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Slide 1

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Biological Rhythms and Sleep…read more

Slide 2

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Biological Rhythms
Circadian ­ 24 hour cycle
Sleep/Wake Cycle
Ultradian ­ more than once every 24 hours
Sleep cycle
Heart beat
Infradian ­ less than once every 24 hours
Menstrual Cycle
Circannual ­ Annual cycle
Hibernation…read more

Slide 3

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Control of Biological Rhythms
Exogenous Zeitgebers
external factors that influence biological rhythms
Endogenous Pacemakers
Biological clock which are influenced by exogenous zeitgebers
Regulates rhythms within the body…read more

Slide 4

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Circadian Rhythm ­ Sleep/Wake Cycle EZ'
s and EP's
Connected by
Light falls on retina of
optic nerve to
SCN causes pineal
- EZ gland to increase
- EP serotonin and decrease
Melatonin induces sleep
Person wakes
up…read more

Slide 5

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Research on EP
Removed SCN from hamsters
Caused them to lose circadian rhythm
Transplanted SCN back to hamsters
Circadian rhythm was re-established
Evaluation of Research
· Did show SCN acting as an EP
· Ethical issues
· Cannot be generalised to humans
· Lacks ecological validity…read more

Slide 6

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Research on EP
Lab study
Measured melatonin and sleepiness in participants
Every 20 minutes for 29 hours
Found ­ melatonin was secreted 2 hours before highest level of sleepiness
Evaluation of Research
· Conducted on human participants
· Successfully shows melatonin as an EP
· Lacks ecological validity…read more

Slide 7

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