Biological rhythms: circadian rhythms

Question 1

Biological rhythms: circadian rhythms

parts

Answer 1

Biological rhythms 	
The sleep/wake cycle Siffre’s cave study 	
Other research
└Aschoff and Wever (1976)
└Folkard et al (1985)

Question 2

Biological rhythms

Answer 2

distinct patterns of changes in body activity that conform to cyclical time periods
└influenced by internal body clocks (endogenous pacemakers) and external changes to the environment (exogenous zeitebers)

Question 3

circadian rhythm

Answer 3

a type of biological rhythm- 24 hour cycle
└circa= about, diem= day
└regulated body processes
└e.g. sleep/wake cycle, changes in core body temperature

Question 4

Biological rhythms

list

Answer 4

└ultradian rhythms: many times during a day
└circadian rhythm: takes a day to complete
└infradian rhythms: longer than a day to complete
└circannual rhythms: much longer to complete

Question 5

ultradian rhythms

Answer 5

many times during a day

Question 6

infradian rhythms

Answer 6

longer than a day to complete

Question 7

circannual rhythms

Answer 7

much longer to complete

Question 8

The sleep/wake cycle

Answer 8

└light is an important exogenous zeitgeber on sleep/wake cycle
└alter in day, drowsy at night

└’free running’= biological clock without the influence of external stimuli such as light

Question 9

Siffre’s cave study

Answer 9

Michel Siffre
└spent several extended periods underground to study effects of his own biological rhythms
└no access to natural light or sound, only food and drink
└caves in the Alps
└came out September 1962 after 6 months
└thought it was August
└repeated experiment a decade later
└six months in a Texan cave
└found his ‘free running’ biological rhythm was 25 hours (usual=24)
└slept/woke on a regular schedule

Question 10

Other research

list

Answer 10

└Aschoff and Wever (1976)

└Folkard et al (1985)

Question 11

Aschoff and Wever (1976)

Answer 11

└participants in WW2 bunker for 4 weeks, no natural light
└all but 1 participant (who has 29 hours)
└=circadian rhythm of 24-25 hours
└findings
└natural sleep wake cycle slightly longer than 24 hours
└exogenous zeitgebers makes it 24 hours (e.g. hours of daylight)

Question 12

Folkard et al (1985)

Answer 12

└12 people, dark cave, 3 weeks
└wake up when clock said 7.45 am
└go to bed when clock said 11.45 pm
└secretly sped up the clock over study
└24 hour day → 22 hour day
└findings: only one participant adjusted well to new regime
└suggests circadian rhythm cant easily be overridden by changes in external environment

Question 13

Biological rhythms: circadian rhythms
strengths
summary

Answer 13

Practical application to shift work- Boivin et al (1996), Knutsson (2003)

Practical application to drug treatments - Baraldo 2008

Question 14

Biological rhythms: circadian rhythms
strengths
Practical application to shift work

Answer 14

└knowledge of circadian rhythms
└better understanding of negative consequences that can occur because of their disruption (desynchronisation)
└e.g. Boivin et al (1996)
└night workers that do shift work experienced a period of reduced concentration around 6 in the morning (a circadian trough)
└=mistakes are more likely
└Knutsson (2003)
└link between shift work and poor health
└shift workers 3 times more likely to develop heart disease
└may be due to stress of adjusting to different sleep/wake patterns
└research into sleep/wake cycle may have economic implications
└how best to manage worker productivity

Question 15

Biological rhythms: circadian rhythms
strengths
Practical application to drug treatments

Answer 15

└circadian rhythms coordinate some of the body’s basic processes
└e.g. heart rate, digestion, hormone levels
└=has an effect on pharmacokinetics
└(how well drugs are absorbed and distributed in the body, how effective they are)
└research shows there are certain peak times in the day/night where drugs are likely to be most effective
└=led to development of guidelines to do with the timing of drug dosing of medications
└e.g. anticancer, cardiovascular, anti-ulcer, anti-epileptic drugs (Baraldo 2008)

Question 16

Biological rhythms: circadian rhythms
limitations
summary

Answer 16

Use of case studies and small samples - Aschoff and Wever (1976), Michel Siffre

Poor control in studies - Czeisler et al (1999)

Individual differences - Czeisler et al (1999), Jeanne Duffy et al (2001

Question 17

Biological rhythms: circadian rhythms
limitations
Use of case studies and small samples

Answer 17

└studies of the sleep/wake cycle usuallt involve small groups of participanss or single individuals
└e.g. Aschoff and Wever (1976), Michel Siffre
└may not be representative, cant generalise to wider population
└ Michel Siffre (1999)
└most recent cave experiment, age 60
└internal clock ticked slower than when he was younger
└shows even when the same person is involved, there are factors that vary which may prevent general conclusions being draw

Question 18

Biological rhythms: circadian rhythms
limitations
Poor control in studies

Answer 18

└participants in studies didn’t have natural light, still had artificial light
└e.g. Siffre turned lamp on while he was awake
└it was assumed that artificial lite has no effect on free running biological rhythm
└Charles Czeisler et al (1999)
└was able to adjust participants circadian rhythms from 22 → 28 hours using dim lighting
└confounding variable
└the use of light may be the same as taking a drug that resets their biological clock

Question 19

Biological rhythms: circadian rhythms
limitations
Individual differences

Answer 19

└Czeisler et al (1999)
└individual cycles can vary 
  └from 13-65 hours 
└Jeanne Duffy et al (2001)
  └some people display a natural preference for going to bed/rising early (larks)
  └others show the opposite (owls)
└age differences in sleep/wake cycle