examples of endogenouspacemakers that could impact circadian rhythms include systems that release hormones such as melatonin for sleep. Systems that regulate body temperature and systems that control metabolism and digestion.
the main system that controls circadian rhythms is the superchiasmatic nucleus
these internal processes (endogenous pacemaker) are influenced by exogenous zeitgebers- perhaps the most obvious of which is sunlight (sleep wake cycle). For example, the darkness of night is thought to trigger melatonin release, which makes you feel tired and want to go to bed.
Endogenous pacemakers appear to be more important than exogenouszeitgebers in regulating circadian rhythms. there are many studies where circadian rhythms remain despite significant disturbances to exogenous zeitgebers. EG Siffre cave studies, Aschoff and Wever with the world war 2 bunker,
methodological concerns- much of the research on Circadian rhythms is in the form of case studies or experiments using small sample sizes. As such, these findings may not be valid when applied to the general population.
