Biological rhythms: Influences on the sleep/wake cycle

Question 1

What are endogenous pacemakers?

Answer 1

The body’s biological clock

Question 2

What are exogenous zeitgebers?

Answer 2

The external factors affecting the body’s biological clock

Question 3

What is an example of an endogenous pacemaker?

Answer 3

The suprachiasmatic nucleus (SCN)

Question 4

What is the suprachiasmatic nucleus (SCN)?
Where is it located?
What is the suprachiasmatic nucleus’s function, that also explains why it is called the primary endogenous pacemaker?
How does the suprachiasmatic nucleus perform it’s function?

Answer 4

The suprachiasmatic nucleus (SCN) is a group of nerve cells, located in the hypothalamus in each hemisphere of the brain.

The SCN is known as the primary endogenous pacemaker and it’s main function is to maintain the circadian rhythm

The SCN maintains the circadian rhythm by receiving information about light from the optic chiasm and passes that information to the pineal gland. The pineal gland then increases production of melatonin, if there are low daylight levels

Question 5

The suprachiasmatic nucleus function is to maintain the circadian rhythm. How does the suprachiasmatic nucleus do this?
Outline the process:

Answer 5

The SCN receives information about daylight from the optic chiasm. The SCN then passes this information onto the pineal gland. The pineal gland then increases melatonin production, if the levels of daylight are low

Question 6

What is melatonin’s function within the body?

Answer 6

Melatonin reduces brain activity, which induces sleep

Question 7

What are exogenous zeitgebers factors on the sleep/wake cycle?
What are endogenous pacemakers factors on the sleep/wake cycle?

Answer 7

Exogenous zeitgebers are external changes in the environment

Endogenous pacemakers are the body’s internal clock

Question 8

What exogenous zeitgebers affect the sleep/wake cycle?

Answer 8

Light and social cues

Question 9

What affect does light have on the sleep/wake cycle?

Answer 9

Light has an impact upon the melatonin production in the penal gland, therefore affecting sleepiness/wakefulness

Question 10

What affect do social cues have on the sleep/wake cycle?

Answer 10

Our biological rhythms are entrained through social convention. We are influenced by the norms of people around us as to what time we wake and sleep

Question 11

Outline the research conducted into the impact of endogenous and exogenous factors by Campbell and Murphy:

Answer 11

Campbell and Murphy had 15 participants who were woken up at various times who had a light shone on the back of their knees before going back to sleep. The researchers managed to vary their sleep cycles up to three hours

Question 12

What did the research conducted into the impact of endogenous and exogenous factors by Campbell and Murphy show?

Answer 12

The research conducted showed that light is an important exogenous zeitgeber. Additionally it is not the eyes that act as a light receptor but the skin as well

Question 13

Outline the research conducted into the impact of endogenous and exogenous factors involving newly born babies:

Answer 13

Research into newly born babies found when babies were first born their sleep patterns were erratic. By 6 weeks, their circadian rhythms started and by about 16 weeks they tended to be in a routine

Question 14

What did the research conducted into the impact of endogenous and exogenous factors involving newly born babies show?

Answer 14

This research showed that social cues are an important exogenous zeitgeber because of the schedule imposed by the parents. The parents entrained the sleep/wake cycle by setting times for eating and sleeping

Question 15

Outline the research conducted into the impact of endogenous and exogenous factors involving people who live in artic regions:

Answer 15

Similar studies have been done on people who live in arctic regions (where the sun does not set in the summer) and still show show normal sleep/wake cycles

Question 16

What did the research conducted into the impact of endogenous and exogenous factors involving people whole live in artic regions?

Answer 16

These studies shown that there are occasions where exogenous zeitgebers such as light have little effect on our internal rhythms

Question 17

What is a potential conclusion you can write when asked a 16 marker question related to this topic?

Answer 17

It can be said that in real life, endogenous zeitgebers and endogenous pacemakers interact and thus it is wrong to separate them. Both are important influences on the circadian rhythm.

Question 18

Outline the research conducted into the impact of endogenous and exogenous factors by Miles et al:

Answer 18

Miles et al reported the story of a young man who was blind from birth with a circadian rhythm of 24.9hrs. Despite exposure to social cues, his sleep/wake cycle could not be adjusted, as a result he had to take sedatives at night and stimulants in the morning to keep to the pace of the 24hr world.

This shows social cues may not be as effective as some psychologists may think. This is because despite being arounding other people who had the normal sleep/wake cycle, the man remained uninfluenced.