Circadian Rhythms
- Created by: Hannah Jeffery
- Created on: 07-02-15 13:44
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- Circadian Rhythms
- Stephan and Zucker
- investigated effects of damage to the SCN
- rats placed in a laboratory
- given 12 hours of light followed by 12 hours of dark
- they're nocturnal
- they experimental group are operated on to damage their SCN
- Disrupted their circadian rhythms
- SCN is a major pacemaker
- Disrupted their circadian rhythms
- Methodological issues
- eliminated extraneous variables by damaging other parts of the hypothalamus
- proved that they didnt influence circadian rhythms
- difficult surgical procedure
- only 11 out of 25 rats survived
- severity of the operation may of affected rats behaviour
- difficult to generalise rats to humans
- eg rats are nocturnal
- low population validity
- would need to be confirmed by human studies
- eliminated extraneous variables by damaging other parts of the hypothalamus
- ethical issues
- cause rats stress and harm
- killed animals
- light is the dominant zeitgeber and can reset endogenous pacemakers
- Campbell and murphy found that be shining light on the back of someone's knees the circadian rhythm will be altered
- real life application
- we live in a world were artificial light is very accessible
- stevens says they exposure to artificial light disrupts circadian rhythms
- we live in a world were artificial light is very accessible
- reductionist
- in Finland in the winter 6 hours of daylight in summer
- blind people
- retina unable to pick up light rays
- not influenced by exogenous zeitgeber
- Sack et al found that half of blind people had free running endogenous pacemakers
- tells us that exogenous zeitgebers are important for the natural synchronising of endogenous pacemakers
- time givers can be used to synchronise endogenous zeitgebers
- retina unable to pick up light rays
- sunlight can be compromised
- mechanisms are complex and cannot be diluted to a simple format
- Stephan and Zucker
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