biological rhythms: ultradian rhythms Flashcards
1
Q
what are ultradian rhythms?
A
a type of biological rhythm with a frequency of more than one cycle in 24 hours
2
Q
describe the cycle of sleep
A
- 5 distinct stages
- spans approximately 90 minutes
- continues throughout the course of the night
- each stage is characterised by a different level of brain wave which can be monitored using an EEG
3
Q
describe stages 1 of sleep
A
- light sleep where a person may easily be woken
- brain waves are high frequency and have short amplitude
- alpha waves
4
Q
describe stage 2 of sleep
A
- alpha waves contiue
- occasional random changes in pattern called sleep spindles
5
Q
describe stages 3 and 4 of sleep
A
- known as deep sleep or slow wave sleep (SWS)
- brain waves are delta waves with lower frequency and higher amplitude
- difficult to wake someone at this point
6
Q
describe stage 5 of sleep
A
- REM sleep
- body is paralysed yet brain activity closely resembles that of the awake brain
- brain produces theta waves
- eyes occasionally move around, thus rapid eye movement
- dreams are most often experienced during REM sleep but may also occur in deep sleep
7
Q
EEGs and sleep
A
- EEGs are used to measure brainwaves in controlled laboratories
- this enables researchers to describe the changes in neural activity during sleep
- digitalised computer images of brainwaves have replaced paper printouts in the last few years as the technology has become more sophisticated
- participants are usually required to arrive at the lab having missed a night’s sleep so they are able to go to sleep relatively quickly
8
Q
what is the basic rest-activity cycle? (BRAC)
A
- kleitman (1969) suggested a similar 90-minute rhythm cycle that continues during the day
- characterised by a period of alertness followed by a spell of physiological fatigue
- this recurs during the course of the day
9
Q
evidence for BRAC
A
- anecdotal evidence supports the existence of BRAC such as the frequent observation that students find it difficult to concentrate for periods longer than 90 minutes at a time
- in a widely-cited study of prodigious violinists, ericsson et al. (1993) found the best performers tended to practice for 3 sessions during the course of the day, each session lasting no more than 90 minutes and there being a break between each to ‘recharge’
10
Q
evaluation: improved understanding of age-related changes in sleep
A
- sleep scientists have observed that SWS reduces with age
- growth hormone is mostly produced during SWS so this is reduced in older people
- cauter et al. (2000) suggested that the resulting sleep deficit may explain various issues in old age, such as reduced alterness
- to increase SWS, relaxation and medication may be used
- this suggests that knowledge of ultradian rhythms has practical value
11
Q
evaluation: significant variation between people
A
- tucker et al. (2007) found large differences between participants in terms of the duration of each sleep stage, particularly stages 3 and 4
- tucker et al. suggests that these differences are likely to be biologically determined
- this makes it difficult to describe ‘normal sleep’ in any meaningful way
12
Q
evaluation: the sleep lab
A
- benefits of conducting studies of sleep in lab settings is that extraneous variables can be controlled
- researcher can exclude temporary variables such as noise or temperature that may affect sleep
- however, lab studies involve being attached to complicated machinery, leading participants to sleep in a way that does not represent their ordinary sleep patterns
