Endogenous pacemakers

Are rhythms that are not imposed by the enviroment but generated from within the organisms
As many biological cycles follow a 24 hour rhythm, even in the absence of external stimuli, there must be an internal biological pacemaker
The main pacemaker is the Super Charismatic nucleus (SCN) a small group of cells in the hypothalamus generating a circadian rhythm reset by light entering the eyes
Role of SCN
1. Morgan (1995) bread hamsters to have 20 hour circadian rhythms instead of 24 (mutants). Transplanted SCN into normal hamsters. Which now show 20 hour circadian rhythm
2. Chipmunks. DeCoursey et al. (2000) removal of SCN in chipmunks led to more deaths. Circadian rhythms disruptive likely that chipmunks more active and detected by predator. Shows importancee adaptive functioning of body clock. issues of ethics and generalisability
Evidence for centeral and pheripheral oscillators
1. Kate Aldcroft. cave study for 25 days, temperature still at 24 hour cycle, but sleep on 30 hour cycle

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	Created by harry_bygraves almost 11 years ago