Biopsychology: Circadian Rhythms Flashcards
Circadian rhythm
A pattern of behaviour that occurs or recurs approximately every 24 hours
Set and reset by environmental light levels
What does the sleep wake cycle do?
Dictate when humans should be asleep/awake
What does light act as in the S/W cycle?
Light acts as an external cue - primary input
S/W cycle
Light detected by eye
Message sent (in relation to brightness) to SCN (located hypothalamus)
SCN uses info to coordinate activity of entire circadian system
What does SCN use brightness levels for?
To coordinate activity within entire circadian system
Other than the sleep wake cycle, what determines sleeping and wakefulness?
Homeostasis
Role of homeostasis determining sleeping and wakefulness
Tells body needs sleep bc energy consumption
Homeostatic drive for sleep increases throughout day, max = late evening
When does homeostatic drive reach its max?
Late evening
Suprachiasmatic nucleus
Main internal body clock
Part of hypothalamus
Relies on external cues for precision
Constantly reset so body synchronised with outside world
How does the internal circadian clock run?
Free running - will maintain 24-25 hour cycle even in absence of external cues
What is the circadian system intolerant to?
Major alterations in sleep/wake cycle
Why is the circadian system intolerant major alterations?
Biological clock becomes out of sync with outside world
Micheal Siffre
Isolated himself underground for months w/ no external cues
Only factor influencing behaviour was internal body clock, I.e his free running circadian rhythm
2 months = Southern alps, 6 months = Texan cave
Micheal siffre findings
Each case study, free running circadian rhythm settled to 25 hrs
Body kept to regular sleep/wake cycle w/o external cues
Micheal siffre research support
Aschoff and Wever
A03: research support Aschoff and wever
12 student volunteers in bunker with no natural light
All but one showed circadian rhythm of 24-25 hrs
Aschoff and wever study disadvantages
Small group of pp’s not representative of wider population
Influence of others impact results
Aschoff and wever: how did influence of others impact results?
Confirmed to majority when to eat/sleep which influence S/W cycle
A03: Siffre and Aschoff and wever. SO what?
Suggests research into S/W cycle is problematic
Siffre: influence of EZ (artificial light) - Czeiler altered pp’s rhythms from 22 to 28 hours using artificial light
Aschoff groups: influence of EZ (social cues: meal time)
A03: chronotherapeutics
Risk of heart attack is early in morning
Medication designed to take before bed but kick in at 6am - noon
What is chronotherapeutics?
Study of how timing affects drug treatments
A03: who found individual differences?
Duffy et al
A03: Duffy et al
Morning people rise and go to bed earlier 6am-10pm
Evening people ride and go to bed later 10am- 1am
A03: Duffy SO what?
Demonstrates innate individual differences in circadian rhythms
Suggests research should be wary of these differences in investigations
