effect of endogenous pacemakers and exogenous zeitgebers on sleep wake cycle

Question 1

What is the sleep wake cycle controlled by?

Answer 1

• endogenous pacemakers are internal factors
• help to maintain our biological rhythm
• also rhythms are entrained (synchronised) by exogenous zeitgebers
• which are external factors e.g. light

Question 2

Endogenous pacemakers

Answer 2

• internal body clock
• controlled by master endogenous pacemaker - suprachiasmatic nucleus (SCN)
• found in hypothalamus
• eyes notice change in light - gets dark - less light received by retina
• sends information to SCN
• stimulates pineal gland to release melatonin - promote sleep
• eyes detect light (EZ) - SCN reset
• stimulates SCN and pineal gland - inhibits release melatonin - produce wakefulness

Question 3

Exogenous zeitgebers

Answer 3

• external factors in our environment
• influence our sleep wake cycle
• through entrainment (synchronise)
• e.g. light - resets SCN

Question 4

Effect of social cues on our sleep wake cycle

Answer 4

• social cues e.g. meal times, social interaction influence sleep wake cycle
• make us less alert once finished evening meal
• research suggest adapting to local eating and sleeping time before travel different time zone prevent jet lag - so EZ affect cycle

Question 5

What happens when our sleep wake cycle is disrupted?

Answer 5

• occur for many reasons e.g. jet lag, shift work
• consequences:
  . difficulty sleeping (hard to fall asleep or sleep whilst driving)
  . decreased attention (leads to accidents)
  . digestive problems
  . tiredness
  . poor reasoning skills
  . increases anxiety and irritability

Question 6

How could we maintain our sleep wake cycle? (AO2)

Answer 6

• follow local eating times
• follow local sleeping times
• stimulate yourself during the day - be social and active
• use blackout curtains - limit artificial light
• don’t use phone late at night

Question 7

AO3 for EP and EZ on the sleep wake cycle: RTS by DeCoursey

Answer 7

P - RTS effect EP on sleep wake by DeCoursey et all (2000)
E - destroyed SCN connection brains 30 chipmunks - returned to natural habitat - observed 80 days
E - sleep wake cycle disappeared - end of study significant amount killed by predators - as awake and vulnerable to attack - should have been asleep
L - supports influence important EP (SCN) on maintain sleep wake - EZ alone not able maintain sleep wake

Question 8

AO3 for EP and EZ on the sleep wake cycle: Discuss - animal bias

Answer 8

P - research into impact EP on sleep wake critisied animal bias
E - potentially problem - humans more complex biological rhythms - as higher mental functioning
E - issue extrapolating findings of research to humans
L - limits extent DeCoursey’s findings support important EP on sleep wake

Question 9

AO3 for EP and EZ on the sleep wake cycle: RTS by Siffre

Answer 9

P - RTS role EP on sleep wake by Siffre
E - isolated himself in cave for 6 months - no EZ e.g. light dark - found within few days developed consistent 25 hour cycle - continued to fall asleep and wake up on regular schedule
E - suggest sleep wake controlled by EP

CA - some argue cause Siffre’s sleep wake cycle adjust to longer than 24 hours EZ important in maintain cycle

Question 10

AO3 for EP and EZ on the sleep wake cycle: Discuss - Siffre

Answer 10

P - Siffre’s research lacks ecological validity
E - highly controlled environment
E - not reflect how EP and EZ interact in real life - only exceptional circumstances EP free running unaffected by EZ - real life EP and EZ work together - little sense separate two for purpose of research
L - reduces external validity findings - can’t be generalised - explain how EP impact sleep wake cycle real life