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EDOGENOUS PACEMAKRES AND EXOGENOUS ZEITGEBERS - Coggle Diagram
EDOGENOUS PACEMAKRES AND EXOGENOUS ZEITGEBERS
SCN
SCN is a cluster of nerve cells in the hypothalamus
the 'master clock', links to other brain regions that control sleep and arousal , has control over other biological clocks throughout the body
endogenous pacemakers: internal body 'clocks' that regulate biological rhythms
The peripheral clocks (eg reproductive systems) can maintain a circadian rhythm but not for very long, which is why they must be controlled by the SCN
Ralph et al. 1990
they transplanted the SCN cells into hamsters, which had no such abnormalities
the hamsters circadian rhythm shortened to 20 hours, they adopted the rhythm of the implanted SCN
removed the SCN out of genetically abnormal hamsters which only had a circadian cycle of 20 hours
suggests the importance of the SCN in regulating circadian rhythms
animal research - extrapolation issues
siffre + for evaluation
exogenous zeitgebers
melanopsin (a protein), which is sensitive to light is key to this system
cells (containing melanopsin) carry signals to the SCN to set the daily body cycle
there is a light detecting cell in the retina that gauges overall brightness to help rese the internal biological clock
environmental cues, such as light, that help to regulate the sleep/wake cycle in an organism
Steel et al 2008
5/6 of ppts developed a free running sleep/wake cycle longer than 24 hours
sleep patterns were also found to be individual, no synchrony between ppt
investigated the effects of constant daylight on circadian rhythms by monitoring six ppts living in the artic
suggests that social cues do not effect in entraining sleep wake cycle in the absence of other key zeitgebers
exogenous zeitgebers : social cues
burgess et al. - found that exposure to bright light prior to west - east (eg, USA -> UK) flight decreased the time needed to readjust to local time on arrival
eg. mealtime, social times, alarm clocks