Circadian Rythms

Question 1

What is a circadian rhythm?

Answer 1

• last 24 hours

- e.g sleep wake cycle

Question 2

Describe our internal body clock

Answer 2

• regulated by our internal system

- e.g by hormones, metabolic rate and body temp

Question 3

What are the 2 key researchers for circadian rhythms?

Answer 3

• Siffre (1975)

- Aschoff and Weber (1962)

Question 4

Describe Siffre’s research

Answer 4

• spent 6 months in cave
• measures sleep wake cycle without any idea of time
• Day lengthened to 25 hours
• he was in there for 179 days
• he thought it was 151 days

Question 5

Describe Aschoff and Weber’s research

Answer 5

• spent 4 weeks in WW2 bunker
• deprived of natural light
• had control over electrical lights
• most body clocks ended up as 24-25 hours
• one was extended to 29

Question 6

What are the conclusions of Siffre and Aschoff and Weber’s research?

Answer 6

• both prove endogenous pacemakers exist
• p’s kept circadian rhythms without external cues
• exogenous zeitgebers are needed to maintain a normal sleep wake cycle

Question 7

What are the 2 variations of the sleep wake cycle?

Answer 7

• night owls / larks

- age

Question 8

How are night owls / larks a variation of sleep wake cycle?

Answer 8

• some wake early and become productive quickly
• they become less alert as day goes on
• night owls reach peak performance in the afternoon / late evening

Question 9

How is she a variation of the sleep wake cycle?

Answer 9

• young Sleep early and wake early
• as young age their circadian rhythm’s change
• they prefer to go bed later and get up later
• then as they become adults they prefer sleeping earlier age waking up earlier

Question 10

What are the strengths of circadian rhythms?

Answer 10

• supporting research

- practical applications

Question 11

What is the supporting research for circadian rhythms?

Answer 11

• Folkard (1985)
• 12 p’s lived in dark cave for 3 weeks
• slept at 11:45 pm and wake at 7:45 am (according to clock)
• researchers sped up clock
• 24 hours reduced to 22
• p’s couldn’t adjust
• supports internal body clock can’t be overridden by external cues

Question 12

What are the practical applications of circadian rhythms?

Answer 12

• shift work needs p’s to adjust sleep work cycle
• negative consequences for health
• 3x more likely to get heart disease
• maybe due to stress of adjusting and lack of good quality sleep
• can use to better health and NHS

Question 13

What are the limitations of circadian rhythms?

Answer 13

• individual differences
• methodology
• methodology 2

Question 14

How are individual differences a weakness of circadian rhythms?

Answer 14

• cycle length can vary from 13 - 65 hours
• Duffy (2001) :
• morning people have a usual day 6-10
• evening people have a usual day 10 - 1

Question 15

How is methodology a weakness of circadian rhythms? (Control)

Answer 15

• poor control
• in studies p’s weren’t isolated from artificial light
• they thought dim artificial light wouldn’t affect circadian rhythms
• Czeisler (1999)
• rhythms can adjust from 22 to 28 hours with artificial light

Question 16

How is methodology a weakness of circadian rhythms? (Sample)

Answer 16

• Small sample size
• Siffre - 1, folkard - 12
• Siffre re did study when 60
• internal clock was much slower than when younger
• can’t generalise