Circadian Rhythms

Question 1

What is a biological rhythm?

Answer 1

-Cyclical change in the way bio systems behave, repeated periodically and controlled by endogenous pacemakers and/or exogenous zeitgebers

Question 2

What is a circadian rhythm?

Answer 2

A rhythm lasting approximately 24 hours

Question 3

What is the sleep/wake cycle

Answer 3

The 24 hour cycle in which we fall asleep and wake up, widely believed to be heavily influenced by external cues such as sunlight/social interaction. However, also internal clock which is free running

Question 4

What did Michael Siffre do?

Answer 4

• Underground stays on 3 occasions

- Absence of exogenous zeitgebers such as daylight, clocks, radio

Question 5

What was the only thing influencing Siffres behaviour?

Answer 5

The ‘free running’ internal clock

Question 6

Siffre’s First Stay…

Answer 6

Alps, 61 days, resurfaced believing it was 20th of August when it was the 17th of September

Question 7

Siffres Second Stay…

Answer 7

Texan cave for 6 months, rhythm settled to just over 24 hours but could shift to as many as 48

Question 8

Siffres Third Stay…

Answer 8

To observe the effects of ageing. Found internal clock ticked more slowly compared to when he was younger

Question 9

What does Siffres research highlight?

Answer 9

The existence of an internal circadian clock that is able to work independently. Importance of exogenous zeitgebers in regulating it tho

Question 10

Siffre’s findings were supported by Aschoff and Wever…

Answer 10

• WW2 bunkers without any external cues

- Rhythms were found to be 24/25 hours, some as high as 29

Question 11

What do Aschoff and Wevers WW2 bunker studies show?

Answer 11

Gives further credit to the idea there is an internal bio clock that can persist without the influences of external cues

Question 12

However, a criticism of research into circadian rhythms is that there is a critical flaw in terms of research methodology..

Answer 12

• Still exposed to external cues (artificial light)

- Lacks validity as does not reflect changes that would occur in complete absence

Question 13

The importance of this methodological flaw is reinforced by Czeisler…

Answer 13

Rhythms could be manipulated and reduced to 22 ours or increased to 28 hours using dim lighting - role of external cues

Question 14

Further criticism of circadian rhythm research is that it ignores the role of individual differences…

Answer 14

• Cycles can range from 13 hours to 65 hours
• Morning people prefer to rise early and vice versa
• Siffre had concluded sleep wake cycle was 24 hours?

Question 15

External validity of Siffres research has been questioned…

Answer 15

• Treated as case study rather than experiment

- Lacks generalisability, how Siffre’s clock reacted does not reflect others

Question 16

Research into circadian rhythms are typical of the biological approach, thus determinist…

Answer 16

• Study of blind man supportive of bio approach

- His internally set rhythm could not be changed, despite exogenous zeitgebers used to try and influence it

Question 17

What does the study of a young blind man suggest?

Answer 17

• S/W cycles/C rhythms are biologically ingrained and can work in the absence of external cues

Question 18

HOWEVER, the human body is far more complex than this deterministic, and therefore reductionist view…

Answer 18

• Human body is far more complex

- Further studies demonstrate that EX cues do play a strong role, to some degree

Question 19

Core body temperature is a second example of a circadian rhythm within our bodies. Research has shown what?

Answer 19

Lowest at 4.30am - 36 degrees
Highest at 6pm - 38 degrees
Slight trough after lunch which occurs even in the absence of food

Question 20

What is a positive application of research into core body temperatures?

Answer 20

Knowledge can be used to heighten our cognitive abilities

Question 21

What was Folkard’s research? (RWA)

Answer 21

• Learning abilities of 12/13 y/os
• Stories read either at 9am or 3pm
• After one week the afternoon group were superior in both research and comprehension (8% more)

Question 22

What can Folkard’s knowledge be used for?

Answer 22

Can be of great use to people when performing cognitive tasks as they help people become aware of when their potential is at its highest

Question 23

What is another positive application aside from cognitive abilities?

Answer 23

• Chronotheraputics (how timing affects drug effectiveness)
• Circadian rhythms affect heart rate, hormones, digestion etc
• Drugs targeted at specific hormones can be taken when hormone level is high to work at their optimum

Question 24

So what has knowledge of circadian rhythms allowed us to do (chronotheraputics)

Answer 24

Increase the effectiveness of medication and ultimately health