There are three main biological rhythms, which are called infradian, circadian and ultradian. Ultradian rhythms occur multiple times in one day. Circadian rhythms are cycles, which occur once a day, so within the 24 hours such as the sleep-wake cycle. Infradian rhythms are less frequent once in a day such as the menstrual cycle or hibernation. The research into these rhythms offers an insight into how the body is influenced by exogenous zeitgebers and endogenous pacemakers, but it is still nonetheless unclear what it more influential. An example of circadian rhythms is the sleep-wake cycle that evidence suggests that exogenous pacemakers control it. For example, the theory is that the suprachiasmatic nucleus has an involvement in controlling the sleep-wake cycle….