Endogenous Pacemakers And Exogenous Zietgeibers

Question 1

Separate rhythms:

Folkard (1996)

Answer 1

Under normal conditions the SCN coordinates all other bodily rhythms: however in some circumstances these rhythms can become out of sync with each other

F: studied a student who spent 25 days in a lab environment; she had no access to daylight or other zeitgebers that might have reset the SCN
Findings: by the end, her core temperature rhythm was still at 24 hours however her sleep wake cycle had extended to 30 hours

Question 2

The role of the SCN:

Skene and Arendt (2007)

Answer 2

The role of melanopsin can be found in studies of blind people: some blind people are still able to reliably entrain their circadian rhythm in response to light despite a total lack of image-forming visual perception

S&A: suggested that the pathway from retinal cells containing melanopsin to the SCN is still intact

Question 4

Using light exposure to avoid jet lag:

Burgess (2003)

Answer 4

B: found that exposure to BriteLite prior to 8 E. West flat D crease the time needed to re-adjust to local time on arrival

Participants were exposed to either continuous bright light or dim light; those exposed to continuous bright light shifted their circadian rhythm by 2.1 hours where as those exposed to dim light shifted there is by just 0.6 hours.

Thus, those in the first treatment felt sleepier two hours earlier and woke up two hours earlier in the morning - closer to the local time conditions prior to the journey

Question 6

The role of the SCN:

Morgan (1995)

Answer 6

bred a strain of hamsters so they had a circadian rhythm of 20hrs instead of 24

SCN nuerons from these abnormal hamsters were transplanted into the brains of normal hamsters

the normal hamsters then displayed the same abnormal circadian rhythm of 20 hours showing that the SCN had altered their brains

the same occurred for the reverse - normal SCN nuerons implanted in abnormal hamsters