Biological Rhythms: Circadian Rhythms

Question 1

What are all biological rhythms influenced by ?

Answer 1

1. Internal body clock SCN; called endogenous pacemakers
2. External changes in the environment; called exogenous zeitgebers

Question 2

What are rhythms that occur during the day called ?

Answer 2

Ultradian rhythms

Question 3

What are rhythms that are longer than 24 hours called ?

Answer 3

Infradian rhythms

Question 4

What are circadian rhythms (+ examples)

Answer 4

• last for 24 hours

Examples:
- sleep wake cycle
- core body temperature

Question 5

Describe the sleep / wake cycle - example of an exogenous zeitgeber

Answer 5

Light
- drowsy when its night and alert during the day

Question 6

Role of the sleep wake cycle and the SCN (suprachiasmatic nucleus)

Answer 6

• sleep-wake cycle controlled by endogenous pacemaker - a biological clock called SCN
• sits above the optic chiasm - provides info from the eye about light
• exogenous zeitgebers can reset the SCN - light

Question 7

Other research on biological rhythms

Answer 7

Wever - pts spent 4 weeks in a bunker deprived of natural light
- all but 1 pts showed circadian rhythm between 24-25 hrs
- suggest that the sleep wake cycle may be longer than 24 hrs

Folkard - studied exogenous zeitgebers impact on biological clock
- dark cave for 3 weeks, over time they sped up the clock so what felt like 24 hrs was actually 22 hrs.
- only 1 pts was able to adjust to the new cycle. Circadian rhythms cannot be overridden by exogenous zeitgebers

Question 8

Evaluation - strengths

Answer 8

Understanding of the adverse consequences that occur when they rhythms are disrupted
- nights works have reduced concentration at 6 in the morning - more mistakes
- research into sleep wake cycles helps in real word economic implications - worker productivity

COUNTERPOINT:
- difficult to establish whether desynchronisation of sleep wake cycle is actually a cause of -tive effects, may be other factors
- may not be biological factors that create the adverse consequences associated with shift work

Question 9

Strength

Answer 9

Improve medical treatments:
- medical treatments can be administered in a way corresponds to a persons biological rhythms
- e.g. aspirin, treats heart attacks but is best administered late at night;
Aspirin reduces platelet activity, reduces risk of a heart attacks
- circadian rhythms, increases the effectiveness of drug treatments

Question 10

Limitation

Answer 10

Generalisations are difficult to make:
- Siffre’s study is a small sample size of pts
- sleep wake cycles vary from person to person.
- some people have a natural preference for going to bed early and rising early ‘larks’ , others are opposite ‘owls’