it into hamster with normal 24hr rhythm
  • normal hamster showed shorter rhythm similar to hamster whose scn had received
  • shows lab based evidence for role of scn in controlling sleep/wake cycle
  • by manipulating hamsters scn sleep/wake cycle completely changed
• * evidence to support e.p regulates sleep/wake cycle by siffre?

  • cave explorer who spent 6 months in underground cave to deprive himself of natural light & sound
  • was completely cut off from e.z
  • after period of time cycle settled to 25 hrs not dissimilar from standard 24hr cycle in real world
  • shows real world evidence for role of scn in controlling sleep/wake cycle
  • even without environmental influences (light/social cues) was able to stick to rough 24 hr sleep/wake cycle
• * evidence to supprt role of e.z by campbell & murphy?

  • applied light to back of knees of 15 p - detected by receptors in skin
  • resulted in shift in p usual cycle of upto 3 hrs
  • suggests external cues can affect cycle
  • lab based experiment used artificial light to manipulate cycle by resetting scn & can also provide entrainment to change shift in b.r
• * practical application?

  • shift workers who do night shifts have period of reduced concentration at 6am - mistakes & accidents more likely to occur
  • advice of things to avoid (light) can be given so can sleep during day & be more productive at work on night shifts & less error prone
  • helpful to know as it means people who work night shifts can adjust behaviour so can minimise effects of sleep disruption
  • research is valuable for society
  • more productive & less error prone workforce good for economy
  • people getting more sleep so less likely to suffer negative health outcomes from poor sleep
• 3 X of circadian rhythms?

  1. use of case study in siffre
  2. use of animals in ralphs
  3. sample of campbell & murphy