biological rhythms - circadian rhythms Flashcards
1
Q
biological rhythms
A
- exert an important influence on how body systems behave
- rhythms governed by endogenous pacemakers (internal biological clocks) and exogenous zeitgebers (external changes in the environment)
- ultradian rhythms occur many times throughout the day and infradian rhythms take longer than a day to complete, circannual rhythms take much longer
- circadian rhythms last for around 24 hours, for example the sleep/wake cycle and core body temperature
2
Q
the sleep/wake cycle
A
- we feel drowsy at nighttime and alert during the day, example of the effect of daylight (an exogenous zeitgeber) on our sleep/wake cycle
- also governed by an endogenous pacemaker, called the suprachiasmatic nucleus, lies just above the optic chiasm which provides information from the eye about light
- exogenous zeitgebers such as light can reset the SCN
3
Q
Siffre’s cave study
A
- caveman who spent extended periods underground to research effects on his biological rhythms
- he was deprived of natural light or sound but had adequate food and drink, resurfaced mid-september 1962, believed it to be mid-august
- his ‘free-running’ biological rhythm settled to one that was just beyond the 24 hours (about 25), however he did continue to fall asleep and wake up on a regular schedule
4
Q
other research - Aschoff, Wever, Folkard
A
- Aschoff and Wever had participants spend 4 weeks in a WW2 bunker deprived of natural light
- all but one displaced a circadian rhythm between 24-25 hours
- both Siffre’s study and this study suggest that the natural sleep/wake cycle may be slightly longer than 24 hours, but is entrained by exogenous zeitgebers associated with our 24 hour day, such as daylight hours
- Folkard studied 12 people who lived in a dark cave for 3 weeks, going to bed when the clock hit 11:45pm and waking when it said 7:45am
- without telling the group, researchers slowly sped up the clock overtime, and by the end of the 3 weeks the 24 hour days were actually only 22 hours
- only one of the participants comfortably adapted to this new regime, suggesting the existence of a strong free-running circadian rhythm that is not easily overridden by exogenous zeitgeber
5
Q
evaluation strength - shift work
A
- provides an understanding of adverse consequences that occur when circadian rhythms are disrupted (desynchronisation)
- night workers who engage in shift work experience a period of reduced concentration at about 6am (circadian trough), meaning mistakes and accidents are more likely to happen (Boivin et al)
- research also points to a relationship between shift work and poor health, shift workers are three times more likely to develop heart disease than those who work more typical work patterns
- research into the sleep/wake cycle has real-world economic implications in terms of how to manage worker productivity
6
Q
evaluation strength - medical research
A
- research has been used to improve medical treatments
- circadian rhythms coordinate some basic processes such as heart rate, digestion and hormone levels
- these rise and fall during the day which has led to the field of chronotherapeutics - how medical treatment can be administered in a way that corresponds to the patient’s biological rhythms
- for example, aspirin for heart attacks is most effective when taken last thing at night, as heart attacks are most likely to occur early in the morning
- improved drug efficacy
7
Q
evaluation limitation - individual differences
A
- generalisations are difficult to make
- most studies are based on very small samples, but it seems that sleep/wake cycles vary from person to person
- Charles Czeisler found individual differences in cycles, varying from 13-65 hours
- Jeanne Duffy found that some people have a preference for going to bed and rising early, whereas some prefer the opposite
- it is difficult to use research data to discuss anything more than averages, which may be meaningless
