circadian rhythms

Created by

samuel

Cards (7)

circadian rhythms last for 24 hours
e.g. sleep/wake cycle - governed by SCN but entrained by exogenous zeitgebers
e.g. changes in core body temperature - varies from 2 degrees each day, lowest at 4pm, highest at 6pm, the warmer we are the better our cognitive performance
exogenous Zeitgebers can reset the SCN (endogenous pacemaker)
SCN is internal body clock
if left without the influence of EZ then our rhythm is free-running
the sleep/wake cycle is when we feel drowsy during night time and alert during the day and demonstrates EZ and EP influence
sunlight is detected by retinas in the eyes
the eyes send information to the optic chaism
which is then sent to the occipital love via the hypothalamus
which sends the info to the superchiasmatic nucleus (SCN)
then a signal is sent to the pineal gland in the endocrine system
if there is sunlight serotonin and cortisol is secreted
in the absence of sunlight melatonin is secreted
siffre spent several extended periods underground to study the effects of his own biological rhythms
he was deprived of social cues, natural light and sound
he spent 6 months in a texan cave
his 'free-running' circadian rhythm settled to 25 hours and he did continue to fall asleep and wake up on a regular basis
he measured his heart rate and his brain, and blood pressure
suggests that the sleep/wake cycle is biologically determined as endogenous pacemaker is more important, but zeitgebers are needed for entraining
siffre's methodology was scientific as he isolated exogenous zeitgebers to scientifically and empirically test
he took cognitive, psychological measures measures daily e.g. heart rate, blood pressure, EEGs
his objectivity in his data collection provided a comprehensive set of data which validated his conclusions about circadian rhythms
Group of pps spent 4 weeks in a WW2 bunker deprived of natural light and time cues
all pps sleep/wake cycle extended to 25 hours other than one which was 29 hours
supports siffre's research as suggests that our 'natural' cycle is just over 24h but entrained by by EZ such as daylight, mealtimes
However, it also shows that there are individual differences in our SCN and some people may need EZ more than others for synchronisation, so we need to be cautious making conclusions
But pps were also with other people so not entirely deprived from social cues
circadian rhythms can explain why we experience difficulty during night shift, or jet lag -> gives us ways reduce symptoms
nightshift is difficult to adjust to because the pacemaker and EZ will be desynchronised - melatonin will be produced while someone is trying to stay awake and serotonin will be produced when trying to sleep so cognition and alertness will not be at their peak when someone is working -> shift workers get ways to adjust
e.g. sleeping before shift, routine, sleeping in dark room to promote production of melatonin, use bright lights at shift, change meals
understanding our endogenous pacemakers has real-world value for medical treatment and pharmaceuticals
circadian rhythms co-ordinate a number of the body's basic processes e.g. heart rate, digestion and hormone levels
medical treatment can be administered in a way that corresponds to a person's biological rhythms
e.g. aspirin is most effective for heart attacks when taken at night
increases the efficacy as we know what time of day is best for medication based on body temp, digestion, hormones etc