Ultraradian Rhythms Flashcards
What is the suprachiasmatic nucleus (SCN)?
A tiny bundle of nerve cells located in the hypothalamus that regulates circadian rhythms such as the sleep/wake cycle
The SCN receives light information directly from the optic chiasm, influencing biological clock adjustments.
Where is the SCN located in the brain?
In the hypothalamus, just above the optic chiasm
‘Supra’ means ‘above’, indicating its position relative to the optic chiasm.
What happens to chipmunks when SC connections are destroyed?
Their sleep/wake cycle disappears, leading to increased vulnerability to predators
This was observed in a study by Patricia DeCoursey et al. (2000) over 80 days.
What was significant about the study involving mutant hamsters by Martin Ralph et al. (1990)?
Normal hamsters’ sleep/wake cycles defaulted to 20 hours when SC cells from mutant hamsters were transplanted
This indicates the SC’s critical role in regulating circadian rhythms.
What role does the pineal gland play in the sleep/wake cycle?
It produces melatonin, which induces sleep and is inhibited during wakefulness
The pineal gland receives light information from the SCN.
What is melatonin?
A chemical produced by the pineal gland that induces sleep
It is suggested as a causal factor in seasonal affective disorder.
What does the German word ‘zeitgeber’ mean?
‘Time giver’
Exogenous zeitgebers are external factors that reset biological clocks.
What is the role of light as an exogenous zeitgeber?
It resets the SCN and influences the sleep/wake cycle
Light can affect hormone secretion and blood circulation.
How was light shown to affect the sleep/wake cycle in the study by Scott Campbell and Patricia Murphy (1998)?
Light applied to skin receptors altered participants’ sleep/wake cycles by up to three hours
This indicates that light can influence the biological clock without being perceived by the eyes.
How do social cues affect infants’ sleep/wake cycles?
Infants’ rhythms begin to align with parental schedules around 16 weeks of age
Newborns initially have random sleep/wake cycles.
What is a recommended method for overcoming jet lag?
Adapting to local eating and sleeping times instead of personal feelings of hunger and fatigue
This method can help entrain circadian rhythms during long-distance travel.
