biological rhythms Flashcards
(21 cards)
biological rhythms are governed by what two things
endogenous pacemakers which control the internal rhythms and exogenous zeitgebers which are external factors such as light
list and define the 4 biological rhythms
circadian rhythms - once in 24 hours
ultradian rhythms - multiple times during 24 hours
infradian rhythms - longer than 24 hours
circannual rhythms - every year like the seasons
describe how the circadian rhythm of the sleep-wake cycle uses light as an exogenous zetigeber
light is the primary input and external cue for sleeping and waking. it is detected by the eye, which sends messages concerning the level of brightness to the suprachiasmatic nuclei (scn). the scn uses this info to coordinate the activity of the entire circadian system
what was michel siffre’s experiment and what did he find
he found that the absence of external cues significantly altered his circadian rhythm. when he returned from a stay in an underground cave with no clocks or light he believed the date to be a month later than it was. this is because he believed one day was longer than it was and his 24 hour sleep wake cycle was increased by the lack of external cues.
what was ashoff and wever’s wwii bunker study and what did they find
deprived of natural light, all but one participant displayed a circadian rhythm between 24 and 25 hours. this suggests that our natural rhythm is slightly longer than 24 hours but we shorten it due to exogenous zeitgebers such as daylight and meal times.
how is practical application to desynchronization a strength of circadian rhythms
informed researchers of when it is disruptive. night workers experience a period of reduced concentration around 6am called a circadian trough, meaning mistakes and accidents are more likely to occur. research has also shown links between shift work and poor health, leading to heart disease due to the stress of adjusting to different sleep/wake patterns
how is practical application to drugs a strength of circadian rhythms
circadian rhythms coordinate basic processes such as heart rate, digestion and hormone levels. this has an effect on how well drugs are absorbed, as research shows that certain times of day make drugs more effective. this has led to the development of guidelines to do with the timing of drug dosing for medications (baraldo)
how is generalisability a weakness of circadian rhythms
tend to involve small groups or single individuals. aged 60 siffre found that his internal clock was slower than when he was younger, showing that even with the same person involved there are factors that vary
what are the stages of the sleep stages in the ultradian rhythm
90 minute intervals, also during the day as part of the basic rest activity cycle (brac). alternates between rem and non-rem sleep with five stages. light sleep, deep sleep and rem sleep (where brain waves speed up and dreaming occurs). this then repeats itself
what has research using eeg shown about the stages of sleep
distinct brain wave patterns. light sleep stages produce alpha waves progressing to theta waves. deep sleep stages produce slower delta waves
how is tucker et al’s individual differences a weakness of ultradian rhythms
difficult to investigate patterns. tucker et al found significant differences between ps in terms of the duration of each stage, particularly just before rem sleep. this means there may be innate differences in ultradian rhythms
how is the case study of randy gardener a weakness of ultradian rhythms
indicates the flexibility of ultradian rhythms. gardener remained awake for 264 hours, experiencing blurred vision and disorganised speech but coping rather well with the massive sleep loss. after this randy slept for just 15 hours and only recovered 25% of his lost sleep. he recovered 70% of deep sleep and 50% of rem sleep, and very little of other stages. this shows the large degree of flexibility in the sleep cycle and its variable nature
what is an example of an infradian rhythm
the female menstrual cycle which is regulated by hormones that either promote ovulation or stimulate the uterus for fertilisation
when does ovulation occur
roughly halfway through the cycle when oestrogen levels are at their highest and usually lasts for 16-32 hours.
what happens after the ovulatory phase
progesterone levels increase in preparation for a possible implantation of an embryo in the uterus
describe the variation of menstrual cycles
the usual cycle is around 28 days however some experience a short cycle of 23 days while others experience longer cycles of 36 days.
how is seasonal affective disorder an example of an infradian rhythm
people become depressed in the winter because they lack melatonin which is secreted by the pineal gland during the night. the lack of light during winter results in a longer period of melatonin secretion which has been linked to the depressive symptoms
how is reinberg’s study a discussion point for the menstrual cycle
suggests its also governed by exogenous zeitgebers. reinberg examined a woman who spent three months in a cave with only a small lamp. it was found that her cycle shortened from 28 days to 25.7 days, suggesting that the lack of light in the cave affected her menstrual cycle.
how is russell et al’s study a weakness of menstrual cycles
found that cycles become synchronised through odour exposure. sweat samples from one group were rubbed onto the upper lip of another group. despite them being separate it was found that the groups cycles synchronised, suggesting its affected by pheromones. this indicates that external factors must be taken into consideration and perhaps a more holistic rather than reductionist approach should be taken
what do evolutionary psychologists suggest about synchronised menstrual cycles
provides an evolutionary advantage as it means that pregnancies can be synchronised and childcare can be shared among multiple mothers who give birth at the same time.
how is terman a discussion point for seasonal affective disorder
found that sad is more common in northern countries where the winter nights are longer. terman found that sad affects 10% of people in new hampshire and only 2% in southern flordia. suggests that sad is affected by light that results in increased levels of melatonin
