ENDOGENOUS PACEMAKERS AND EXOGENOUS ZEITGEBERS Flashcards
what 3 things must we remember for endogenous pacemakers and sleep/wake cycle?
SCN
animal studies and SCN
pineal gland and melatonin
what is the SCN?
suprachiasmatic nucleus, tiny bundle of cells located in the hypothalamus in each hemisphere of brain
it is one of the….. in mammalian species and is influential in ….
one of primary endogenous pacemakers and is influential in maintaining circadian rhythms
what do nerve fibres connected to eye cross over?
cross in area called optic chiasm on way to visual area of cerebral cortex
where does the SCN lie?
above the optic chiasm
what does the SCN recieve info abt?
abt light directly from the optic chiasm
when does the SCN recieve info abt light?
when we have our eyes open and closed, enabling biological clock to adjust to changing patterns of daylight whilst we are asleep
who conducted animal research into SCN?
DeCoursey et al
Ralph et al
what did DeCoursey et al do?
destroyed SCN connections in brains of 30 chipmunks, returned to habitat and observed for 80 days
what happened to the sleep/wake cycle of chipmunks in DeCoursey et al’s study?
disappeared, end of the study significant proportion of them killed by predators
what happened in the study of Ralph et al?
bred ‘mutant’ hamsters with 20hr wake and sleep cycle
what happened to the hamsters in Ralph et al?
SCN cells from foetal tissue of mutant hamsters transplanted brains of normal hamsters
the cycles of the second groups hamsters….
defaulted to 20 hours
when is the pineal gland active?
during the night
what does the pineal gland increase production of?
melatonin
define melatonin
a chemical that induces sleep and is inhibited during periods of wakefulness
what had melatonin been suggested as a factor in?
a factor in seasonal affective disorder
what are exogenous zeitgebers?
external factors in the environment that reset our biological clocks through entrainment
what happens in the absence of external cues?
free running biological clock controls sleep/wake cycle e.g Siffre
what is the key exogenous zietgeber?
light
what does light reset?
the body’s main endogenous pacemaker
what does light have an indirect influence on?
key processes in the body that control functions such as functions like hormone secretion and blood circulation
who studied light?
Campbell and Murphy
what did Campbell and Murphy demonstrate?
light may be detected by skin receptor sites even when info is not at eyes
what did Campbell and Murphy do?
woke up 15 ppts at various times and light shone onto back of legs, produced deviation is sleep/wake cycle
what does Campbell and Murphy’s study suggest?
light is a powerful exogenous zeitgeber, don’t need to rely on eyes
what is another exogenous zeitgeber apart from light?
social cues
at 6 weeks of age, what begins?
circadian rhythms and by 16 weeks babies are entrained
how are babies entrained into circadian rhythms?
schedules imposed by parents such as mealtimes and bedtimes
what does research suggest about social cues?
adapting to local times for eating and sleeping, is an effective way of entraining circadian rhythms and beating jet lag
