Sleep-Wake Cycle - Endogenous Pacemakers + Exogenous Zeitgebers - Supporting Evidence

Question 1

name the studies which show the importance of endogenous pacemakers

Answer 1

DeCoursey et al’s chipmunks (2000)

Ralph et al’s hamsters (1990)

Question 2

name the studies which show the importance of exogenous zeitgebers

Answer 2

Campbell & Murphy - Knees (1998)

Potential role of social cues

Question 3

DeCoursey et al’s chipmunks (2000) - method

Answer 3

• Destroyed SCN connections in 30 chipmunks
• Returned them to the wild
• Observed for 30 days

Question 4

DeCoursey et al’s chipmunks (2000) - findings

Answer 4

Many killed by predators - w/o circadian rhythms, they were awake at wrong time

Question 5

Ralph et al’s hamsters (1990) - method

Answer 5

• Bred ‘mutant’ hamsters with 20 hrs

- Transplanted foetal SNC cells into brain of ‘normal’ hamster

Question 6

Ralph et al’s hamsters (1990) -findings

Answer 6

Previously ‘normal’ hamsters now chowed 20 hour cycle too

Supports SCN as an endogenous pacemaker

Question 7

Campbell & Murphy - Knees (1998) - method

Answer 7

Shone light in back if knees of Ps woken several times in the night

Question 8

Campbell & Murphy - Knees (1998) - findings

Answer 8

Some cycles changed - by up to 3 hrs

Showed light is important zeitgeber - doesn’t have to go through the eyes… Skin appears to be a receptor too

Question 9

Potential role of social cues - patenting

Answer 9

• Imposing meal times + bed times help to entrain the circadian rhythm
• Use black out lining in curtains to reinforce signals of light and dark in summer months

Question 10

Potential role of social cues - - jet lag

Answer 10

By using zeitgebers of a country you have travelled to, can adjust cycle so that it is synchronised to new time zone

Question 11

Potential role of social cues - - jet lag examples

Answer 11

• eat when the locals eat
• leave curtains open when you sleep so that the light (zeitgeber) can help entrain your circadian rhythm to new time zones