Biological Rhythms: Circadian Rhythms

Question 1

what is a biological rhythm?

Answer 1

• distinct pattern of changes in body activity that conform to cyclical time periods

Question 2

what are the 3 types of biological rhythms?

Answer 2

• circadian
• ultradian
• infradian

Question 3

what is a circadian rhythm?

Answer 3

a type of biological rhythm subject to a 24hr cycle, which regulates a number of body processes
- these include sleep/wake cycle and changes in the core body temperature
- they are both affected by endogenous pacemakers and exogenous zeitgebers

Question 4

what is an endogenous pacemaker? (and an example)

Answer 4

internal body clocks
- SCN (suprachiasmaticnucleus)

Question 5

what is an exogenous zeitgeber and give an example?

Answer 5

external changes, cues, in the environment
- e.g. light

Question 6

what does research into circadian rhythms include?

Answer 6

• ‘free running’ body clock which refers to the removal of light as a time cue and observing the effects on sleeping patterns

Question 7

who are the researchers involved in the research into circadian rhythms?

Answer 7

• Siffre
• Aschoff and Weaver
• Folkard et al

Question 8

what did Siffre do?

Answer 8

• cave explorer who spent extended periods of time underground
• wanted to investigate the effect of this on his free-running circadian rhythm
• deprived of natural light and sound with access to food and drink
• kept a diary of his sleep and wake patterns
• initial sleep patterns were erratic and then settles down to a regular rhythm
• his natural circadian rhythm without exogenous zietgebers was 25 hrs
• spent two months in a cave but according to his days he had only been there for 1.5 months
• repeated a decade later and spent 6 months in a cave, recording the same results

Question 9

what did Ashoff and Weaver do?

Answer 9

• 4 weeks in a WW2 bunker
• 26 ppts
• deprived of light
• all but one ppt displayed circadian rhythms of 24-25 hrs
• one ppts circadian rhythm extended to 29hrs

Question 10

what did Folkard et al do?

Answer 10

• 12 poeple lived in a cave for 3 weeks
• went to bed at 11:45pm and rose at 7:45am
• researchers sped up the clock so 24 hrs went to 22 hrs
• only one ppt was able to adjust

Question 11

what are the evaluations for circadian rhythms?

Answer 11

• understanding the disruption caused by shift work
• practical application to drug therapy
• use of case studies and small samples