Biological rhythms

• Endogenous pace makers are internal clocks. They are liked to the sleep wake cycle and hunger and thirst. They are linked with superchiasmatic nucleus which is linked to the pineal gland.
• Exogenous zeitgebers are external cues. Light is a big one relation to the secretion of melatonin from the pineal gland. The can be things like social cues, eg meal times
• Russel et al studied periods becoming synchronised, due to pheromone exposure. Upper lip, sweat. This supports the fact that inf. is affected by exogenous zeitgebers.
• Turke, found a evolutionary benefit to syncing periods. Sharing child duties.
• Light sends a message to the superchiasmatic nuclei which uses the information to coordinate activity of circadian rhythm. Sleep wake is also effected by homoeostasis, in terms on energy consumption.
• Body temperature is another circadian rhythm, at its lowest at around 4:30am and highest around 6pm
• There is research support for circadian rhythms. Siffre found that the absence of external ques significantly altered circadian rhythm. However, Siffre was the sole participant in the study so it was subject to lack of generalisability and investigator effects.
• There are individual differences to circadian rhythms. Innate differences that may deem people morning, or evening people (found by Duffy). Researchers must take this into account when investigating.
• There has been criticism that temperature is more of an influence than light on circadian rhythms. Research has found that fluctuations in temp can cause tissues and organs to become inactive or active.
• An example of a infradian rhythm is seasonal affective disorder
• Research suggest that inf. is governed by exogenous zeitgebers. Reinburg examined a woman who lived in a cave for 3 months, with only a small lamp. Her menstrual cycle shortened by 2 days.
• A limitation of Reinberg's study is that there were no controls, meaning we cannot be sure if her period would have changed anyway due to other factors such as dietary changes.
• There is research to support that inf. are important regulators of behaviour. Research found that women found feminine faces more attractive at least fertile, and masculine faces at more fertile.
• EEG has highlighted sleep cycles. Stages 1 and 2 are light sleep, and have slower brainwave patterns. Stages 3 and 4 are deep sleep and have even slower delta waves. Stage 5 is REM sleep, brain waves emulate an awake person.
• Research has found that sleep cycles are effected by individual differences. They found variations in duration of stage 3 and 4 . However, this research was carried out in a lab meaning sleep patterns may not be representative of real life.
• Ult. is flexible. Gardiner stayed awake for 264 hours. He had blurred vision and disorganised speech, but overall coped rather well. When he finally slept, he recovered 70% of his stage 4 and 50% of his REM.