Endogenous pacemakers and exogenous zeitgebers Flashcards
The SCN
Is the main endogenous pacemaker that lies within the hypothalamus. The SCN sends signals to the pineal gland directing it to increase the production of melatonin at night. Melatonin induces sleep.
Support for endogenous pacemakers having an adaptive advantage
Chipmunks had their SCN removed and returned them to their natural habitat. After 80 days, a significant amount of the chipmunks had been killed, this was due to them being awake at night and making noise and so the weasels could hear them and killed them.
Light as the dominant zeitgeber
Changing a blind man’s rhythm from 25hrs to 24hrs proved to be hard which stresses the importance of light as exogenous zeitgeber.
Social cues
Some argue social cues are just as important zeitgebers as in some countries it is always light, but going to work and eating keeps their rhythms regular as light doesn’t change.
Evaluation
the role of the SCN
bred ‘mutant’ hamsters so they had circadian rhythms of 20hrs rather than 24hrs. They transplanted their SCN’s into normal hamsters and the normal hamsters showed the rhythms of the mutant hamsters.
Evaluation
What is the research for the rhythms we have being separate to each other?
Kate spend time in a cave and when finished, her temperature rhythm was 24 hrs but her sleep was a 30hr rhythm, showing support for separate biological rhythms.
Evaluation
Does artificial lighting have an effect on circadian rhythms?
It has been shown that rhythms can be changed by shining light on the back of someone’s knees. Artificial light does have an effect. Disruptions to circadian rhythms means disruption to melatonin production which might explain why some women in industrilaised societies are more likely to develop breast cancer.
Evaluation
Non human research
Much of this research cannot be generalised due to it being done on animals or from case studies and so cannot apply to everyone.
