Disruption to biological rhythms

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There are two main aspects of modern day living that can cause disruption to our biological rhythms.

These aspects are shift work and jet lag.

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Shift work

Shift work is regular changes to the hours of work.

Monk and Folkard found that there are two types of shift work, these are;

  • Rapid changing shifts (weekly)
  • Slow changing shifts (3 weeks)

Rapid changing shifts caused MORE disruption to the biological rhythm as it takes longer for us to adjust.

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Evidence for shift work

Moore-ede - He found an estimated cost of $77 billion were spent due to major accidents or work related illnesses, as a result of shift work.

AO2 Comment: This suggests that a conseqence of disruption biological rhythms is that it can lead to alot of money being wasted and illnesses developing.

Industrial accidents - Bhopal, Chernobyl and Three-mile Island major industrial accidents all occurred between the hours of 1am and 4am.

AO2 Comment: This suggests that shift work can disrupt our biological rhythm which can lead to less concentration and industrial accidents.

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Consequences of shift work

A positive consequence:

P- More job oppurtunities

E - Many businesses are now operating 24/7, meaning that there are more employment oppurtunities in society. This will increase the employment levelsof the country and lead to a better economy. Some of these jobs include doctors and nurses, which means that hospitals can be open 24/7 as a result of shift work.

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C - Without hospitals open there would be alot more accidents that are occur that are NOt a result of shift work, this suggests that disrupting biological rhythms has positive conseqences.

A negative conseqence is obviously that lots of money has been spent on industrial accidents.

Another negative consequence is that sleep is very important. This is shown from research into sleep deprivation showing that REM sleep is very important and REM rebound occurs if we need to catch up. This suggests that by disrupting the biological rhythms those working shifts will be suffering from sleep deprivation while their rhythm is disrupted.

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Dealing with consewuences of shift work

Although there a negative consequence of shift work, there are ways of improving the effects:

- Use rapidly changing shifts

- Reseting the biological clock e.g. using brights lights (to reset the SCN) , it acts as a replacement for natural light, making the body think it is day time.

From people studying the effects of shift work ways of minimising the disruption have now been developed. This is a positive consequence of disrupting biological rhythms as shift work can now be conducted with a lower level of risk.

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Jet lag

The day is lengthen if we fly West, this is known as phase delay.

The day is shortened if we fly East, this is known as phase advance.

Phase advance has more negative effects than phase advance!

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Evidence for Jet Lag


  • He studied baseball teams from the U.S.A
  • Teams had crossed time zones to play away from home.
  • He found teams that has flown east were less likely to win as they suffered from phase advance.AO2 Comment: This suggests that phase advance has more negative effects, and that a negative consequence of jet lag is that it can disrupt our rhythm and have an influence of things like a basketball score.

Evaluation of this study:

+ natural study - high ecological validity

- culture bias - only used U.S.A (use evaluation from issues in unit 5)

- gender bias - only used men (use evaluation from issues in unit 5)

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Consequences of Jet Lag

A positive consequence:

P - Allows us to travel the world

E - If we did not cross time zones and put ourselves through phase advance/delay we would not be able to travel the world and visit new places, travalling by air has allowed us to do this.

C - This suggests a positive consequence of disrupting biological rhythms is that it has allowed us to travel through time zones and see different parts of the world.

P - Allows us to trade with the world

E - Without flight we would not be able to gain as much food supply as a lot of our conutries food is imported by flight. If we were not prepared to disrupt our biological rhythm we would have a low level of food and find it difficult to survive.

C - This suggests that a positive consequence of disrupting of biological rhythms is that it can help survival and keep a strong supply of food.

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Dealing with consequences of jet lag

Melatonin - cannot only resolve sleeping problems but can help the body clock adjust to a new time zone.

Adopt local eating and bed times - as soon as possible the social cues will reset the biological clock.

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There are both negative and positive consequences to disruption.

However there are ways to reduce the negative effects e.g. melatonin pills, rapid changing shifts.

Disrupting our rhythms is vital for survival and more damage would be done if we didn't.

We would have no hosptials open at night and very little food.

This suggests that although there are negative conseqences they will always be overruled by the vitality of shft work and travelling through time zones.

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