Circadian Rhythms Flashcards
What are circadian rhythms?
Biological rhythms that last 24 hours
What is an example of circadian rhythms?
Sleep/wake cycle
What is the first study of circadian rhythms?
Siffre. He spent 6 months in a cave with no natural light. He only had an artificial light to help him navigate
What were the findings of Siffres study?
His sleep wake cycle settled to 25 to 30 hours
What do the findings show from Siffres study?
Internal mechanisms may control as the rhythm wasn’t too far from 24 hours but natural light is vital for keeping the cycle to 24 hours
What is this the second study of circadian rhythms?
Aschoff and Wever. Participants lived in a bunker with no natural light
What were the findings of Aschoff and Wevers study?
Their sleep/wake cycle was 25 to 27 hours
What do the findings of Aschoff and Wever show?
Rhythms could be controlled internally as the rhythms were not too far from the norm of 24 hours but that external factors play a part too as the rhythm was not exactly 24 hours as it should be
What is the third study of circadian rhythms?
Folkard et el. He withdrew participants from natural light for 3 weeks and changed the time cues to 22 hours a day
What were the findings of Folkard et al study?
Only one participant out of twelve could not adjust to the shortened day
What did the findings of Folkards et al study show?
Our natural circadian rhythm is flexible and can differ between individuals
What are endogenous pacemakers?
Rhythms that are from internal bodily systems and can still function without the cues from the environment
What is the main endogenous pacemaker?
The suprachiasmatic nucleus
What does the suprachiasmatic nucleus do?
It is in the centre of the brain and it is regulated by light from the environment
What is another endogenous pacemaker?
The pineal gland
What does the pineal gland do?
The SCN sends signals to the pineal gland which stimulates the release of the melatonin. When there is low light, high levels of melatonin are released which induces sleep, reduces serotonin, so the nervous system slows and brain activity falls
What is the first study of endogenous pacemakers?
Ralph et al. Removed the SCN out of genetically abnormal hamsters and transplanted it to normal rats
What were the findings of Ralph et al study’s?
The circadian rhythms of the rats shortened to 20 hours
What did the findings of Ralph et al study show?
The SCN is pivotal in regulating the internal body clock
What was the second study on endogenous pacemakers?
Morgan. When the SCN was removed from normally functioning hamsters their circadian rhythms disappeared but returned when it was put back in
What does Morgan’s study show?
The SCN is all important in the internal body clock
What are exogenous zeitgebers?
They are cues from the environment that play an important role in regulating time and the circadian rhythm. For example sunlight and noise
What is the first study on exogenous zeitgebers?
Campbell and Murphy. 15 volunteers slept in a lab and they were introduced to light during the night on the back of their knees
What did the findings of Campbell and Murphy study show?
It shows the importance of light on the sleep/wake pattern and it’s not necessary for light to just enter the eyes to have physiological effects
What is the second study of exogenous zeitgebers?
Shin-Yu Lee et al found that light therapy can help mothers with babies in intensive care which has low lighting. It can help their sleep quality
What do the findings of Shih-Yu Lee et al study show?
There are practical applications because zeitgebers can have positive effects in sleep quality
What is the third study of exogenous zeitgebers?
Steel et al. He monitored 6 participants in constant daylight in the Arctic for 6 weeks and they were asked to keep sleep logs. 5 out of 6 of the participants developed cycles longer than 24 hours
What did the findings of Steel et al study show?
Social cues did not have a strong effect in the absence of other zeitgebers eg light
What can the disruption of circadian rhythms cause?
Normally the EP and EZ are in synch with each other but with jet lag and shift work cause them to become unsynchronised.
Jet lag- body clock tells you to be asleep but the EZ tell you to be awake
Shift work- EP at night telling you to sleep but the EZ being on a night shift tells you to be awake
What is a strength of EZ ad EP?
The research is important because it had helped to develop treatment methods
What are three limitations of EZ and EP?
It has small samples and it is done in artificial conditions, it was not a normal nights sleep as it was in a lab and a lot of the research was done on animals
