Endogenas Pacemakers and Exogenous Zeitgeber

Question 1

What is the SCN ?

Answer 1

• Receives information about light from the optic chiasm
• Happens even when eyes are closed
• Also known as the master pacemaker

Question 2

What does SCN stand for ?

Answer 2

suprachiasmatic nucleus

Question 3

How does the SCN process light ?

Answer 3

• SCN passes information about light to the pineal gland
• This gland releases melatonin which induces sleep during darkness
• Melatonin is inhibited during wakefulness

Question 4

What was Decoursey’s study on endogenas pacemakers ?

Answer 4

Method:
- Destroyed SCN connection of 30 chipmunks
- Returned chipmunks to their natural habitat
- Observed them for 80 days

Results:
- The sleep-wake cycle disappeared
- By the end a significant amount of chipmunks were dead
- Thought to be because they were awake at night when they were vulnerable to attack

Question 5

What was Ralph’s study of endogenas pacemakers ?

Answer 5

Method:
- Bred ‘mutant’ hamsters with a 20 hour sleep cycle
- Then they transplanted mutant SCN from fetus mutant hamsters into normal hamsters

Results:
- The normal hamsters defaulted to 20 hours
- Shows SCN is responsible/ control of the sleep-wake cycle

Question 6

What is another name for endogenas pacemakers ?

Answer 6

Internal bodyclock

Question 7

What are two examples of endogenas pacemakers ?

Answer 7

• SCN
• Pineal gland

Question 8

What does the SCN receive information about ?

Answer 8

• Light

Question 9

What does the pineal gland produce ?

Answer 9

Melatonin

Question 10

What are two examples of exogenous zeitgebers ?

Answer 10

• Light
• Social cues

Question 11

How is light an exogenous zeitgeber ?

Answer 11

• Syncs with the SCN
• pineal gland produces melatonin
• Integral
• Study from Campbell and Murphy

Question 12

What was the study that campbell and murphy did ?

Answer 12

• Looked at the effects of light
• Detected by skin receptors even when info isn’t received by the eyes
• participants were woken at various times and had a light pad shone on their knees
• caused deviation to some sleep-wake cycles by up to 3 hours

Question 13

How is social cues an exogenous Zeitgeber ?

Answer 13

• influence of other people can affect routines, bedtimes and mealtimes
• Routines entrain a sleep-wake cycle
• Can use the applicability of babies

Question 14

How can Sifre support exogenous zeitgebers ?

Answer 14

• He looked at how removing light through the caves affected someones sleep-wake cycle
• Found that it lengthened to 25-30 hours

Question 15

How do ethics limit endogenas pacemakers ?

Answer 15

• There was a lot of harm to these animals
• Need to look at the cost vs the benefit
• In this case there was little benefit as the animals have much simpler brains than us
• Means we can’t relate these studies to humans as our brains are structured differently
• Therefore an animals life was taken just for the evidence to lack generalisibility

Question 16

How does the interactionist system limit endogenas and exogenous ?

Answer 16

• Rather than looking at the two systems separately, it’s better to look at them together as they work hand in hand

Question 17

How does Mile’s study limit exogenous zeitgebers ?

Answer 17

• Study of a young man
• Blind from birth
• Had abnormal circadian rhythm for 24.9
• Despite exposure to social cues
• He couldn’t adjust his sleep-wake cycle
• Shows that social cues aren’t effective in resetting biological rhythms