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PSYA3 - Endogenous pacemakers and Exogenous zeitgebers

  • Essay length: 485 words
  • Submitted: 25/06/2010
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AS and A Level Physiological Psychology

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DISCUSS THE ROLE OF ENDOGENOUS PACEMAKERS AND EXOGENOUS ZEITGEBERS IN THE SLEEP-WAKING CYCLE AND AT LEAST ONE OTHER BIOLOGICAL RHYTHM (25 marks)

The sleep-wake cycle is an example of a circadian rhythm. These are rhythms that last for 24 hours. The circadian rhythm may be controlled by endogenous pacemakers (internal innate mechanisms such as the suprachiasmatic nucleus) or/and exogenous zeitgebers (external factors such as the light/dark cycle)

A case study of a man who was blind from birth found that he had a 25 hour sleep/wake cycle despite exposure to clocks and radios that acted at time cues. He had to take tranquillisers in order to synchronise his cycle with the rest of the world. This suggests that light, an exogenous zeitgeber, is the dominant time cue. Siffre spent six months in a cave. He had artificial light and could ask for the lights to be put off when he wanted to sleep and put on when he woke up. His sleep-wake cycle extended to about 25 hours. This shows we use the exogenous zeitgeber light to synchronise our sleep-wake cycle to 24 hours, the natural cycle of day and night.

A natural study into

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