Biological rhythms: circadian

Question 1

What are circadian rhythms and a example?

Answer 1

• Biological rhythms with a cycle of once in a 24 hour period
• regulate a number of processes such as the sleep-wake cycle

Question 2

What is the exogeneous zeitgeber that influences sleep-wake cycle?

Answer 2

light

Question 3

What is our endogenous pacemaker that governs the sleep-wake cycle and its role?

Answer 3

• internal ‘body clock= suprachiasmatic nucleus
• SCN lies above the optic chiasm which provides information from the eye about light

Question 4

Outline Siffre’s cave study and findings

Answer 4

• spent two months in cave to study effect of his own biological rhythm
• deprived of exposure to natural light & sound
• In each case his ‘free-running’ biological rhythm settled down to around 25 hrs
• fall and woke on regular schedule

Question 5

Outline Aschoff and Wever’s research

Answer 5

• convinced pp’s to spend four weeks in a WW2 bunker deprived of natural light

Question 6

What did Aschoff and Wever find & conclusions?

Answer 6

• all but one pp (29hrs) displayed a circadian rhythm between 24 & 25 hrs
• suggest natural sleep-wake cycle longer than 24hr but entrained by EZ’s associated with 24hr day (mealtimes, daylight etc.)

Question 7

Outline Folkard’s study

Answer 7

• studied group of 12 people who agreed to live in dark cave for 3 weeks
• went to bed when clock said 11:45 and rose when it was 7:45
• researchers gradually sped up clock (pp’s not aware)
• so an apparent 24hr day eventually only lasted 22hrs

Question 8

What did Folkard find & conclusions?

Answer 8

• only one pp was able to adjust to new regime
• suggest existence of strong free-running circadian rhythm cannot be overridden by EZ’s

Question 9

What is a strength of research into circadian rhythms?

Answer 9

• real world application
• helps us to understand consequences that occur when our circadian rhythms are disrupted
• night workers have reduced concentration at 6am (circadian trough) =mistakes/accidents more likely
• research has found that shift workers 3x likely to develop heart disease than typical work patterns
• real world app in terms of how to mange productivity

Question 10

What is a counterpoint for real world application of sleep/wake cycle research?

Answer 10

• investigating effects of shift work= correlational methods
• difficult to establish cause (disrupted s/w cycle) & effect (negative)
• may not be biological factors
• Solomon> higher divorces rates in shift workers= missing out on family events as well as deprived sleep

Question 11

What is another strength of research into circadian rhythms?

Answer 11

• used to improve medical treatments
• medical treatments can be administered in a way that it corresponds to a persons biological rhythms
• e.g. aspirin as a treatment for heart attacks is most effective at night as heart attacks usually occur in the morning, so timing of taking it matters
• research can help increase effectiveness of drug treatments

Question 12

What is a limitation of research into circadian rhythms?

Answer 12

• generalisations are difficult to make
• studies are based on small samples (low pop validity)
• Czeisler» found individual differences in s/w cycles varying from 13-65hrs
• Duffy et al» some people have natural preference for going to bed early & rise early (larks) some are the opposite (owls)
• individual difference make it difficult to generalise findings from research