endogenous pacemakers and exogenous zeitgebers Flashcards
(15 cards)
what is the suprachiasmatic nucleus
a tiny group of nerve cells in the hypothalamus, one of the primary endogenous pacemakers and essential for circadian rhythms such as the sleep-wake cycle
what is the optic chiasm
sends info about light to the scn, continues when we are asleep which allows our biological clock to adjust to changing patterns of daylight while we are asleep
what was decoursey et al’s study and what did they find
destroyed scn connections in the brains of 30 chipmunks who were returned to their habitat and observed for 80 days. the sleep wake cycle disappeared and by the end most of them had been killed by predators as they were awake and vulnerable to attack when they shouldve been asleep
what was martin ralph’s study and what did he find
bred mutant hamsters with a 20 hour sleep wake cycle. when scn cells from the foetal tissue of mutant hamsters were transplanted into the brains of normal hamsters their cycle defaulted to 20 hours. this emphasises the role of the scn in circadian rhythms.
the scn passes info on day length and light to what
the pineal gland just behind the hypothalamus
during the night what does the pineal gland increase production of
melatonin to induce sleep, inhibited when awake
what does light also have an influence on
functions such as hormone secretion and blood circulation
what was campbell and murphys study and what did it show
demonstrated that light may be detected by skin receptor sights as well as the eyes. 15 ps were woken at various times and a light pad was shone on the back of their knees. in some cases this deviated the sleep wake cycle up to three hours, suggesting it does not necessarily rely on the eyes
what is the initial sleep wake cycles in babies like
random
at about 6 weeks of age what begins and by how many weeks are they embedded
circadian rhythms, 16 weeks
what is a big influence on the sleep wake cycles of babies
schedules imposed by parents that determine meal and bed times
research has revealed that there are circadian rhythms in what organs and cells (and what are these called)
peripheral oscillators
adrenal gland, oesophagus, lungs, liver, pancreas, liver, spleen and the skin
how is damiola et al a weakness
demonstrated how changing feeding patterns in mice could alter the circadian rhythms of cells in the river by up to 12 hours whilst leaving the scn rhythm unaffected. this suggests that there may be many other complex influences on the sleep wake cycle apart from the scn
how are animal studies a weakness
difficult to generalise, exposed to considerable harm so ethical issues
how is miles et al a weakness of exogenous zeitgebers
a man blind from birth had a circadian rhythm of 24.9 hours. despite exposure to social cues his sleep wake cycle did not adjust and he had to take sedatives to sleep at night. also studies of people in arctic regions where the sun does not set in the summer show normal sleep patterns. this shows how exogenous zeitgebers have little influence on our internal body clock
