Biological rhythms: Circadian rhythms

Question 1

What are biological rhythms?

Answer 1

A change in body processes or behaviour in response to cyclic changes in the environment

Question 2

What are the 2 things biological rhythms are controlled by?

Answer 2

• body’s internal biological ‘clock’ (endogenous pacemakers)
• external changes in the environment ( exogenous zeitgebers)

Question 3

What are circadian rhythms?

Answer 3

A type of biological rhythm that lasts for around 24 hours

Question 4

What are 2 examples of circadian rhythms?

Answer 4

sleep/wake cycle & core body temperature

Question 5

What is an important exogenous zeitgeber on our sleep/wake cycle?

Answer 5

daylight - we feel tired during the night and alert during the day

Question 6

Evaluation: Practical application to shift work

Answer 6

• knowledge about circadian rhythms has given researchers a better understanding of the consequences occurring due to disruption
• e.g night workers engaged in shift work experience reduced concentration at around 6 in the morning - mistakes more likely
• research suggests that shift workers are x3 more likely to develop heart disease which partly may be due to the stress of adjusting to different sleep/wake cycles
• research into sleep/wake cycle may have economic implications in terms of how to best manage work productivity

Question 7

Evaluation: Practical application to drug treatments

Answer 7

• circadian rhythms co-ordinate many of the body’s processes like heart rate, digestion & hormone levels
• this therefore effects the action of drugs in the body & how well they’re absorbed and distributed
• research suggests that there are certain peak times during the day & night where drugs are likely to be the most effective
• this led to development of guidelines about when to time certain drugs including anticancer, cardiovascular & respiratory

Question 8

Evaluation: Use of case studies & small samples

Answer 8

• studies of sleep/wake cycles tend to consist of small groups or individuals (like Siffre’s study)
• these people may not be able to represent a wider population which limits the extent of meaningful generalisation
• Siffre observed that at the age of 60 his internal clock was much slower which shows that even if the same person is involved the results can’t be generalised

Question 9

Evaluation: Poor control in studies

Answer 9

• although pps in the studies were deprived of natural light they still had access to artificial light
• e.g Siffre turned on a lamp every time he woke up which stayed on until he went to bed again
• it was only assumed that artificial light would not effect his biological rhythm
• Charles Czeisler was able to adjust pps’ circadian rhythms using dim lighting which proves that the use of light can correspond to biological clocks