biological rhythms

• circadian- length of 24 hours- sleep and wake cycle,
• infradian- length- more than 24 hours- female menstrual cycle-
• ultradian- less than 24 hours- the stages of sleep
• biological rhythms are controlled by endogenous pacemakers, which are influenced by exogenous zeitgebers
• endogenous pacemakers- things within the body that regulate biological rhythms ('your body clock'),
• exogenous zeitgebers- cues in the external environment that inform endogenous pacemakers to regulate biological rhythms- eg sunlight and darkness prompt the body to release hormones that control sleep and wake cycles.
• eval of infradian rhythms- Russell et al (1980) found that female menstrual cycles became synchronised with other females through odour exposure. in one study, sweat samples from one group of women were rubbed on to the upper lip of another group. Despite the fact that two groups were separate, their menstrual cycles were synchronised- this suggests that the synchronisation of menstrual cycles can be affected by pheromones (exogenous zeitgeber), which can have an effect on people nearby rather than on the person producing them.
• Ultradian rhythms last fewer than 24 hours, examples include- human meal patterns, sleep patterns,
• ultradian rhythms- light sleep to very deep sleep to REM sleep,
• stages 1 and 2 of light sleep- brain patterns become more slower
• ultradian rhythms research eval- randy gardner remained awake for 264 hours, after this experience, Randy slept for just 15 hours and over several nights he recovered only around 25% of his lost sleep, interestingly, he recovered 70% of his stage 4 sleep, 50% or his REM sleep and very little of the other stages- these results highlight the degree of flexibility in terms of the different stages within the sleep cycle and the variable nature of his ultradian rhythm.
• Tucker et al (ultradian rhythms evaluation points)- found significant differences between participants in terms of the duration of each stage, particularly stages 3 and 4 (just before REM sleep)... This research suggests there may be innate individual differences in ultradian rhythms. which means that it is worth focusing on these differences during investigations into sleep cycles.