Discuss the role of endogenous pacemakers and exogenous zeitgebers in the circadian rhythm. 24 Markers
Circadian rhythm is rhythms that last 24 hours, one day. An example of a Circadian Rhythm is the sleep-wake cycle. Because this rhythm occurs daily, it is tempting to automatically assume that the factors which control it are exogenous zeitgebers, such as natural light patterns, TV, radio, birdsong, Research however has gone into this to find out what exactly controls the circadian rhythms.
Research by Siffer implies that circadian rhythms are controlled by endogenous factors. In 1962 Siffre spent a long period of time living with no daylight, clocks, radios or anything, which could be classified as an exogenous zeitgebers. He had no clues at all for his own personal body clock. For two months, Siffre lived in total isolation, buried 375 feet inside a subterranean glacier in the, with no clocks or daylight to mark time. Inside the cave, temperatures were below freezing. Constantly cold and wet, Siffre suffered from hypothermia, as massive chunks of ice regularly crashed down around his tent. But during his 63 days underground, he only dabbled in madness once. One day, Siffre started singing at the top of his lungs and dancing the twist in his black silk tights. Other than that, he behaved relatively normally. He emerged on the 21st September however he thought that it was in fact the 20th August, this shows he lost track of time. Siffre repeated the experiment in a Texan cave years later. For the first month his circadian cycle stuck to the 24 body clock roughly, however after these early few weeks his sleep-wake cycle went completely and his cycle would range from 18-58 hours. This research is obviously only taken from Siffre himself, the participants aren’t a wide-ranging group. This means it’s hard to apply Siffre’s findings to someone who grew up in a similar setting to himself, never mind a member of a tribe in Mongolia for example. Siffre was...
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