endogenous pacemakers + exogenous zeitgebers Flashcards
(23 cards)
What are endogenous pacemakers?
Internal body clocks that regulate biological rhythms, like the SCN for the sleep/wake cycle.
What are exogenous zeitgebers?
External factors that entrain or affect our biological rhythms, such as light.
What is the sleep/wake cycle?
A daily biological rhythm influenced by variations in the environment, such as light and darkness.
Where is the suprachiasmatic nucleus (SCN) located?
In the hypothalamus, above the optic chiasm.
What does the SCN do?
Maintains circadian rhythms like the sleep/wake cycle and responds to light input.
What did DeCoursey et al. (2000) find in their chipmunk study?
Destroying the SCN disrupted sleep/wake cycles; most chipmunks died when returned to their habitat.
What did Ralph et al. (1990) show with mutant hamsters?
Transplanted SCN tissue transferred the donor’s 20-hour cycle to the recipient.
What is the role of the pineal gland in sleep?
Releases melatonin at night to promote sleep.
What is melatonin?
A hormone released by the pineal gland that induces sleep and is inhibited by light.
What is one limitation of SCN research?
It may obscure the influence of other body clocks (peripheral oscillators).
What did Damiola et al. (2000) show about liver rhythms?
Feeding patterns in mice can alter liver cell rhythms by 12 hours without disrupting SCN, suggesting more complex influences on sleep/wake cycle.
Why can’t endogenous pacemakers be studied in isolation?
In real life, endogenous pacemakers and exogenous zeitgebers interact.
What is an ethical issue in SCN animal studies?
Subjects like chipmunks were put at risk and many died post-study.
What is a zeitgeber?
A cue in the environment that resets our biological clock.
How does light affect the sleep/wake cycle?
It resets the SCN and influences hormone secretion and blood circulation.
What did Campbell and Murphy demonstrate with light?
Light shone on the knees altered participants’ sleep/wake cycle by up to 3 hours.
What role do social cues play in circadian rhythms?
They help entrain rhythms, e.g., meal and bedtime schedules affect babies’ sleep.
How does jet lag research support the role of social cues?
Adjusting to local time cues helps beat jet lag and align circadian rhythms.
What do environmental observations suggest about zeitgebers?
People in constant darkness/light maintain regular sleep patterns, suggesting internal control.
What did Laughton Miles et al. (1977) find?
A blind man had a 24.9-hour rhythm unaffected by social cues, highlighting their limited impact.
What happens to sleep quality with age?
It often worsens due to changes in circadian rhythm and melatonin levels.
What did Duffy et al. (2015) suggest about older adults?
They tend to sleep and wake earlier.
What did Hood et al. (2004) find about elderly light exposure?
Poor quality sleep in care homes may result from less exposure to natural light.
