S - Circadian/Biological Rhythms Flashcards
What is the superchiasmatic nucleus?
Tiny cluster of nerve cells which is the main endogenous pacemaker in mammals, located in the hypothalamus just above the optic chiasm
What does the SCN do to control the sleep-wake cycle?
The SCN then sends a message to the pineal gland to increase melatonin - this inhibits the brain mechanisms that control wakefulness
SCN is also effected by exogenous zeitgebers (e.g. light) - the retina sees the light and a message is sent along the retinohypothalmic tract
What is entrainment/how does it work?
The process of the sun and light working together to reset the sleep cycle
When the light starts to fade, a message is sent along the retinohypothalmic tract which connects the retina to the SCN. The SCN then sends a message to the pineal gland to increase melatonin - this inhibits the brain mechanisms that control wakefulness
What is a circadian rhythm?
Occurs once every 24 hours
What did morgan find?
Removed SCN from hamsters - circadian rhythm disappeared - no rhythm without SCN
What is a weakness of Morgan’s study?
Animal study - not generalisable
What did Schochat et al find?
Found period of greatest sleep propensity occurred just after melatonin secretion
What is a weakness of Schochat et al’s study?
Lacks ecological validity - lab study
Lacks population validity - small sample (6pps)
What did Campbell and Murphy find?
Participants given regular light exposure on the back of their knees, caused changes in their biological rhythms in line with the light/dark they were exposed ti
What is a weakness of Campbell and Murphy’s study?
No explanatory power as it doesn’t explain how information would get to the SCN
What did Folkhard find?
Participants lived in a cave for 12 weeks, researchers quickened the clock the followed to 22 hours, volunteers cycle stayed at 24 hours - SCN overruled clock
What did Miles et al find that goes against Folkhard?
Studied blind man from birth, had a strong 24.9 hour circadian rhythm, struggles resetting biological rhythms, has to take sedatives - shows that you cannot reset your body clock naturally without the use of light
