Circadian rhythms essay plan.
Introduction AO1
Circadian rhythms are biological cycles that last around 24 hours
There is a free running cycle controlled by an endogenous pacemaker working as a body clock which is internal to our biological system, such as the suprachiasmatic nucleus which receives information about light and dark directly from the retina of the eye and the pineal gland, which releases melatonin in relation to fading light. Melatonin acts upon the raphe nuclei which in turns produces serotonin, a chemical with an inhibitory or slowing down effect on the central nervous system.
Also, circadian rhythms can be controlled by exogenous zeitgebers i.e. external time givers, such as light, temperature and social cues. Another circadian rhythm is body temperature, which is at its lowest at around 4.30 am. The core body temperature also lowers after lunch.
Evaluation AO2
Siffre (1962)- He spent two months in an underground cave, without time cues and emerged on the 27th of September, but he thought it was the 20th of August. This suggests that the absence of exogenous zeitgebers, affected his perception of time, therefore giving evidence that endogenous pacemakers control our circadian rhythms. He then carried out further research to see if the absence of exogenous zeitgebers would affect his sleep- wake cycle. He spent six months in a cave, with no time cues, but artificial lights. He settled into a sleep wake cycle of around 25 hours. This therefore gives reliability and validity to the view that circadian rhythms are set by endogenous pacemakers, and are not dependent on the exogenous cue of light. This research allows us to carry out causal relationship experiments into the importance of endogenous pacemakers.
Unfortunately, Siffre has been the only researcher in his experiments and therefore the evidence to suggest that endogenous pacemakers