biopsychology - exogenous and endogenous zeitgebers Flashcards
outline the main endogenous pacemaker in circadian rhythms
Suprachiasmatic nucleus - bundle of nerve cells located in hypothalamus. The SCN receives information about light directly from the optic chiasm even when the eyes are closed. This enables the biological clock to adjust to changing patterns of daylight during sleep.
outline the research supporting the existence of the SCN
Decoursey - destroyed SCN in the brain of 30 chipmunks who were returned to natural habitat and observed for 80 days. Sleep/wake cycle dissapeared and a significant proportion of them had been killed by predators
What conclusions can be drawn from Decoursey’s research
the SCN pacemaker is most influential in regulating sleep/wake cycle. Endogenous pacemakers are more influential than exogenous because they were not strong enough to entrain the chipmunks sleep wake cycle.
what is the issue with using animal research as a mean of testing effect of EP and EZ
although hamsters somewhat biologically similar they are less complex. Humans have higher cognitive functioning so cannot generalise findings to humans completely
what is an endogenous pacemaker
internal mechanisms that govern biological rhythms, in. particular, the circadian sleep-wake cycle
what is an exogenous zeitgeber
external environmental cues that help regulate our internal body clock
where is the suprachiasmatic nucleus found
lies above the optic chiasm
how does the SCN regulate sleep wake cycle
recieves information about light from the hypothalamus then causes the pineal gland so secrete melatonin (if lack of light) and serotonin (if lots of light)
what research evidence is there to support the powerfulness of exogenous zeitgebers.
campbell and murphy shone light on back of the knee where there are skin receptor sites, 15 pps were woken up at various times and a light pad was shone at back of knee, this produced a deviation in participants usual sleep/wake cycle of up to 3 hours.
what conclusions can be drawn from campbell and murphy’s research.
light (an exogenous pacemaker) has a strong influence on the body’s sleep wake cycle and can reset the main endogenous pacemaker the SCN which entrains the sleep wake cycle.
what other exogenous pacemakers are influential other than light, and how
social cues - from just 16 weeks babies become entrained by schedules imposed by parents such as meal times, research shows to cure jet lag a person should eat at local time rather than eating when one is feeling hungry -this can effectively entrain the sleep wake cycle
what validity problems are there in relation to campbell and murphy’s research. (2)
used body temp to measure what stage of circadian rhythm person is in, can be inaccurate when used in isolation, individual differences such as clothes someone is wearing, health conditions ect.
woke up pps in order to shine light, may not be light that entrained the circadian rhythm but the pps becoming used to being woken up and therefore expecting it each night.
what is the practical value of understanding the interaction of ZP and EP .
Led to better understanding of why jet lag occurs (lack of synchrony in circadiam rhythm) and when accidents are more likely occur during night shift work which has helped people minimise the effects of jet lag - social cues, and increase amount of light during time when accidents are more prone.
