Topic 2 - Biological (Biological Rhythms) Flashcards
What are Circadian Rhythms?
Cycles such as body temperature that fluctuate in a specific cycle. For example your temperature rises to a peak in the afternoon and falls to low in the early morning
What is Phase Delay?
Holding back sleep
Sleeping after you are ready to sleep
What is Phase Advance?
Bringing forward sleep
Sleeping before you are ready to sleep
What was the aim of Czeisler et Al’s study?
To investigate effects of taking into account circadian rhythms when designing work schedules
In particular the direction in which shifts are rotated and intervals between rotating these shifts
What was Czeisler et al sample?
85 rotating shift workers
68 non rotating shift workers
Working at a potash factory in Utah,USA
All male
Aged 19-68
153 participants in total
On a phase advance schedule
What were the procedure of Czeisler et Al’s study?
Self report measures were conducted
Czeisler then:
Divided 85 workers on rotating shifts into 2 groups
Moved both groups into a phase delay schedule
Group 1 rotated shifts every 7 days
Group 2 rotated shifts every 21 days
After 3 months workers were given a questionaire about their preferences
After 9 months personnel turnover and plant productivity were analysed
What year was Czeisler et Al’s study?
1982
What year was Czeisler et Al’s study?
1982
What did Czeisler et al find in his initial self report measures.
Those on rotating shifts had more issues with insomnia
29% reported falling asleep at work at least once during the previous 3 months
90% complained their schedules changed too often
80% reported it took 2-4 days for their sleep to adjust after each phase advance
What were the results in Czeisler et al’s study after 3 months?
Significantly more workers preferred the new phase delay schedule over the old phase advance schedule
Complaints that schedules changed too often dropped to 20% in group 2 (originally 90%)
Workers in group 2 were significantly more satisfied with their schedule than those in group 1
They also reported increased scores on a health index
What were the results in Czeisler et al’s study after 9 months?
Staff turnover on the 21 day phase delay schedule was reduced to the same range as a comparable control group of non-rotating shift workers
They was an increased rate of potash harvesting and processed potash production after the introduction of the new 21 day phase delay rotation schedule
What were the conclusions of Czeisler et als study?
Work schedules that use phase delay with an extended interval between each rotation are most compatible with the properties of human circadian timing systems
Explain Siffre’s study:
French scientist Michel Siffre lived in a cave 400ft below the earths surface for 2 months
It was completely dark apart from a light bulb
Siffre was in contact with a team on the surface every time he ate, woke up and when he was going to sleep
He slept when he wanted to & slept as long as he wanted to
His body followed a daily sleep-wake cycle
It was every 24.5 hours instead of 24 hours
Suggests humans have an internal body clock independent of the natural terrestrial day/night
Explain Preckel et al’s study:
Studied German high school children
Children at 5 schools were given a chronotype questionnaire (the lark-owl chronotype indicator) and a standardised cognitive test
Parents of the students also filled in a questionnaire at home rating their child’s chronotype
Found being an owl was a significant negative predictor of overall grade point average (GPA) after cognitive ability was controlled for
What is melatonin and how does it work?
Melatonin is a natural hormone that induces sleep and is inhibited by light
Melatonin is a natural hormone produced as part of the circadian rhythm, more is released when it is dark which signals to the body it is time to sleep, this means if melatonin supplements are taken this can signal to the body to sleep
Melatonin is used to reduce the effects of jet lag
