Endogenous pacemakers and exogenous zeitgebers Flashcards
Endogenous pacemakers
Internal body clocks that regulate biological rhythms
Exogenous zeitgebers
External factors that affect our biological rhythms
Research on endogenous pacemakers
DeCoursey:
- Destroyed SCN connections in 30 chipmunks who were then returned to their habitat and observed
- Their sleep/wake cycle had disappeared
- A significant number of chipmunks had been killed by predators as they were awake and vulnerable to attack when they should’ve been asleep
Ralph:
- Bred mutant hamsters with 20 hour sleep/wake cycle
- SCN cells were taken and transplanted into normal hamsters
- The sleep/wake cycle of normal hamsters defaulted to 20 hours
Research on exogenous zeitgebers
Campbell and Murphy:
- 15 p’s were woken at various times and a light pad was shone on the back of their knees
- Managed to produce a change in p’s usual sleep/wake cycle of up to 3 hours
Jet lag studies:
- Have shown that adapting to local times for eating and sleeping is an effective way of entraining circadian rhythms and beating jet lag when travelling
Endogenous pacemakers - evaluation - strength
- Similar structures
- Existence of SCN and pineal gland of chipmunks and hamsters are similar to humans so generalisation can be made
Endogenous pacemakers - evaluation - limitation
- Endogenous pacemakers can’t be studied separately
- In everyday life endogenous pacemakers and exogenous zeitgebers work together
- Suggests any attempts to study them separately lowers the validity of the research
Exogenous zeitgebers - evaluation - limitation
- Don’t have the same effect in all environments
- e.g people who live in places like the arctic circle have similar sleep patterns all year round even though they spend around 6 months in total darkness
- Suggests sleep/wake cycles is primarily controlled by endogenous pacemakers that can override environmental factors e.g light
