biological rhythms Flashcards
(26 cards)
what are biological rhythms
patterns of changes in body activity that conform to cyclical time periods
types of biological rhythms
- circadian
- ultradian
- infradian
circadian rhythms
last around 24 hours
examples of circadian rhyhms
- sleep/wake cycle
- core body temperature
the sleep/wake cycle as a circadian rhythm
we are alert during the day and drowsy at night
- this is because of light
- but, what if there were no external stimuli?
Siffre study application
provides evidence for the idea that the sleep/wake cycle is circadian even when there is no presence of light
Siffre method
spent around 2 months in a cave
- deprived of natural light
- his ‘free-running’ biological rhythm was around 25 hours (pretty similar to normal)
Siffre cons
- poor control
- had a lamp (artificial light) turned on all day whilst he was awake
- assumed artificial light had no effect
- disproved, researcher managed to adjust ppts circadian from 22 to 28 using dim light so artificial light is comparable to natural
Aschoff and Wever
convinced ppts to stay in a WW2 bunker for 4 weeks deprived of natural light
- all ppts displayed a circadian rhythm of 24-25 hours
- except 1, who has 29 hours
Folkard et al
group of 12 lived in a cave for 3 weeks
- told them to gts at 11:45 and wake at 7:45
- but it wasn’t actually 11:45, he sped up the clock slightly everyday
- eventually 24 hours became 22 and only 1 ppt comfortably adjusted to this
- suggests circadian rhythm cannot easily be overridden
support for circadian rhythms
practical application - Boivin et al
Boivin et al
E - night workers engaged in shift work w less concentration at 6am
E - mistakes and accidents are more likely when circadian is disrupted
L - knowledge of circadian has given understanding of consequences when disrupted
what is circadian trough
when activity and alertness are at their lowest
what is desynchronisation
when the circadian rhythm is disrupted
infradian rhythms
biological rhythm w frequency of less than 1 cycle in 24 hours
- lasts longer than 24 hours and happens less than once in that time
examples of infradian rhythms
- menstrual cycle
- seasonal affective disorder (SAD)
McClintock
endogenous systems can be influenced by exogenous factors
- 29 women w irregular periods
- collected pheromones from 9, cotton pad placed in armpit and kept for a day
- rubbed these pads in other ppts upper lip
- found 68% experienced changes to cycle bringing them closer to ‘odour donor’ cycle
SAD
depressive disorder
-particular type of infradian known as ‘circannual rhythm’ bc its a yearly cycle
- also thought to be circadian bc could be due to disruption of sleep/wake cycle
The role of melatonin in SAD
At night the pineal gland releases melatonin until dawn when there is light
- during winter the lack of light means the secretion process continues for longer
- this interferes with the production of Serotonin which has been linked to the onset of depressive symptoms
ultradian rhythms
A biological rhythm with a frequency of more than one cycle in 24 hours
the sleep/wake cycle
example of an ultradian rhythm
- psychologist have identified five distinct stages of sleep that altogether span around 90 minutes
Stage 1and 2
known as the ‘sleep escalator’
- stage of light sleep where the person may easily be woken
- Brain wave patterns start to become slower and more rhythmic (alpha waves) which becomes slower as the sleep becomes deeper (theta waves)
Stage 3 and 4
involve delta waves which are slower and greater amplitude than alpha and theta
- a deep sleep/ slow wave sleep and is difficult to wake someone at this point
Stage 5 (REM)
The body is paralysed yet the brain activity speeds up significantly in a manner that resembles an awake brain
- Highly correlated with the experience of dreaming
