Circadian Rhythms

Question 1

Research support for the importance of light:

Hughes (1977)

Answer 1

tested the circadian hormone release in 4 participants.

At the end of the antarctic summer, cortisol levels reaching their highest point as participants woke and lowest when they went to bed

But after 3 months of continuous darkness, this changed to peak levels at noon rather than when they woke

this shows how extreme daylight doing in polar regions of the world may be responsible for variations in circadian hormone release

Question 2

Individual differences:

Answer 2

one major individual difference is the CYCLE LENGTH - varying from 13 to 65 hours

the other difference relates to CYCLE ONSET - individuals appear to be innately different in terms of when their circadian rhymes reach their peak

D: e.g. he found that ‘morning people’ prefer to rise early and go bed early and ‘evening people’ wake and go bed later

Question 3

Research methodology:

Cziesler (1999)

Answer 3

research sufferers a flaw when estimating the ‘free-running’ cycle of the human circadian rhythm

in most studies, participants are isolated from variable that might affect their circadian rhythms i.e. clocks, daylight. However they aren’t isolated from artificial light as it’s believed that it won’t affect their CR

However, Cziesler altered participants circadian rhythms down to 22hrs and up to 28hrs using artificial lighting alone

Question 4

Chronotherapeutics:

Answer 4

a real world application of CR is chronotherapuetics, studying how timing affects drug treatments

the specific time patients take their medication and the concentration of the drug is important to its success

e.g. risk of heart attack is greatest in the morning thus drugs have been developed that have novel delivery systems i.e. taking the drug at night but it doesn’t take action till the morning