Circadian Rhythms

Question 1

how long do circadian rhythms last?

Answer 1

around 24 hours

Question 2

what are examples of circadian rhythms?

Answer 2

sleep/wake cycle

body temperature

Question 3

how do exogenous zeitgebers affect the sleep/wake cycle?

Answer 3

daylight affects how we feel drowsy at night and alert during the day

Question 4

how do endogenous pacemakers affect the sleep/wake cycle?

Answer 4

the suprachiasmatic nucleus recieves information about light

light can reset the SCN

Question 5

what did Siffre do in 1962 and 1970?

Answer 5

he was deprived of natural light and sound in the caves of the Southern Alps, but had access to adequate food and drink

he resurfaced in mid-september after 2 months, believing it to be mid-august

1970- performed a similar feat for 6 months in a Texan cave

Question 6

what did Siffre’s cave study find?

Answer 6

his ‘free-running’ biological rhythm settled to just above 24 hours (about 25 hours) though he did continue to fall asleep and wake up on a regular schedule

Question 7

what did Ashoff and Wever (1976) do?

Answer 7

convinced a group of participants to spend 4 weeks in a WW2 bunker deprived of natural light

Question 8

what did Ashoff and Wever (1976)’s study’s results?

Answer 8

all but one (whose sleep/wake cycle extended to 29 hours) displayed a circadian rhythm between 24-25 hours

Question 9

what did Siffre and Ashoff and Wever’s study suggest,

Answer 9

the natural sleep/wake cycle may be slightly longer than 24 hours, but is entrained by exogenous zeitgebers associated with our 24 hour day

Question 10

what did Simon Folkard (1985) study?

Answer 10

a group of 12 people who lived in a dark cave for 3 weeks, going to bed when the clock said 11:45pm, and waking when it said 7:45am

the researcher gradually sped up the clock (not known by the participants) so an apparent 24 hour day only lasted 22 hours

Question 11

what was Simon Folkard (1985)’s study’s results?

Answer 11

only one participant comfortably adjusted to the new regime

suggests the existence of a strong free-running circadian rhythm cannot be easily overridden by changes in the environment

Question 12

how does body temperature vary throughout the day?

Answer 12

varies around 2°C

lowest at around 4am (36°C), and peaks at around 6pm (38°C)

Question 13

what did Folkard (1977) find out about core body temperature?

Answer 13

children who had stories read to them at 3pm showed better recall and comprehension after a week compared to children who heard the same story at 9am

Question 14

what did Gupta (1991) find out about core body temperature?

Answer 14

found improved performance on IQ rests when participants were assessed at 7pm opposed to 2pm and 9am

Question 15

how do teenage circadian rhythms differ from adults’?

Answer 15

typically begin 2 hours after adults’

so current school start times mean their body still needs to wake up too early and are trying to focus when they still need sleep, and at night they are not as tired as they’re supposed to be

Question 16

what was the study about teenage circadian rhythms?

Answer 16

pilot study at Monkseaton High School in North Tyneside put the start stone to 10am

found academic results went up, illness down and atmosphere in school was ‘bliss’

Question 17

what are the strengths of research into circadian rhythms?

Answer 17

practical application to shift work - Boivin et al (1996) - shift workers experience a lapse of concentration around 6am so accidents more likely

practical application to drug treatment - Baraldo (2008) - there are times in the day when drugs are likely to be at their most effective

Question 18

what are the limitations of research into circadian rhythms?

Answer 18

small samples in studies

poor control in studies - still had access to artificial light

individual differences - Duffy et al (2001) - some people display a natural preference for sleeping and rising early (‘larks’) but ‘owls’ prefer the opposite