Biological Rhythms: circadian rhythms

Question 1

circadian rhythms definition

Answer 1

biological rhythms, subject to a 24 hour cycle, which regulates a number of body processes such as sleep/wake cycle and changes in core body temperature

Question 2

biological rhythms definition

Answer 2

distinct patterns of changes in body activity that conforms to cyclical time periods. biological rhythms are influenced by internal body clocks (endogenous pacemakers) as well as external changes to the environment (exogenous zeitgebers)

Question 3

who is subject to biological rhythms

Answer 3

all living organisms such as pants, animals and people

Question 4

what do biological rhythms exert

Answer 4

an important influence on the way in which body systems behave

Question 5

what are all biological rhythms determined by

Answer 5

-endogenous pacemakers
-exogenous zeitgebers

Question 6

what are endogenous pacemakers

Answer 6

the body’s internal biological clocks

Question 7

what are exogenous zeitgebers

Answer 7

external changes in the environment

Question 8

are endogenous pacemakers internal or external

Answer 8

internal

Question 9

are exogenous zeitgebers internal or external

Answer 9

external

Question 10

what rhythms occur during the day

Answer 10

ultradian rhythms

Question 11

what rhythms take longer than a day to complete

Answer 11

infradian rhythms

Question 12

what rhythms take much longer than a day to complete

Answer 12

circannual rhythms

Question 13

how long do circadian rhythms last

Answer 13

about 24 hours

Question 14

2 examples of circannual rhythms

Answer 14

-sleep/wake cycle
-core body temperature

Question 15

what does feeling drowsy at night and alert in the day demonstrate

Answer 15

the effect of daylight which is an exogenous zeitgeber on our sleep/wake cycle

Question 16

what is the sleep wake cycle also governed by in addition to exogenous zeitgebers

Answer 16

an internal endogenous pacemaker (biological clock) called the suprachiasmatic nucleus (SCN)

Question 17

what is the suprachiasmatic nucleus (SCN)

Answer 17

an internal endogenous pacemaker (biological clock) in the sleep/wake cycle

Question 18

where is the suprachiasmatic nucleus (SCN)

Answer 18

lies just above the optic chiasm which provides information form the eye about light. exogenous zeitgebers (light) can reset the SCN

Question 19

Siffre research

Answer 19

spent several extended periods underground in a cave to study the effects of his own biological rhythms, as had no exposure to natural light

Question 20

Siffre 1962 research

Answer 20

spent 2 months in caves in the southern alps, with no natural light. he left the caves in mid September and believed it to be mid august. his free running biological rhythm settled down to about 25 hours and continued to fall asleep and wake on a regular cycle

Question 21

Siffre 1972 study

Answer 21

stayed in a cave again but this time for 6 months and in a Texan cave, with no natural light. again, his free running biological rhythm settled down to about 25 hours and continued to fall asleep and wake on a regular cycle

Question 22

when did Aschoff and Wever do research

Answer 22

1976

Question 23

Aschoff and Wever procedure

Answer 23

group of participants stayed in world war 2 bunker for 4 weeks, with no natural light

Question 24

Aschoff and Wever findings

Answer 24

all but one participant displayed a circadian rhythm of between 24 and 25 hours. the one participants was 29 hours. both this and Siffre study suggest that the natural sleep/wake cycle may be longer than 24 hours but it is entrained by exogenous zeitgebers associated with our 24 hour day

Question 25

who did research saying we should not overestimate importance of exogenous zeitgebers on our internal biological clock

Answer 25

Folkard et al (1985)

Question 26

Folklard et al sample

Answer 26

12

Question 27

Folkard et al procedure

Answer 27

studied a group of 12 who agreed to live in a cave with no natural light for 3 weeks. they went to bed when the clock said 11:45 and woke when the clock said 7:45. however, over the study the clock was sped so what seemed like a 24 hour day was only 22 hours

Question 28

Folkard et al findings

Answer 28

-only one participant was able to comfortably adjust to the 22 hour day
-this suggests that the existence of a string free-running circadian rhythm cannot be easily overridden by exogenous zeitgebers

Question 29

limitation of Circadian rhythms- shift work

Answer 29

-research into circadian rhythms provides and understanding of the adverse consequences that occur when they are disrupted (desynchronisation)
-night workers engaged in shift work experience a period of reduced concentration at around 6 am called a circadian trough, this means mistakes and accidents are more likely to happen (Bovin et al 1996). Research also pointed to a relationship between shift work and poor health as shift workers are more than 3x likely to develop heart disease than those with a more typical work pattern (Knutsson 2003) –> shows that research into sleep/wake cycle can have a real-world economic implication in terms of how best to manage worker productivity

Question 30

limitation of circadian rhythms- counterpoint to shift work

Answer 30

-studies investigating effects of shift work tend to use correlational methods. can be difficult to establish if desynchronisation of the sleep/wake cycle can actually cause negative effects as there may be other factors. Soloman 1993 concluded that high divorce rates in shift workers may be due to strain of sleep deprives or other influences such as missing family events –> suggests may not be biological factors creating the adverse consequences associated with shift work

Question 31

strength of circadian rhythms- medical treatment

Answer 31

-used to improve medical treatments
-circadian rhythms co-ordinate a number of the bodys basic processes such as heart rate, digestion and hormone levels. these rise and fall during the day which has led to the field of chronotherapeutic (how medical treatment can be administered in a way that corresponds to a person’s biological rhythms) for example, how aspirin as a treatment for heart attacks is most effective when taken last thing at night. aspirin reduces blood platelet activity and can reduce risk of a heart attack. as heart attacks are most likely to occur in the morning, the time of taking aspirin matters. Bonten et al 2015 research has supported this –> shows that circadian rhythm research can help increase effectiveness of drug treatments

Question 32

limitation of circadian rhythms - individual differences

Answer 32

-generalisations can be difficult to make
-studies such as ASchoff and Wever, Siffre are based on very small samples of participants. it seems sleep and wake cycles vary widely form person to person. Czeisler et al 1999 found individual difference in sleep/wake cycles varying from 13 to 65 hours. in addition Duffy et al 2001 revealed that some people have natural preferences for going to bed early and rising early (larks) whilst others going to bed late and rising late (owls). Even Siffre, later in 1999 study observed his own sleep/wake cycle had slowed down since he was young –> means it is difficult to use research data to discuss anything more than averages, which may be meaningless

Question 33

evaluation of circadian rhythms - shifting the school day

Answer 33

-number of researchers such as Wolfson and Carskadon 1998 recommend that the school day start a couple of hours later to fit in with the typical teenage chronotype (sleep pattern). hormonal shifts in the teenage body mean that getting to sleep becomes more difficult and therefore adolescent students tend to be rather sleepy at the start of the school day. research has shown benefits for academic and behavioural performance when lessons start in the day, including reduced dependence on caffeine
-however, shifting the start of the day is disruptive for parents and teachers, and limits the number of extracurricular activates after school, also critics of the proposal suggest that a later school day would not actually reduce sleep deprivation, it would simply mean that teenagers stay up later and would still be exhausted