biological rhythms
- Created by: esther christie
- Created on: 04-06-13 15:19
circadian rhythms
Human sleep/wake cycle
- we sleep for 8 hours every 24 hours.
- controlled by endogenous factors (SCN) and exogenous zeitgebers (light)
- 2 months in a cave with artifical light and developed a rhythms of 25 hours - shows there are endogenous pacemakers that effect the rhythm
Human body temperature
- maintained by homeostasis, peaks in the afternoon and troughs in the early morning
- determined by the heat produced and lost in the body
- influenced by external temperature and the SCN
- body temperature was monitored by volunteers in a lab experiment who were woken at different times. a light was shone on their knee which effected the rhythm by up to 3 hours depending on when it was shone. the blood or skin may effect this rhythm
Evaluation- the SCN was removed from hamsters and found that all circadian rhythms disappeared. the rhythms were restablished by transplating SCN cells. mutent cells were also transpanted and gave the hamsters short rhythms
- a blind man had a 24.5 hour cycle that became out of sync, simulants and sedatives were needed, social cues didn't work. light acts as time cue to reset the rhythm
infradian rhythms
human menstral cycle
- controlled by hormones released from the pituitary gland and the ovaries
- FSH and LH are released first which stimulate follicle growth and then oestrogen is released which causes ovulation, progesterone is then released the allow implantation
- underarm sweat was applied to the lips of women which cause their menstral cycle to syncronise, suggesting pheromones are exogenous zeitgebers
hibernation
- exogenous factors are thought to influence the cycle (temperature and food availablility)
- a squirrel was placed in an artifical environment with light for 12 hours and a temperature of 0'c, the animal still hibernated october- april. its body temp dropped in the 300 day cycle. there must be an endogenous factor influencing the squirrel
Evaluation - some evidence has found no correlation between menstrual cycles in a womens basketball team
- a lot of evidence suggesting there's individual differences in peoples infradian rhythms
ultradian rhythms
human sleep cycle
- change from NREM to REM, a whole cycle lasts 90 minutes
- EEG studies have found that the brain has different activity for each stage
- REM - muscles are paralysed but brain activity is similar to when awake
- NREM - brain waves are in patterns
- participants woken during REM reported dreaming 80% of the time, those woken during NREM reported 20% of the time
- biological clock in the pons part of the brain that controlls the cycle, also the same factors that influence the sleep/wake cycle
BRAC (basic rest- activity cycle)
- 90 minutes per cycle
- first half the brain has fast brain waves the individual feels alert, the last 20 mins to brain waves slow down and the individual feels daydreamy
- influenced by lifestyle
Evaluation- a study has found that participants report dreams 70% of the time in NREM - down to dream like thoughts being categorised - observation found a clear eating and drinking patern every 90 minutes for 6 hours
endogenous pacemakers
suprachiasmatic nucleaus (SCN)
- located in the hypothalamus abover the optic nerve
- receives information from light penetrated by the eyelids, and syncs the rhythm with outside
pineal gland and melatonin
- when light levels reduce the SCN sends signals to the pineal gland which releases melatonin hormone which induces sleep by inhibiting brain mechanisms
body clock gene
- PERIOD3 is one clock gene that influence rhythm characteristics, each form of gene has a different circadian pattern, determines whether someones a 'morning person' or not
exogenous zeitgebers
sunlight
- a shift in time zones and light occurs then the rhythms realign to the new cues - entrainment
social cues
- those who live in the arctic circle cannot use light as a exogenous factor so need other cues light social and work habits
disruption of biological rhythms
jet lag
- consequences are tireness, irritability, disorientation and problems concentrating
- happens when travelling east and west
- due to a mismatch of pacemakers set for one time zone and zeitgebers set for a different zone
- it's worse travelling west to east, easier to adjust clocks that are ahead of time because of the natural tendency to lengthen our circadian rhythms
Evaluation - 8 participants travelled between USA and Germany and found adjustment easier for those travelling westbound because of the lengthening of their rhythms
- a lot of individual difference, generalisations cannot be made
- disruption to sleep and hormone patterns led to a cabin crew's cognitive functioning being decreased and mental health problems
disruption of biological rhythms
shift work
- fluctuating shift work - employees continually change shifts causing disruption to eating and sleeping, workers are always desynchronised, which will impair concentration and physical performance and increase stress
- non- fluctuating shift work - employees work consistant night shifts, to workers experience a decrease alertness during a shift around midnight (low cortisol levels) and 4 am (low body temperature). the workers may also experience sleep deprivation because they sleep during the day - up to 2 hours less sleep than nights sleep
Evaluation - nuclear power stations disasters, lorry crashes and oil tanker spills have happened during the night and this could be down to the desynchronising effects of shift work
- 60% divorce rate for night shift workers, could be due to lack of sleep
Related discussions on The Student Room
- A-Level Psychology AQA »
- Aqa psych help »
- AQA Psychology Paper 2 BioPsychology question »
- AQA A-level Psychology Paper 2 (7182/2) - 25th May 2023 [Exam Chat] »
- Rhythm Game EPQ Ideas? »
- Music gcse »
- bayonet charge and exposure comparison essay what mark Is out of 40?? »
- Official Queen's University Belfast freshers 2023 chat »
- music gcse »
- how to modulate from f# major (music gcse) »
Comments
No comments have yet been made