Discuss the role of endogenous pacemakers in the control of one or more circadian rhythms (8 + 16 marks)

Endogenous pacemakers are the internal biological clocks that manage our rhythms. In humans, the main biological clock is the suprachiasmatic nucleus also referred to as the SCN which is a small cluster of neurons located in the hypothalamus in the brain. This is what controls circadian rhythms of sleep- waking, body temperature and feeding patterns, the SNC is located above the optic chiasm therefore when light hits the retina it transfers through the optic nerve to the SCN which stimulates the release of hormones such as cortisol and melatonin in the pineal gland, maintaining our sleep- wake cycle.

It’s been suggested from a evolutionary psychologists that endogenous pacemakers have an adaptive value in controlling biological rhythms such as the sleep- wake cycle, therefore suggesting it aids survival. This idea is supported by studies from psychologists such as Decoursey who found that removing the SCN in 30 chipmunks and returning them to their natural habitat, proved costly for their survival. They found that after 80 days significantly more chipmunks had died compared to control group with normal functioning SCN’s. Therefore, this suggests that EP, most importantly the SCN, indeed aids survival, as the absence of this important EP proved detrimental for the survival of the chipmunks.

Moreover, another study that supports this idea is the study of free running biological rhythms by Michel Siffre. This was shown as Siffre spent 179 days deep in a cave in Texas, as a result separated from the influence of natural exogenous zeitgebers such as light. He could ask the researchers above ground for the artificial lights to be turned off when he wanted to sleep, and to be turned on when he woke up. They also monitored various physiological functions such