Circadian Rhythms

Question 1

What are circadian rhythms?

Answer 1

Biological rhythms that last 24 hours

Question 2

What is an example of circadian rhythms?

Answer 2

Sleep/wake cycle

Question 3

What is the first study of circadian rhythms?

Answer 3

Siffre. He spent 6 months in a cave with no natural light. He only had an artificial light to help him navigate

Question 4

What were the findings of Siffres study?

Answer 4

His sleep wake cycle settled to 25 to 30 hours

Question 5

What do the findings show from Siffres study?

Answer 5

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

Question 6

What is this the second study of circadian rhythms?

Answer 6

Aschoff and Wever. Participants lived in a bunker with no natural light

Question 7

What were the findings of Aschoff and Wevers study?

Answer 7

Their sleep/wake cycle was 25 to 27 hours

Question 8

What do the findings of Aschoff and Wever show?

Answer 8

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

Question 9

What is the third study of circadian rhythms?

Answer 9

Folkard et el. He withdrew participants from natural light for 3 weeks and changed the time cues to 22 hours a day

Question 10

What were the findings of Folkard et al study?

Answer 10

Only one participant out of twelve could not adjust to the shortened day

Question 11

What did the findings of Folkards et al study show?

Answer 11

Our natural circadian rhythm is flexible and can differ between individuals

Question 12

What are endogenous pacemakers?

Answer 12

Rhythms that are from internal bodily systems and can still function without the cues from the environment

Question 13

What is the main endogenous pacemaker?

Answer 13

The suprachiasmatic nucleus

Question 14

What does the suprachiasmatic nucleus do?

Answer 14

It is in the centre of the brain and it is regulated by light from the environment

Question 15

What is another endogenous pacemaker?

Answer 15

The pineal gland

Question 16

What does the pineal gland do?

Answer 16

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

Question 17

What is the first study of endogenous pacemakers?

Answer 17

Ralph et al. Removed the SCN out of genetically abnormal hamsters and transplanted it to normal rats

Question 18

What were the findings of Ralph et al study’s?

Answer 18

The circadian rhythms of the rats shortened to 20 hours

Question 19

What did the findings of Ralph et al study show?

Answer 19

The SCN is pivotal in regulating the internal body clock

Question 20

What was the second study on endogenous pacemakers?

Answer 20

Morgan. When the SCN was removed from normally functioning hamsters their circadian rhythms disappeared but returned when it was put back in

Question 21

What does Morgan’s study show?

Answer 21

The SCN is all important in the internal body clock

Question 22

What are exogenous zeitgebers?

Answer 22

They are cues from the environment that play an important role in regulating time and the circadian rhythm. For example sunlight and noise

Question 23

What is the first study on exogenous zeitgebers?

Answer 23

Campbell and Murphy. 15 volunteers slept in a lab and they were introduced to light during the night on the back of their knees

Question 24

What did the findings of Campbell and Murphy study show?

Answer 24

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

Question 25

What is the second study of exogenous zeitgebers?

Answer 25

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

Question 26

What do the findings of Shih-Yu Lee et al study show?

Answer 26

There are practical applications because zeitgebers can have positive effects in sleep quality

Question 27

What is the third study of exogenous zeitgebers?

Answer 27

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

Question 28

What did the findings of Steel et al study show?

Answer 28

Social cues did not have a strong effect in the absence of other zeitgebers eg light

Question 29

What can the disruption of circadian rhythms cause?

Answer 29

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

Question 30

What is a strength of EZ ad EP?

Answer 30

The research is important because it had helped to develop treatment methods

Question 31

What are three limitations of EZ and EP?

Answer 31

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