exogenous zeitgeibers

Question 1

discuss light as an exogenous zeitgeiber

Answer 1

• light is a key exogenous zeitgeiber and can reset the bodys main endogenous pacemaker ( SCN) and therefore plays a role in the maintenance of the sleep wake cycle
• aso has a direct influence on processes in the body that control functions like hormones secretion and blood circulation

Question 2

discuss social cues as an exogenous zeitgeiber

Answer 2

• the sleep wake cycle of babies is essentially random
• but, at about 6 weeks, circadian rhythms begin and at about 16 weeks babies rhythms have been entrained by the schedules imposed by their parents including those relating to mealtimes and bedtimes

Question 3

what is a limitation of exogenous zeitgeibers (environmental effect)

Answer 3

don’t have the same effect in all environments. eg, the inuits of the arctic cycle who spend 6 months of the year in total darkness nevertheless have the same sleep wake cycle all year long, suggests endogenous pacemakers are much more important in regulating the sleep wake cycle than exogenous zeitgeibers such as light

Question 4

what is a limitation of exogenous zeitgeibers (case study evidence)

Answer 4

a number of case studies suggest that the effect of exogenous zeitgeibers on the sleep wake cycle has been exaggerated. eg a Case study conducted by miles et al found that a young man blind from birth had an abnormal circadian rhythm of 24.9 hours despite exposure to social cues such as regular mealtimes, suggesting cues alone are insufficient to determine the sleep wake cycle, and other factors must be involved

Question 5

what is an exogenous zeitgeiber

Answer 5

external factors in the environment such as light that reset our biological clocks through a process known as entrainment