AQA A2 Biological Rhythms
- Created by: Georgina Aldis
- Created on: 27-11-13 20:10
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- Biological Rhythms
- Circadian Rhythms
- Last 24 hours. Eg Sleep/Wake Cycle
- Michel Siffre; Spent 6 months in a cave with no zeitgebers. Pacemakers regulated body however, internal clock extended to 25 hours.
- Last 24 hours. Eg Sleep/Wake Cycle
- Infradian Rhythms
- Lasts more than 24 hours. Eg, Menstrual Cycle
- Reinburg found that women's menstrual cycles synchonise to one another due to pheromones which are released into the air
- Under control of endogenous pacemakers and exogenous zeitgebers
- Endogenous Pacemakers - hormones, particularly oestrogen and progesterone
- Exogenous Zeitgebers - women's cycles can synchronise
- Reinburg found that women's menstrual cycles synchonise to one another due to pheromones which are released into the air
- Evolutionary advantage - synchronisation meant women would give birth at the same time; this would allow them to share breast feeding
- Lasts more than 24 hours. Eg, Menstrual Cycle
- Ultradian Rhythms
- Last less than 24 hours. Eg Sleep Stages
- Dement and Kleitman found 70% of pps woken during REM sleep reported dreaming
- Last less than 24 hours. Eg Sleep Stages
- Regulated by Internal & External Factors
- Internal - Endogenous Pacemakers
- The main one being the SCN - a small group of cells in the hypothalmus located behind the eyes
- It is sensitive to light & regulates the pineal gland which secretes melatonin
- Morgan - removed the SCN of hamsters & found the circadian rhythm disappeared
- Silver - transplanted SCN cells back into the hamsters & found the rhythm re-established
- The main one being the SCN - a small group of cells in the hypothalmus located behind the eyes
- External - Exogenous Zeitgebers
- Light is the main one as it resets the SCN & other oscilators
- Siffre - no clocks and no natural light --> sleep wake cycle extended to 25 hours
- Internal - Endogenous Pacemakers
- Disrupting Biological Rhythms. Eg Shift Work and Jet Lag
- Genome Lag Theory - our genes have not kept pace with the changes in our environment
- Shift work involves regular changes to the hours of work. It allows organisations to work around the clock
- Coren found our average night's sleep is 1.5 hours shorter than 100 years ago
- Effects
- Sleep Deprivation - harder to sleep during the day.
- Tilley & Wilkinson; daytime sleep is 2hrs shorter. REM is affected
- Depression - disruption of family and social life
- Solomon; divorce rates are 60% higher in shift workers
- Effects on health
- Knuttson et al; individuals that shift work for longer than 15 years were 3 times more likely to develop heart disease
- Sleep Deprivation - harder to sleep during the day.
- Boivin; nightworkers experience a circadian trough when their cortisol levels are lowest between midnight and 4am
- Jet lag is caused by the body's internal clock being out of step with external cues
- Phase delay; E-->W. Day is lengthened; have to delay sleep time to adjust (easier)
- Phase advnace; W-->E. Day is shortened; have to advnace body clock to catch up (harder)
- Effects
- Performance Decrement
- Recht, Lew & Schwartz; US baseball teams over 3 year period. Found teams traveling E-W before a game won 44% of games, those traveling W-E won only 37%
- Long Term Health Effects - Women
- Female flight attendants often find their menstrual cycles stop & can find it increasingly difficult to get pregnant
- Performance Decrement
- Circadian Rhythms
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