Circadian Rhythms Flashcards
1
Q
Why does the brain need sleep ?
A
- Lack of sufficient sleep, the part of the brain that controls language, memory, planning and sense of time is severely affected, practically shutting down.
- Sleep-deprived individuals often have difficulty in responding to rapidly changing situations and making rational judgements.
2
Q
What are Circadian rhythms ?
A
- Comes from circa (about) and diem (day) means “about a day”
- Cycle which repeats every 24 hours.
- Big question is whether these rhythms are endogenous – occurring naturally – or exogenous – dependent on external cues like light.
3
Q
What evidence is there for endogenous (internal) processes ?
A
- In plants in 1729 when Jean-Jacques d’Ortous de Mairan kept mimosa plants in the dark
- Found the leaves opened in the morning and closed in the evening even without sunlight.
- In 1972, Michel Siffre lived in a cave 400ft below the surface for two months.
- It was found his body followed a daily sleep cycle. -Although it was 24 and a half hours, rather than 24
- This suggests humans have a natural internal body clock.
4
Q
What evidence is there for external (exogenous) processes ?
A
- Light does appears to be crucial in maintaining the 24 hour circadian rhythm.
- Campbell and Murphy (1998) shone bright lights on to the back of participants’ knees
- Were able to alter their circadian rhythms in line with the light exposure.
- Possible that blood chemistry was altered and this was detected by the SCN
- However, social factors reset rhythms, rather than light levels in the Arctic Circle where it is light for six months of the year, but people still sleep for seven hours on average.
5
Q
How do circadian rhythms work ?
A
- Body temperature changes, peaks at mid-afternoon around 37.1C and troughs in the early hours at 36.7C.
- In non-humans the pineal gland is the brain structure responsible for maintaining circadian rhythms.
- In humans the suprachiasmatic nucleus (SCN) appears to control the sleep/wake cycle.
- It is in the hypothalamus and receives information about light levels through the optic nerve.
- The SCN seems to be the location of our main body clock.
6
Q
What situations are there where our internal clocks come into conflict with external cues ?
A
- Conflict with external cues like light/dark.
- Jet lag – when we travel across timezones
- Shift work – where we operate on a rotating schedule of hours.
7
Q
How does Shift work interfere with our rhythms ?
A
- Results in fatigue, sleep disturbance, digestive problems, lack of concentration, memory loss and mood swings.
- Compounded by people reverting to normal sleep patterns on days off and shift patterns altering from one week to the next.
- Means people’s biorhythms are in a permanent state of desynchronization.
8
Q
What are the problems with Shift work affecting our rhythms ?
A
- People never adapt to a new rhythm, leaving their biorhythms permanently desynchronised.
- Can result in reduced productivity and risks to their health – such as heart disease, digestive disorders and regular tiredness.
9
Q
How do rotating shifts affect our rhythms ?
A
- Rotating shifts involve working different hours each week or month.
- Cooper (2005) looked at oil rig workers and found those on split shifts never fully synchronised.
- Tests showed higher levels of circulating fatty acids putting them at risk of CHD and hypertension.
- Shifts can rotate clockwise or anticlockwise.
- A rotating shift pattern can lead to permanent desynchronization.
- Most research suggests a clockwise pattern is better – but there is disagreement over the speed of rotation.
- Bambra (2008) say a much faster rotation of three to four days is better so the body never has time to adjust to the new cycle.
10
Q
What was the design of Czeisler’s study ?
A
-Field experiment
-Matched group design of participants with comparable jobs.
-85 male rotating shift workers, aged 19 to 68
Control group of 68 male non-rotating day and swing shift workers, with comparable jobs aged 19 to 56 (mean age 27.3)
-All were selected from the Great Salt Lake Minerals and Chemicals corporation in Utah, USA.
11
Q
What was the procedure of Czeisler’s study ?
A
- Self reports conducted
- Rotating shifts noted more insomnia
- 29% of rotators reported falling asleep at work
- 90% complained of schedule changes
- Given presentation on adjusting to sleep and work
12
Q
How were the participants divided in the key study ?
A
- 85 shift workers divided into two groups – and on to a phase delay (clockwise) instead of a phase advance (anticlockwise) schedule.
- 33 of them continued to rotate every seven days, and the remaining 52 moved on to a 21-day change.
- Each worker was given self reports on health measures, sleepiness and schedule preference.
- Staff turnover and plant productivity were analysed nine months after implementing the new schedule.
13
Q
What were the results of Czeisler’s study ?
A
- Workers preferred the phase-delay (clockwise) shift.
- Complaints that the schedule changed too often dropped to 20% among workers on the 21 day rotation – and they were significantly more satisfied with their schedule than those on the seven-day rotation.
- They also reported significantly increased scores on a health index.
- Nine months later staff turnover was the same as those on fixed shifts and there was an increase in productivity.
14
Q
What was concluded from Czeisler’s Study ?
A
- Work schedules that rotate by phase delay with an extended interval between each rotation are most compatible with the properties of the human circadian rhythm.
- However any new schedule must take into consideration the nature of work and the needs of workers.
15
Q
How can be Schedule changes be used to tackle shift work ?
A
- Workers have the same shifts with no rotation – although this causes problems for permanent night shift workers on days off. Also it could be hard to find and keep staff.
- Rapidly rotating shifts – such as two days, two nights, four days off with 12-hour shifts. This can improve total sleep length and leisure activities, improve blood pressure and reduce the use of stimulants.
- Giving shifts to those with greatest tolerance for abnormal schedules or allow people to choose shifts. This has been shown to increase job satisfaction and work-life balance.
- Caution though – studies tend to be on one type of workplace. Can they be generalised?
