Biopsych: Endogenous pacemakers and exogenous zeitgebers Flashcards
The main Endogenous pacemakers
superchiasmatic nucleus (SCN)
Where’s the SCN located?
hypothalamus in both hemispheres
Example of how the SCN works
In reference to the SWC the SCN receives info about light via optic nerve fibres, this happens even when eyes are shut. SCN acts as a master clock using light levels to regulate bio rhythms including to feel sleepy or awake. The superchiasmatic nucleus regulates bio rhythms by passing info about light and day length to pineal gland behind the hypothalamus. At night the pineal gland increased melatonin production and on the day the production is decreased. The function as endogenous pacemakers but is still determined by light.
What’s entrainment?
the process by which an exogenous zeitgeber resets a bio clock
How does entrainment work?
Light influences the SWC, hormone secretion and blood circulation. Light can be detected through the optic nerve and in skin receptor sites such as the back of the knees as shown though research. Light was shone on the back of ppts knees which successfully changed sleep-wake cycles by up to 3 hours. Social cues influence bio rhythms in babes —> when born babies have a random sleep-wake cycle. After 16 weeks bio clocks are set ‘entrained’ by meal and bed timed from parents. Similarly in adults, countering jet lag is another social cues – meal and bed files if the locals can help to entrain bio clock to local time.
AO3 for Endogenous pacemakers and exogenous zeitgebers
+Evidence suggests that people have poorer quality sleep as they get older
-Limitation of describing the SFN as the ‘master clock’
-Influence of exogenous zeitgebers on sleep-wake cycle may be overstated/deterministic
-Interactionist approach may be more appropriate when identifying influences on the sleep-wake cycle
(+AO3) Evidence suggests that people have poorer quality sleep as they get older
Evidence suggests that people have poorer quality sleep as they get older. This may be due to natural changes in the circadian rhythm as we age, which means falling asleep earlier and breaking sleep at night (Duffy et al, 2015). However, studies have suggested that exogenous factors may be responsible for the changes in sleep patterns among older people. Bernadette Hood et al, 2004, found that the management of insomnia was improved if elderly people were generally more active and had more exposure to natural light.
(-AO3) Limitation of describing the SFN as the ‘master clock’
There are numerous circadian rhythms in many organs and cells – not just the SCN. Research has shown that feeding mice in specific patterns was shown to alter circadian rhythms for up to 12 hours. Rhythm of SCN was unaffected. Suggests there are more complex influences on sleep-wake cycle.
(-AO3)Influence of exogenous zeitgebers on sleep-wake cycle may be overstated/deterministic
Individuals living in the arctic (the sun doesn’t set in the summer) and somehow maintain normal sleep patterns. Suggest exogenous zeitgebers can have no influence in specific circumstances. More influences in cycles need to be considered. And changing light levels didn’t necessarily lead to abnormal patterns.
(-AO3) Interactionist approach may be more appropriate when identifying influences on the sleep-wake cycle
Research tends to only look at the influence of exogenous zeitgebers or endogenous pacemakers. Therefore, lacks external validity because the two clearly interact to determine sleep-wake patterns. E.g., Siffre only investigated endogenous pacemakers and ignored exogenous zeitgiebers.
