BIOLOGICAL
RHYTHMS…read more

SCN
Bodily rhythms are regulated by the body's
internal clock, the SCN (Suprachiasmatic
Nucleus). The SCN can be reset by
exogenous zietgbers or external factors
such as light, pheromones and food.…read more

Types of Biological
Rhythms
Circadian Rhythm- Sleep Wake Cycle- 24 Hours
Infradian Rhythms- Menstrual Cycle- More than
24 hours but less than a year.
Ultradian Rhythms- Sleep Staircase- Less than
24 Hours…read more

CIRCADIAN
RHYTHMS
A circadian rhythm takes place every 24
hours, such as the sleep-wake cycle.
Siffre- Case study of a man in a cave
Morgan- Study of when mutant SCNs
were transplanted into rats
Miles- Case study of a blind man.
Luce and Segal- Study into inhabitants of
the Artic Circle.…read more

Siffre
AO1
Case study of a man who spent 6 months in a cave,
absent from any natural light or sound
He did however have contact with the outside world through a
phone, an exercise bike and there was some artificial lighting.
His sleep wake cycle remained cyclical but lengthened to 25
hours, emphasising the importance of light in keeping a 24
hour cycle.
AO2
It was a case study so it lacked population validity as the
results cannot be generalised to anyone else. However in a
similar study by Reinberg when a young woman spent time in
a cave her cycle lengthened to 24.6 hours.
It did however have very high ecological validity.
Confounding variables- other factors such as temperature
and not just light may have had an influence. Also artificial
light was present so there was some form of light, we cannot
now if the effects would have been different if there had been…read more

Morgan
AO1
Hamsters were given mutant SCNS with shorter
cycles, that were transplanted in the brain
Hamsters adopted new shorter rhythm
Evidence for role of SCN as body clock. Also
location didn't matter suggesting SCN rely on
chemical signals
AO2
Ethical issues, cruel and unethical to conduct
brain experiments on animals.
Cannot generalise findings from animals studies
to humans, but this experiment could not be done…read more