Circadian Rhythms

Question 1

What is a Biological Rhythm/ a circadian rhythm?

Answer 1

• Exert an influence on how the body behaves and are governed by two thing:
• Endogenous Pacemakers - internal biological ‘clock’
• Exogenous Zeitgebers - External changes in the environment
• Circadian rhythms last 24 hours e.g body temperature

Question 2

The Sleep/Wake cycle as a Circadian Rhythm?

Answer 2

• Light acts an exogenous zeitgeber
• The suprachiasmatic nucleus acts as an endogenous pacemaker and lies just above the optic chiasm in order to provide the pineal gland with light information

Question 3

What was Siffre’s Research?

Answer 3

• No natural light (had artificial light) 6 months in a Texan cave - ‘free-running biological clock’ was around 25 hours continued to fall asleep and wake up on a regular schedule

Question 4

What other research was done on the sleep wake cycle and who was it done by?

Answer 4

• Aschoff and Wever: pps spent a month in a ww2 bunker - all but one (who extended to 29 hours) circadian rhythm was between 24 and 25 hours. Suggests natural rhythm may be just over 24 hours but is entrained by exogenous zeitgebers
• Folkard studied zeitgebers: 12 pps stayed in dark cave for 3 weeks, going to bed when clock read 11:45 and rising when it said 7:45. The clock was gradually sped up, without the participants knowing until the supposed length of a day was 22 hours. Only one pps was able to adjust well. Supports existence of a strong free-running endogenous pacemaker

Question 5

What is one limitation of research regarding generalisability?

Answer 5

• Not generalisable as individual difference e.g Duffy (2001) pointed out some people are larks and some are owls
• chronotype (whether you are a lark or an owl)

Question 6

What is one strength of research into circadian rhythms in the real world?

Answer 6

• Can be used to improve impact of medications, circadian rhythms co-ordinate processes such as heartrate, digestion, hormone levels etc which rise and fall during the day. Chronotherapeutics (medical treatment given at a time complimentary to the persons biological rhythm) e.g aspirin for a heart attack is most effective given at night

Question 7

What is another limitation of research (artificial)?

Answer 7

• Siffre’s research was potentially artificial as he used a lamp - a potentially artificial exogenous zeitgeber, meaning said light may have been keeping his circadian rhythm entrained, undermining his conclusion that we have a strong endogenous pacemaker.