provides an in-depth summary of all A01 sections, with reference to relevant research pieces needed. Also provides an outline of all evaluation points for each section to be able to use in questions needing A03
Biological rhythms: circadian rhythms Biological rhythms: infradian and Endogenous pacemakers, exogenous
Biological rhythms are periodic activity ultradian zeitgebers
governed by: Infradian rhythm: more than 24 hours to Endogenous pacemakers and sleep/wake cycle:
- Internal biological clocks complete SCN: the suprachiamatic nucleus is a tiny
- External changes in the environment The female menstrual cycle is about 28 days so bundle of nerve cells in the hypothalamus
Circadian rhythms: about one cycle every 24 an infradian rhythm. Exogenous zeitgebers which helps maintain circadian rhythms, nerve
hours, like sleep/wake cycle may synchronise menstrual cycles: Stern and fibres from the eye cross at the optic chiasm on
Sleep/wake cycle is governed by internal and McClintock studied 29 women with irregular their way to the right and left visual areas. The
external mechanisms periods, pheromones were taken from some at SCN lies just above this and receives info about
- Exogenous zeitgebers: feel drowsy at different stages in their cycles via cotton pad, light from this
night, alert at day shows effect of cotton pad was cleaning with alcohol ad later DeCoursey destroyed SCN connections in the
daylight rubbed on upper lip of other pps. 68% of brains of 30 chipmunks which were returned to
- Endogenous pacemakers: a bio clock women experienced changes to their cycle their natural habitat and observed for 80 days.
‘left to its own devices’ without influence
which brought them closer to cycle of the Their sleep/wake cycle disappeared and many
of external stimuli ‘odour donor’ illed by predators
- The basic rhythms is governed by the SAD (seasonal affective disorder) is a The SCN passes information on day length to
superchiasmatic nucleus which provides depressive disorder with seasonal pattern, the pineal gland which increases production of
info from eyes about light often during winter when daylight hours melatonin during the night. Melatonin is a
Siffre cave study: he spent long periods in dark decrease hormone that induces sleep and is inhibited
caves to examine effects of free-running - During the night the pineal gland during periods of wakefulness
biological rhythms, two months (1962), 6 secretes melatonin until dawn when Exogenous zeitgebers and sleep/wake cycle:
months (1970s) there is increase in light, in winter less External environmental factors that reset
- his free-running circadian rhythm settled light means melatonin secretion goes on biological clocks: resetting bio clocks is known
at 25 hours in both for longer so knock-on effect on as entrainment
- he had a regular sleep/wake cycle production of serotonin in the brain Without external cues, the free-running bio
Aschoff and Wever: group of pps spent 4 weeks Ultradian rhythm: less than 24 hours, occur clock continues to tick in cyclical pattern.
at ww2 bunker deprived of natural light, all but many times a day Zeitgebers reset the sleep/wake cycle
1 had circadian rhythm between 24 and 25 Sleep pattern occurs in 90-minute periods, Light is a key exogenous zeitgeber that
hours divided into 5 stages, each characterised by a influences sleep/wake cycle
different level of brain wave activity - Light can reset bodys main endogenous
P – application to shift work Stage 1 and 2: light sleep, person may be pacemaker and also has an indirect
E – shift work creates desynchronisation of bio easily woken, brain waves are high, called influence on key processes in controlling
rhythms. Boivin found shift workers experience alpha waves hormone secretion, blood circulation etc
a lapse of concentration at around 6am Stage 3 and 4: deep sleep or slow wave sleep, Campbell and murphy: woke 15 pps at various
(circadian trough) so accidents are likely individual waves now have lower frequency and times and shone a light on backs of peoples
E – research also suggests link between shift higher amplitude. Difficult to wake person knees producing a deviation in sleep/wake
work and poor health, shift workers are more Stage 5: REM sleep, body is paralysed yet brain cycle of up to 3 hours. Light does not
likely to develop heart disease activity closely resembles that of awake brain, necessarily rely on the eyes to influence the
L – research into sleep/wake cycle may have brain produces theta waves and eyes move SCN
economic implications I terms of how best to around Social cues also have important effect: babies
manage shift work are entrained by 16 weeks with schedules
CA – research is correlational, therefore P – real world application imposed by parents including adult determined
desynchronisation may not be the cause of E – light therapy reduces debilitating effects of mealtimes.
observed difficulties. Solomon concluded that SAD in 80% of people
high divorce rates in shift workers might be due E – however rohan recorded 46% relapse rate P – endogenous pacemakers cannot be studies
over successive winters compared to 27% in a in isolation
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