Endogenous Pacemakers and Exogeneous 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 about?
about light directly from the optic chiasm
when does the SCN recieve info about 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
define melatonin
hormone produced by the pineal gland in the brain that regulates the body’s sleep-wake cycle
what had melatonin been suggested as a factor in?
may participate in the physiological regulation of sleep
what are exogenous zeitgebers?
external environment cues that help regulate our internal body clock. Include factors such as light, temperature, and social cues
what happens in the absence of external cues?
significantly alters circadian rhythms
what is the key exogenous zeitgeber?
light
