Endogenous Pacemakers Flashcards
What is the suprachiasmatic nucleus?
SCN is a tiny bundle of nerve cells located in the hypothalamus of each hemisphere
primary endogenous pacemaker in mammals and is influential in maintains circadian rhythms such as the sleep/wake cycle
How does the SCN work
lies just above the optic chiasm
received information about light directly from this structure
continued even when our eyes are closed, enabling our biological clock to adjust to changing patterns of daylight whilst we sleep
Describe studies into the influence of the SCN
DeCoursey et al destroyed the SCN connections in the brains of 30 chipmunks who were then returned to their natural habitat and observed for 80 days
found that their sleep/wake cycle disappeared and a significant proportion were killed by predators as they were awake and vulnerable when they should have been sleeping
Describe the role of the pineal gland and melatonin
SCN passes information to the pineal gland which is another endogenous mechanism guiding the sleep/wake cycle
during the night the pineal gland increases production of melatonin which is a chemical that induces sleep and is inhibited during wakefulness
What are the limitations of endogenous pacemakers
SCN may obscure other body clocks
Damiola et al demonstrated how changing feeding patterns in mice could alter the circadian rhythms of liver cells by up to 12 hours whilst leaving the SCN unaffected
suggest other complex influences on the sleep/wake cycle
they cannot be studied in isolation
in everyday life, pacemakers and zeitgebers interact however many studies separate the two for the purpose of research
the more researchers attempt to isolate the influence of endogenous pacemakers, the lower the validity of the research
