Flashcards in Circadian Rhythms Deck (81)
External cue that synchronizes or helps entrain (determine or modify) an organisms internal clock
Zeitgeber (time giver)
What happens to melatonin levels as per and Tim drop?
What happens when an SCN of one animal is transplanted into another?
The pattern returns to normal in the form of the other animals rhythm
How does jet lag impact professional sports teams?
Teams with phase advance jet lag were more likely to lose, make mistakes, commit fouls, etc.
What does the suprachiasmatic nucleus (SCN) of the hypothalamus do in biological clocks?
It is the internal pacemaker that is the target of the retinohypothalamic tract
Examples of circadian rhythms
Body temp (lower at night), cortisol secretion (high in the morning), activity levels, and sleep/wakefulness
What do per and Tim inhibit?
What is always more active during light periods in nocturnal and diurnal animals?
SCN of the hypothalamus
What do melatonin signals do in seasonal rhythms?
Entrain circannual clock
When does phase delay happen?
Two types of jet lag
Phase advance and phase delay
What time are peak melatonin levels? What else is going on?
12-2am when per and Tim start to disintegrate
When is growth hormone release high and low?
High = stage 3 and 4 deep sleep
Low = waking hours
Control morning activity and need light for entrainment
What backs up the fact that the SCN is a pacemaker?
Lesion studies, selective breeding, transplants, 24 and 20 hour hamsters
When does phase advance happen?
What type of phase shift is fall back?
Phase delay. Analogous to westward travel
Humans our relationship to seasonal (circannual) rhythms
Equatorial animals, thus circadian rhythms dominate over circannual rhythms
The process of resetting the biological clock
What is shift maladaptation syndrome and who is it common in?
Sleep disorder caused by disruption of circadian rhythms and melatonin signaling. Common in people who work overnight shifts
An endogenous circannual clock, separate from the SCN but location unknown, runs at approximately 365 days
GRAPHIC ON 8
GRAPHIC ON 8
When is temperature high and low?
High = waking hours
Low = sleeping
How do cortisol levels change throughout the day?
Highest in the morning and drop throughout the day
How do circadian rhythms contribute to symptoms?
Some symptoms are worse at different times of the day
What do the ganglion cells in the retinohypothalamic tract not rely on and what do they contain?
They don't rely on rods and cones and they contain the photopigment melanopsin (blue light)
Any rhythmic change that continues at close to a 24 hour cycle in the absence of 24 hour cues
What releases melatonin?
What do non-image receptor cells in the retinohypothalamic tract use?