Exogenous zeitgebers

Question 1

What are exogenous zeitgebers?

Answer 1

External factors that affect or entrain our biological rhythms

Question 2

How do exogenous zeitgebers reset out biological clocks?

Answer 2

Process of entrainment
Interaction of internal and external factors

Question 3

How is does light work as an exogenous zeitgeber?

Answer 3

Can reset the bodies main endogenous pacemaker - SCN
Plays role in maintenance of sleep wake/cycle
Indirect influence on processes that control functions like hormone secretion and blood circulation

Question 4

What did Campbell and Murphy study around light?

Answer 4

Light may be detected by skin receptor sites on the body even when the same information is not received by the eyes

Question 5

What was Campbell and Murphy’s study?

Answer 5

15 participants
Woken at various times
Light pad was shone on back of their knees

Question 6

What did Campbell and Murphy find?

Answer 6

Managed to produce a deviation in the participants usual sleep/wake cycle of up to three hours
Suggesting light is a powerful exogenous zeitgeber that need not necessarily rely on the eyes to exert its influence on the brain

Question 7

How are social cues an exogenous zeitgiver?

Answer 7

Babies sleep/wake cycle
New born - pretty much random
6 weeks - circadian rhythms begin
16 weeks - babies rhythms have been entrained by the schedules imposed by parents, including adult determined mealtimes and bed times

Question 8

What do jet lag studies show about social cues?

Answer 8

Adapting to local times for eating and sleeping is an effective way of entraining circadian rhythms and beating jet lag when travelling long distances

Question 9

What is a limitation of exogenous zietgebers?

Answer 9

Not same effect in all environmnets
People who live in places where little darkness in summer and very little light in winter
Artic circle - Similar sleep patterns all year round, despite spending six months in almost darkness
Suggesting sleep/wake cycle is primarily controlled by endogenous pacemakers that can override environmental changes in light

Question 10

What is a limitation of exogenous zeitgebers?

Answer 10

Evidence challenges role of exogenous zeitgebers
Miles et al
Recount the study of a young man
Blind from birth
Had abnormal circadian rhythm of 24.9 hours
Despite exposure to social cues his sleep/wake cycle could not be adjusted
Suggesting social cues alone are not effective in resetting biological rhythm