Biopsychology - endogenous pacemakers and exogenous zeitgebers Flashcards
1
Q
what is the primary endogenous pacemaker in humans?
A
the SCN
2
Q
where is the SCN located?
A
hypothalamus, right above optic chiasm which is responsible for light detection
3
Q
what is the purpose of the SCN?
A
maintains circadian rhythms
4
Q
what are the main exogenous zeitgebers?
A
sound, light and social cues
5
Q
what is an exogenous zeitgeber?
A
external factors that reset biological clocks through entrainment
6
Q
evidence for the role of SCN?
A
- Ralph et al (1990). bred mutant hamsters with 20 hr sleep/wake cycles. transplanted SCN from mutants to normal hamsters and they adopted the 20hr cycle. shows the SCN determines the length of the sleep/wake cycle.
- Decoursey et al (2000). destroyed the SCN in 30 chipmunks. released back into habitat and observed. destroyed cycle and so most were killed by predators. supports SCN’s role as EP.
7
Q
evidence for the role of light as an exogenous zeitgeber
A
- Campbell and Murphy (1998). 15 pts woken at different times in the night and shone a light behind their knee. disrupted sleep/wake cycle with variation of up to 3 hrs. shows skin cells can detect light, not just the eyes. suggesting the sleep/wake cycle is a combination of both EP’s and EZ’s.
8
Q
strengths of research into EP’s and EZ’s
A
+ practical applications - more understanding and more treatments for cycle difficulties
+ lots of supporting evidence
9
Q
limitations of research into EP’s and EZ’s.
A
- difficult to isolate EP. in everyday life EP’s and EZ’s interact so attempting to isolate can lower external validity of research
- EZ’s don’t have same impact in all environments. Inuits in Arctic circle with 6 months of darkness still have around 24 hour sleep/wake cycle. SWC mostly controlled by EP’s
- evidence challenging EZ’s. Miles et al, studied blind man with 25 hr SWC. could not be changed despite exposure to social cues, showing they alone are not effective in resetting biological rhythms.
