Biopsych: EPs And EZs Flashcards
What’s the main EP?
the SCN, but peripheral pacemakers include: skin, adrenal gland, liver, lungs, pancreas, spleen.
What’s the main EZs?
light, but other zeitgebers include: social cues (mealtime), temperature changes, clocks, physical activity, food availability (in animals)
What does Siffres study show about pacemakers?
that pacemakers are influential in controlling circadian rhythms - his sleep/wake cycle stayed relatively close to 24 hours in the absence of zeitgebers. It also shows that zeitgebers ‘reset’ the circadian rhythm as his rhythm did extend slightly beyond 24 hours. — however Siffres study has some issues.
What did McClinktocks study show about EPs
The women in McClintocks study had periods influenced by endogenous pacemakers. But their cycle was affected by exogenous zeitgebers - another women’s pheromones. However this study also has some issues.
What did Stephan and Zucker find that supports EPs?
investigated effects of damage to SCN on circadian rhythms. Rats were housed in labs with 12 hours of light followed by 12 hours of dark- show a rhythm of drinking and locomotor activity (more during the dark). Damage to the SCN eliminated normal patterns of activity. Concluded SCN = key pacemaker in brain controlling circadian rhythms.
What did Ralph and Morgan find about mutant hamsters?
If ‘mutant’ hamsters are bred so that they have a circadian rhythm of 20 instead of 24 hours and their SCN are transported into normal hamsters, then normal hamsters display the mutant rhythms.
What did DeCoursey et al find about chipmunks
They destroyed the SCN in some chipmunks and found these animals were much more likely to be active at night than normal chipmunks, and more likely to be taken by nocturnal predators.
Who also support the idea EPs are important?
Aschoff and Weber, and Siffre
How did Blinkley support EZs?
chickens are very responsible to light levels and will wake at first light due to info going to the pineal gland from the eye. Cover the eye with a little hat and chickens will not wake at dawn.
What did Miles find that supports EZs?
The importance of light as a time giver can be seen in the difficulties observed in blind people and their sleep patterns. One man, who was blind from birth had a circadian rhythm of 24.9 hours. He was exposed to various exogenous cues, but could not regulate his internal pace. He had to take stimulants in the morning and sedatives at night in order to set his rhythms with the rest of the world
What did Czeisler find about EZ?
found that some people who are blind do respond to exposure to very bright light with reduced melatonin levels, just like normally sighted people. Suggests there are two pathways to the brain from the eyes, one for the conscious vision and other for light travelling.
What did Campbell and Murphy find supporting EZs?
found shining a light on the back of ptps knees shifted their circadian rhythms by upto 3 hours in some cases.
Why might the SCN may not be the only pacemaker?
The SCN appears to be the master clock, but body temp rhythm persists when both SCNs are removed, which suggests there is another one- possibly near the SCN in the ventromedial hypothalamus.
What did Kate Aldcroft find about the SCN not being the only pacemaker?
Kate Aldcroft (1996) spent weeks in a cave. After 25 days, her temperature adopted a 24 hour rhythm, yet her sleep rhythm altered to a 30 hour cycle.
What are some other issues of EP and EZs?
- Methodological issues - zeitgebers do not have the same effect in all environments (people in the Artic Circle have similar sleep patterns all year round - despite 6 months in complete darkness) - primarily controlled by endogenous pacemakers.
- Interactionist system - in everyday life, pacemakers and zeitgebers interact and work together, so makes little sense to always separate them. The more attempts to isolate the influence of internal pacemakers, etc, the lower the validity
