Biological Rhythms - circadian rhythms Flashcards
Who is subject to biological rhythms?
All living things - important influence o way people behave
What two things are all biological rhythms governed by?
The bodies internal clock (endogenous pacemakers) and external change in the environment (exogenous pacemakers)
When do the rhythms occur?
Some occur many times during the day (ultradian rhythms), some take longer than a day (infradian rhythms) and in some cases much longer (circannual rhythms)
How long does a circadian rhythm last and what is an example?
About 24 hours e.g. the sleep/ wake cycle and core temperature
What is the sleep wake cycle?
We feel awake in the day and drowsy at night - this is the effect of daylight on the body - an important exogenous zeitgeber on our sleep/wake cycle
What would happen if the biological clock didn’t have the influence of external stimuli like light?
We wouldn’t know if it was day or night
Who is Siffre?
A self-styled cave man who spent several extended periods of time underground to study the effects on his own biological rhythms
what did Siffre find?
Deprived of exposure to natural light he resurfaced in mid September 1962 after 2 months in southern alp caves and believed it to be mid august
Decade later did it for 6 months and his free running biological rhythm settled down to one that was just beyond the usual 24 hours but he did sleep and wake up on a regular schedule
What was Aschoff and Wever’s research?
Convinced a group of participants to spend four weeks in a world war two bunker deprived of natural light - all but one of the participants displayed a circadian rhythm of 24-25 hours
What do the studies suggest?
That the natural sleep wake cycle may be a bit longer than 24 hours but as we are trained by exogenous zeitgebers associated with a 24 hour day such as sunlight and meal times
What was Folkard’s study?
Studied 12 people who agreed to live in a cave for three weeks, they agreed to go to bed when the clock said 11:45 and get up when it said 7;45. The researchers gradually quickened the clock so an apparent 24 hour day only lasted 22 hours - not one of the participants could fully adjust to the new regime
What did Folkard’s study suggest?
The existence of a strong free running circadian rhythm that cannot easily be overridden by changes in the external environment
What is core body temperature?
It varies by around 2 degrees during the course of the day - at its lowest around 4 in the morning (36) and peaks around six in the evening (38)
What does evidence suggest about body temperature?
It may have an effect on mental abilities - the warmer we are the better our cognitive performance
What was Folkard’s research into body temp?
Demonstrated how children who have stories told to them at 3pm have greater recall and comprehension after a week compared to children who heard the same stories at 9 am
