biological rhythms- biopsychology Flashcards
what are biological rhythms
everything subject to them
exert important unfluence on way in which body systems behave
governed by two things- bodys internal biological clocks (endogenous pacemakers) and external changes in environment (exogenous zeitgebers)
may occur during the day (ultradian rhythms) others take longer than a day to complete (infradian rhythms) and sometimes much longer (circannual rhythms)
circadian rhythms last 24 hours- sleep wake cycle and core body temp
what is the sleep wake cycle
feel drowsy when night time and alert during day demonstrates effect of daylight- exogenous zeitgeber
governed by internal pacemaker- biological clock called suprachiasmatic nucleus
scn lies above optic chiasm which provides info from eye about light
exogenous zeitgebers can rest scn
researchers tried answering if we had no idea whether it was ngight or day would we still fall asleep and wake up at regular times
what is suffres cave study
siffre self styled caveman spent extended periods underground study effects on own biological rhythms
deprived f exposure to natural light and sound but with access to adequate food and drink, resurfaced mid sept 1962 after 2 months in caves of southern apls believe it to be mid august
decade later performed similar feat but this time for six months in texan cave
free running biological rhythm settled down to one that was beyond usual 24 hours though he did continue to fall asleep and wake up on regular schedule
what was other research
aschoff and wever concinved group of pps to spend 4 weeks in world war 2 bunker depvied of natural light
all but one pps whos sleep wake schedule extended to 29 hours displayed circadian rhythm between 24 and 25 hours
natural sleep wake schedule may be slightly longer than 24 hour day
not overestimate the influence of exogenous zeitgebers on internal biological clock
folkard studied group of 12 people agreed to live in dark cave for 3 weeks retiring to bed when clock said 1145 and rising 745
researchers gradually speeded up clock so an apparent 24 hour day lasted 22 hours
revealed only 1 pps able to comfortably adjust to new regime
suggest existence of strong free running circadian rhythm that cant be easily overridden by exogenous zeitgebers
what is shift work
provides understanding advere consequences occur when disrupted
night workers engaged in shift work experience period of reduced concentration around 6am meaning mistakes and accidents more likley
research pointed to relationship between shift work and poor health- 3 times more likely to develop heart disease than people who work typical work patterns
research into sleep wake cycle may have real world economic implications in terms of how best to manage worker productivity
studies investigating effects of shift work tend to use correlational methods
difficult estbalish whether desynchronisation of sleep wake cycle cause of negative effects
may be other factors
soloman concluded that high divorce rates in shift workers might be due to train of deprived sleep and other influences such as missing out on important family events
suggests may not be biological factors create adverse conseuwences associated with shift work
what is medical treatment
been used to improve medical treatments
circadian rhythms coordinate number of bodys basic processes such as heart rate digestion and hormone level- rise and fall during course of day which has led to field of chronotherapeutics- how medical treatment can be administered in way that corresponds to persons biological rhythms
asprin as treatment for heart attacks is most effective taken last thing at night aspirin reduces blood platelet activity and can reduce risk of heart attack
heart attcks most likely to occur early in morning so timing of taking aspirin matters- research supported
shows research help increae effectiveness of drug treatments
what are individual differences
generalisations are difficult to make
studies described are based on small samples
sleep wake cycles may vary widely from person to person
czeisler found invidual differences in sleep wake cycles varying from 13 to 65 hours
duffy revealed some people have natural preference for going to bed early and rising early whereas other people prefer opposite
siffre 1999 study observed that his own sleep wake cycle slowed down since young man
means difficult to use research data to discuss anything more than averages which may be meaingless
what is the menstrual cycle
example of infradian rhythm
governed by monthly changes in hormone levels which regulate ovulation
cycle refers to the time between the first day of period when womd lining is shed to day before next period
typical cycle takes 28 days complete
during each cycle rising levels of hormon oestrogen cause ovary to develop egg and release it
after ovulation hormone progesterone helps womb lining grow thicker readying womb for pregnancy
if pregnancy doesnt occur egg is abosrbed into body, womb lining comes away and leaves the body
what is synchorning the menstrual cycle
evidence suggests that it may be influenced by exogenous factors
stern and mcclintock demonstrated how menstrual cycles synchronise as result of influence of pheremones
studied 29 women with history of irregular periods, samples of pheremones gathered from 9 of women at different stages of menstrual cycles via cotton pad placed under arm, pads worn at least 8 hours ensure that pheromones picked up, pads treated with alcohol and froxen to be rubbed on upper lip of other pps , on one day pads from strat of menstrual cycle were applied to all 20 women, on day 2 they were all given pad from second day of cycle and so on
found that 68% women experiences changes to thier cycle which brought them closer to cycle of their odour donor
what is seasonal affective disorder
depressive disorder which has seasonal pattern of onset described and diagnosed as mental disorder in DSM-5
man symptoms persistent low mood general lack of activity and interest in life, referred to as winter blues as symptoms triggered during winter months when number of daylight hours becomes shorter
particular type of infradian rhythm called circannual rhythm as it is subject to yearly cycle
can be classed as circadian rhythm as experience of SAD may be due to disruption of seep wake cycle can be attributed to prolonged periods of daily darkness during winter
hypothesised that the hormone melatonin implicated in cause of SAD, during night pineal gland secretes melatonin until dawn when there is increase in light
during winter lack of light in morning means secretion process continues for longer
thought to have knock on effect on production of serotonin in brain- chemical linked to onset of depressive symptoms
what is ultradian rhythms
identified 5 distinct sleep that span 90mins cycle contrinues throughout course of night
each stages characterised by differnt level of brainwave activity which can be monitered using eeg
stages 1 and 2- light sleep where person may be easily awoken, stage 1 brain waves high frequency and short amptitude aplha waves, stage 2 alpha waves continue but occasional random changes in pattern called sleep spindles
stages 3 and 4- known as deep sleep or slow wave sleep, brain waves are delta waves with lower frequency and high amplitude, difficult to wake someone at this point
stage 5- body paralysed yet brain activity closely resembles that of awake brain, brain produces theta waves and eyes occasionally move around rapid eye moment, dream experienced during REM sleep but may occur in deep sleep
what is evolutionary basis
may be explained by natural selection
synchronisation of menstrual cycle thought to have evolutionary value
distant ancestors may have been advantageous for women to menstruate together and become preg at the same time
social group allow babies who had lost mothers during or after childbirth to have access to breast milk improving chances of survival
synchronisation is adaptive strategy
what is methodological limitations
methodological shortcomings
many factors that may affect change to mestrual cycle including stress changes in diet exercise
may act as confounding variable which means that any supposed pattern of synchronisation is no more than would have been xpected to occur by chance
may explain why other studies failed replicate findings
suggest menstrual synchrony studies flawed
what is improved understanding
improved understanding of age related changes in sleep
sleep scientists observed sws reducs with age
growth hormone mostly produced during sws reduced in older people
cauter resulting sleep deficit may explain various issue in old age such as reduced alertness
increase sws relaxation and medication may be used suggests knowledge has practical values
what is individual differences
signf variation between people
tucker found large diffrences between pps in terms of duration of each sleep stage
tucker suggest that differences likely to be biologically determined
makes difficult describe normal sleep meaningful way
