Biological rhythms: Circadian rhythms

Question 1

What is a biological rhythm?

Answer 1

Distinct patterns of changes in body activity that conform to cyclical time periods.

Question 2

What is a circadian rhythm?

Answer 2

A biological rhythm which lasts around 24 hours

Question 3

What was Siffre’s cave study and what did it show?

Answer 3

• Siffre spent several extended periods underground with no way to record time.
• In the first study, he emerged in September believing it to be mid-august (as a result of his sleep/wake cycle having extended to around 25 hours)
• When he repeated the study for 6 months in a Texan cave 10 years later, he adapted to the same/similar sleep/wake cycle

Question 4

What was Aschoff and wever’s study and what did it show?

Answer 4

• A group of participants spent 4 weeks in a WWII bunker
• All adapted to a 24-25 sleep wake cycle except one who’s cycle extended to 29 hours
• This supports the idea put forward by Siffre’s study that the natural sleep/wake cycle may be slightly longer than 24 hours

Question 5

What was Fokard et al’s study and what did it show?

Answer 5

• 12 people agreed to live in a dark cave for 3 weeks, sleeping from 11.45pm to 7.45am
• Gradually the “24 hour day” was sped up to only last 22 hours
• Only one participant adapted confortably

Question 6

What practical applications does this research have? (shift work)

Answer 6

• Knuttson (2003) found a correlation between shift workers and the chances of having a heart attack (on average 3 times more likely than everyone else).
• Suggests that deviating or disrupting circadian rhythms too drastically can have serious health connotations
• Thus research can be used to help make workers more productive-more efficient/reliable work scheduling

Question 7

What other practical applications does this research have? (drug treatment)

Answer 7

• It has been found that circadian rhythms have an effect on pharmokinetics
• Because of this, it can be determined when is the best time to take medicine (first thing in the morning/before food/last thing at night)

Question 8

How can these studies relating to circadian rhythms be criticised?

Answer 8

• They all either used small groups are were case studies
• Poor control-access to artificial light
• Poor control-uncontrolled food consumption

Question 9

What did Czeisler et al find that may undermine the results of these studies?

Answer 9

Due to individual differences- a person’s ‘natural’ sleep/wake cycle can vary between 13 and 65 hours, meaning there may be no truly universal traits relating to circadian rhythms