BIO: Circadian Rhythms

Question 1

define biological rhythms:

Answer 1

are recurring patterns of behavior in the body’s systems (eg. endocrine system, immune system)

Question 2

define circadian rhythms:

Answer 2

a Latin term meaning a pattern or cycle that lasts around (circa) a day (dies)

Question 3

Circadian rhythms: human evolution

Answer 3

in humans, evolutionary pressure on these rhythms included avoiding predators
- like many organisms, our biological clock responds to sunlight

Question 4

Human circadian rhythms: examples…

Answer 4

• core body temp
• sleep/wake cycle
• hormone production

Question 5

A03 support: Hughs (1977)

Answer 5

support for role of light:
people living through long, dark Antarctic winters showed changed cortisol cycles- other replications found nothing

Question 6

“Wake up lights”

Answer 6

• these simulate natural light patterns in order to make you sleepy/ alert
• they are widely used with ASD and have strong clinical support

Question 7

Chronotherapeutics (time-release drugs)

Answer 7

• some drugs take a long time to start working, and/or are most effective when taken at awkward times
• special drug coatings dissolve slowly so we can accurately time the release of a drug you took hours ago (Evans and Marain, 1996)

Question 8

Shift Work:

Answer 8

Many harmful effects of regular sleep disruption have been found in shift workers, eg.
- reduced concentration (esp in mornings)
- increased risk of depression
- heart attacks
- stroke
- (any other conditions linked to excess oxidative stress)

Question 9

Evaluation 1 (individual differences)

Answer 9

P- an issue with this research on circadian rhythms is that it ignores individual differences, meaning it does not generalise
E- studies have established a natural range of human sleep cycles between 13 and 65 hours (Czeisler et al. 1999)
E- Duffy et al. (2001) found “larks” and “owls” in human samples; the former waking early and the latter staying awake late, regardless of light or social cues.
L- These examples show the research presented here is overly determinist; mistakenly assuming small samples allow valid generalisation. The view that identical biological structures would mean identical biological rhythms reveals biological reductionism. External factors such as diet, exercise and culture are likely to account for individual differences.