Biological rhythms: Circadian Flashcards
How long does a Circadian rhythm ?
24 hour cycle
What is a biological rhythm ?
- Distinct patterns of change in body activity that conform to cyclical time periods
- Influenced by internal body clocks as well as external environmental changes
How long does an infradian cycle last ?
Longer than 24 hours
How long does a ultradian rhythm last ?
Shorter than 24 hours
What is an internal factor known as ?
Endogenas pacemaker
(body clock)
What is an external factor known as ?
Exogenous Zeitgebers
Time givers
What is a Circadian rhythm ?
- the cycle repeats itself over a 24 hours period
- Driven by body clock, found in our cells and synchronised by the master pacemaker (SCN)
-Syncs the body with the outside world
What was Sifre’s study ?
- Free running study
- Case of a French man
- Spent 6 months in a cave with no natural lighting or cues for the day
- When he woke up he used artificial light to navigate the cave
- Body clock went into a 25-30 hour sleep wake cycle
- Lost tracks of days : Though he’d been there for a month but was actually there for 179 days
- Shows that the sleepwake cycle is entrained by exogenous zeitgebers
What are evaluation of Sifre’s study ?
- small sample size - makes it difficult to generalise
- Cofounding variables - validity with artificial light
- Interaction between Endogenas Pacemaker and Exogenous Zeitgebers - doesn’t reflect daily life
What was Aschoff + Rutger’s study ?
Methods: A group of participants to spend 4 weeks in a bunker with no natural lighting
Results: All but one of the participants displayed circadian rhythms which were between 24-25 hours
Results mean: The natural sleep-wake cycle may actually be slightly longer but is entrained by exogenous zeitgebers such as meal times, daylight hours etc.
What was Folkard’s study ?
Method: 12 people agreed to live in a cave for 3 weeks. They went to bed when the clock turned 11:45 and woke at 7:45, the researchers sped the clock so it was a 22 hour day without participants knowing.
Results: Only one participant was able to comfortably adjust to this time change
Results show: Our sleep-wake cycle naturally wants longer rather than shorter
How does practical application evaluate sleep-wake studies ?
Shift work =
- leads to desynchronisation, accidents at work etc
- Research helps people to adapt
- Helps economy - maximises productivity
How do individual differences evaluate sleep-wake studies ?
- All these studies are on a small scale
- Sleep-wake scales massively depending on person
- Some people are more like larks and some are more like owls (Duffy)
