SECTION: Endogenous Pacemakers and Exogenous Zeitgebers
TOPIC: Biopsychology
Endogenous Pacemakers - Internal body clock that regulates biological rhythms.
Suprachiasmatic Nucleus SCN – Located in the hypothalamus the structure receives light information and adjusts
bodily activities. With a higher light exposure, the SCN will control the release of melatonin, reduced the amount
but at night the release of melatonin increases causing drowsiness.
Animal Study: In 1990, Ralph et al, bred hamsters with the sleep/wake cycle of 20 hours, he then transplanted
their SCN into the brains of regular hamsters and found the regular hamsters cycle changed from 24 hours to 20
hours.
Exogenous Zeitgebers – External factors that entrain our biological rhythms.
Light – It plays a role in the sleep/wake cycle, with the ability to reset the SCN. Indirect impacts also occur on
hormone release and blood circulation.
Social Cues – Schedules imposed by everyday demands including mealtimes can entrain the body into a regular
24 hour sleep/wake cycle.
Research into jet lag found that adapting straight away to local meal times and sleep is an effective way to re-set
the circadian rhythm.
WEAKNESS:
- Difficulty of investigation – factors cannot be totally isolated in studies of EP. Even in Siffre’s cave study, he used artificial
light which could’ve impacted his cycle. Also, in everyday life the body clocks work together and therefore there may be
no need to separate them to investigate them.
TOPIC: Biopsychology
Endogenous Pacemakers - Internal body clock that regulates biological rhythms.
Suprachiasmatic Nucleus SCN – Located in the hypothalamus the structure receives light information and adjusts
bodily activities. With a higher light exposure, the SCN will control the release of melatonin, reduced the amount
but at night the release of melatonin increases causing drowsiness.
Animal Study: In 1990, Ralph et al, bred hamsters with the sleep/wake cycle of 20 hours, he then transplanted
their SCN into the brains of regular hamsters and found the regular hamsters cycle changed from 24 hours to 20
hours.
Exogenous Zeitgebers – External factors that entrain our biological rhythms.
Light – It plays a role in the sleep/wake cycle, with the ability to reset the SCN. Indirect impacts also occur on
hormone release and blood circulation.
Social Cues – Schedules imposed by everyday demands including mealtimes can entrain the body into a regular
24 hour sleep/wake cycle.
Research into jet lag found that adapting straight away to local meal times and sleep is an effective way to re-set
the circadian rhythm.
WEAKNESS:
- Difficulty of investigation – factors cannot be totally isolated in studies of EP. Even in Siffre’s cave study, he used artificial
light which could’ve impacted his cycle. Also, in everyday life the body clocks work together and therefore there may be
no need to separate them to investigate them.
