endogenous pacemakers Flashcards
define endogenouse pacemakers
– internal body clocks that regulate many of our biological rhythms, such as the influence of the suprachiasmatic nucleus (SCN) on the sleep/wake cycle.
what is the suprachiasmatic nucleus
a tiny bundle of nerve cells in the hypothalamus which helps maintain circadian rhythms
what do nerve fibres do
travel from the eye cross at the optic chiasm on their way to the visual cortex.
where dose the SCN lie
above the optic chiasm
what dose the SCN do
receives information about light
who studied chipmunks and the SCN
DeCoursey et al. (2000)
what did DeCoursey et al do
destroyed SCN connections in the brains of 30 chipmunks
returned to their natural habitat and observed for 80 days.
what did DeCoursey find
Their sleep/wake cycle disappeared and many were killed by predators.
who studied hamsters and sleep wake cycles
Ralph et al. (1990)
what did Ralph et al. do
bred ‘mutant’ hamsters with a 20-hour sleep/wake cycle
SCN cells were transplanted from the foetal tissue of these hamsters into the brains of normal hamsters,
what did Ralph et al find
hamsters developed cycles of 20 hours.
what are two endogenous mechanisms
The pineal gland and melatonin
what increases melatonin production
The SCN passing information on day length to the pineal gland
