exogenous zeitgebers and the SWC

Question 1

what are exogenous zeitgebers?

Answer 1

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

Question 2

what happens to the SWC in the absence of external cues?

Answer 2

• free-running biological clock that controls SWC continues in a distinct cyclical pattern (siffre)
• free-running cycle is entrained by environmental cues
• SWC has an interaction of internal and external factors

Question 3

light in SWC

Answer 3

• key zeitgeber in humans
• can reset body’s main EP, the SCN
• indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation

Question 4

light: campbell and murphy (1998) - findings

Answer 4

demonstrated that light may be detected by skin receptor sites on the body even when the same info is not received by the eyes

Question 5

light: campbell and murphy (1998) - procedure

Answer 5

• 15 participants were woken at various times and a light pad was shone on the back of their knees
• researchers managed to produce a deviation in pps’ usual SWC by up to 3h in some cases
• suggests that light is a powerful EZ that doesn’t rely on the eye to exert its influence on the brain

Question 6

social cues: babies

Answer 6

• babies rarely have same SWC as the rest of the family
• newborn babies’ initial SWC is random
• at about 6 weeks, the circadian rhythm begins
• by 16 weeks, babies’ rhytms have been entrained by the schedules imposed by parents, including adult-determined mealtimes and bedtimes

Question 7

social cues: jet lag

Answer 7

research on jet lag suggests that adapting to local times for eating and sleeping (rather than responding to own feelings of hunger and fatigue) is an effective way of entraining circadian rhythms and beating jet lag when travelling long distances

Question 8

evaluation: EZs do not have the same effect in all environments

Answer 8

• experience of people who live in places where there is very little darknes in summer and very little light in winter tell us a different story
• people who live within arctic circle (eg. inuits of greenland) have similar sleep patterns all-year round, despite spedning ~6 months in total darkness
• SWC is primarily controlled by EPs that can override environmental changes in light

Question 9

evaluation: case study evidence challenges role of EZs

Answer 9

• miles et al. (1997) recount the study of a young man, blind from birth, who had an abnormal circadian rhythm of 24.9h
• despite exposure to social cues, such as regualr mealtimes, his SWC could not be adjusted
• this suggests that social cues alone are not effective in resetting the biological rhythm

Question 10

evaluation: age-related insomnia (EP)

Answer 10

• evidence suggests that people have poorer quality sleep as they get older
• this may be due to natural changes in the circadian rhythm as we age, which means falling asleep earlier and broken sleep at night (duffy et al. (2015)

Question 11

evaluation: age-related insomnia (EZ)

Answer 11

• studes have suggested that exogenous zeitgebers may be more responsible for the changes in sleep patterns amongst older people
• hood et al. (2004) found that management of onsomnia was improved if elderly people were generally more active and had more exposure to natural light