Biopsychology year 2 P2 // Endogenous pacemakers and exogenous zeitgebers Flashcards
what is a endogenous pacemaker?
internal body clocks
in mammals, what is the most likely endogenous pacemaker and where is it located?
suprachiasmatic nucelus (SCN) - in the hypothalamus above the optic nerve from each eye cross over.
what does the SCN do in the day?
receives info from the light by the optic nerve - it helps us become in sync with the outside world.
what does the SCN do at night?
sends signals to pineal gland so it produces the hormones melatonin which induces sleep.
what is a exogenous zeitgeber?
external time givers
what is the dominant zeitgeber in the human sleep wake cycle?
sunlight
what would the zeitgebers do if we travelled across different time zones?
the circadian rhythm would become aligned to the new cues - entrainment
what is an example of how social cues may determine the sleep wake cycle?
not determined by sunlight cues, in the UK individuals do not go to bed at dusk because its getting dark (in winter could be late afternoon.)
what supportive evidence is there for endogenous pacemakers in animals?
destroyed connections from the SCN to the brain in chipmunks - had NO sleep wake cycle and many had been killed because they had been awake and asleep at natural times leaving them vulnerable to predators.
what supportive evidence is there for endogenous pacemakers in humans?
Michel siffre spent several periods of time living underground with no light or clocks. after several months his sleep wake cycle settled to a rhythm of 25 hours - regular rhythm must be because of endogenous pacemakers SCN
what practical applications is there from this research about exogenous pacemakers and zeitgebers?
- shift workers - working in very bright light and sleeping in total darkness.
- reduce the effects of jet lag - exposed to a bright light , feel sleepier to help them go to sleep earlier in new time zone.
