Endogenous Pacemakers and Exogenous Zeitgebers

Question 1

What are endogenous pacemakers?

Answer 1

Internal body clocks that regulate biological rhythm

Question 2

What is the superchiasmatic nucleus (SCN)?

Answer 2

Bundle of nerve cells

Question 3

Where is the SCN located?

Answer 3

Hypothalamus

Question 4

What is the SCN linked with?

Answer 4

The sleep/wake cycle

Question 5

What is the SCN connected to?

Answer 5

Optic chiasm

Question 6

What does the SCN receive?

Answer 6

Light directly when the eyes are closed

Question 7

Which two psychologist researched into the sleep/wake cycle?

Answer 7

• Decoursey et al

- Ralph et al

Question 8

What did Decoursey et al (2002) do?

Answer 8

• Destroyed SCN connection in 30 chipmunks

- Returned them to natural habit and observed

Question 9

What did Decoursey et al (2000) find?

Answer 9

Sleep/wake cycle disappeared and majority killed after 80 days

Question 10

What did Ralph et al (1990) do?

Answer 10

• Bred hamsters with 20 hour sleep/wake cycle

- SCN of mutant hamsters transplanted into normal hamsters

Question 11

What did Ralph et al (1990) find?

Answer 11

Normal hamsters developed a 20 hour sleep/wake cycle

Question 12

What is the SNC an example of?

Answer 12

Endogenous pacemaker

Question 13

What are the three examples of endogenous pacemaker?

Answer 13

• SCN
• Pineal gland
• Melatonin

Question 14

How is SCN linked to the pineal gland and melatonin?

Answer 14

SCN passes information on day length to pineal gland which increases secretion of melatonin during the night

Question 15

What does melatonin induce?

Answer 15

Sleep

Question 16

When is melatonin inhibit?

Answer 16

During periods of wakefulness

Question 17

What are the different factors which influence the sleep/wake cycle?

Answer 17

• Endogenous pacemakers

- Exogenous zeitgebers

Question 18

What are exogenous zeitgebers?

Answer 18

External cue which may affect biological rhythm i.e reset the biological clock

Question 19

What is the resetting of the biological clock is a process known as?

Answer 19

Entrainment

Question 20

What important exogenous zeitgebers are involved in the sleep/wake cycle?

Answer 20

• Light

- Social cues

Question 21

Who studied into the effect of light on the sleep/wake cycle?

Answer 21

Campbell and Murphy (1998)

Question 22

What did Campbell and Murphy (1998) do?

Answer 22

• Woke 15 participants at various times

- Shone a light on backs of their knee

Question 23

Why did Campbell and Murphy (1998) shine a light on the backs of their participants knees?

Answer 23

Produces a deviation in the sleep/wake cycle

Question 24

Does the detection of light just occur by the SCN?

Answer 24

No - skin receptors can also detect light

Question 25

How has social cues shown to be an important influence on sleep/wake cycle?

Answer 25

- Babies have set schedules can set sleep/wake cycle (normally really random in newborns) - Adapting to local time when travelling for eating and sleeping resets circadian rhythm (tackles jet lag)

Question 26

Is SCN the only endogenous pacemaker?

Answer 26

No

Question 27

What are other endogenous pacemakers?

Answer 27

- Lungs - Liver - Skin - Pancreas

Question 28

Why is studies into SCN limiting?

Answer 28

As ignores the important and the independence of the effects of other endogenous pacemakers

Question 29

Who showed the independence of the liver to the SCN?

Answer 29

Damiola et al (2000)

Question 30

What did Damiola et al (2000) find?

Answer 30

That altering feeding pattern altered circadian rhythm of the liver of up to 12 hours

Question 31

Are you able to generalise animal studies to humans?

Answer 31

No

Question 32

What are the issues when studying SCN and animal studies?

Answer 32

- Ethical issues | - Great harm and potential risk when returned back to habitat

Question 33

How may the influence of exogenous zeitbegebers be overstated?

Answer 33

People who are born bind show normal sleep/wake cycle, only needed to take sedatives in the morning to align with 24-hour world (Miles et al. 1977)

Question 34

What was a limitation to Campbell and Murphy (1998) method?

Answer 34

- Hasn't been replicated | - Some light exposure to participants eyes (confounding variables)

Question 35

What may studies have ignored when studying into exogenous zeitebegers?

Answer 35

How different exogenous zeitbegers interact and influence the sleep/wake cycle (reductionist)

Question 36

What is the collective problem between the research in to exogenous zeitebegers and endogenous pacemakers?

Answer 36

- That it is hard to separate the two when conducting research into just one - Why do researchers try to separate the two functions when they work together