Endogenous Pacemakers Essay

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Describe and evaluate the role of the endogenous pacemakers (25 marks) It is argued that biorhythms such as the release of hormones from the pituitary gland, the daily rise and fall in body temperature and the sleep wake cycle are underpinned by some form of ‘body clock’ situated somewhere in the brain. Psychologists have been attempting to agree upon the extent to which this clock should be seen as a free running mechanism or one which is entrained and regulated by factors such as light and dark and others exogenous zeitgebers or time givers such as social routines of others and man-made clocks. It is thought that one of the body’s most important clocks might be situated in the suprachiasmatic nucleus (SCN), a tiny cluster of nerve cells located within the hypothalamus. This SCN is linked to the optic nerve by a thin tuft of nerve fibres which breaks off just above the optic chiasm and this provides a direct link with light levels in the outside world. This is important as it provides circumstantial evidence that the body clock is regulated by the outside world. It is likely that this…show more content…
He found that when the SCN was leisoned in a sample of chipmunks they were awake when they should be asleep and vice versa. After 80 days, significantly more of the leisoned chipmunks had been killed by weasels. This demonstrated that circadian rhythms may serve an adaptive function to keep the animals still and quiet at dangerous times when they could be attacked by predators. This study had high internal validity and led to evidence which suggested a causal relationship however, it is arguable that this study was unethical as it could have been predicted that many of the animals would die. It should be noted that the process may be far more complex in humans and thus caution should be exercised in generalising these results to
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