w3) intro to c.rhythms Flashcards by Amanda Chiu

circadian rhythm is a what type of rhythm? how many hrs?

biological
24 hr roughly

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characteristic of clock

endogenous
passive or not passive?
not using what stimulus?

generated WITHIN individual
not passive
not using light or dark

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exogenous
examples?

generated OUTSIDE of indivudal
external cycles, influences- beahvior, light intensity, posture, sleep/wake rhythm

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characteristic of clock

free running period is what type of rhythm?

close/approx to 24 hr cycle

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characteristic of clock

settable?

synchronize- able,
can train to cyclic env
ex: light cycle set to 24 hrs

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characteristic of clock

innate

genetically coded

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4 characteristics of clocks?

endogenous
free running period
settable
innate

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tau is the length of ? also called the p?

length of ENDOGENOU RHYTHM (DD/LL)
called the period of rhythm

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tau

A free running tau/period is how many hours?

not 24 hrs
can be 23.5 hrs - faster than 24 earlier running each day
can be 24.5 hrs - slower than 24 later running each day

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LONGER tau/period (ex: 24.5 hrs) takes faster/longer time to allign back to phase?

FASTER (days)

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SHORTER tau/period (ex: 23.5 hrs) takes faster/longer time to allign back to phase?

LONGER (months)

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how is the clock “settable”? What can be changed?
What are 2 ways to change it?

tau can be changed - reset clock
can make a non-24 hr clock (free running) –> match/reset back to 24 hr

1) change period - speed up 24.6 hr /slow down 23.5 hr
2) reset phase - move back the clock 1:05 to 1:00

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if a circle = a complete cycle
phase represents what in the circle?

? in time
also called o?

specific point in the circle
single point in time
oscillation

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phase shift moves from ? to ?
example: phase advance and delay

moves from 1 time point/oscillation to another time
ex: 9:00 pm melbourne –> phase shift to hk 3 hrs behind –> phase delay 6:00 pm

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phase angle is the difference between?
example?

reference point on oscillator/phase time #1 vs #2

melatonin onset relative to sleep onset

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DD vs LL

constant darkness
constant lightness

tau is ? of the rhythm? length of endogenous DD/LL

period of the rhythm
length of endogenous DD or LL

for tau

hiding in a cave, no light for a long period, clock will change tau to ? hours

more night/darkness DD –> tau runs MORE THAN 24 HRS
ex: 24.2 hrs

for tau

morning person, waking up early to light exposure, clock will change tau to ? hours

more light LL –> tau runs LESS THAN 24 HRS
ex: 23.7 hrs

zeitgeber
gives ?

time giver (usually gives light cycle)

circadian time CT vs zeitbgeber time ZT?

both are ? points

both reference points
“inner day” activity onset, internal time
“outer day” light cycle on/off

ZT lights on/day time is #
ZT lights off/night time is #

0-12
12-24

phase delay (shift)

Is it for schedules more or less than 24 hrs?
add/subtract hrs?
black horizontal bars shift LEFT/RIGHT?
ex: rodent will start spinning activity later or earlier than previous time?

less than 24 hrs (ex: 23.5)
want to add hours
shift RIGHT
run LATER, think later mornings

phase delay (shift)

Does the clock hand go clockwise/anticlockwise?
think CT0, CT6, CT12, CT18
ex: we want to move from CT 18 to?

is it first 1/2 or second 1/2 of night?

anticlockwise - delaying, slowing down
ex: CT18 to CT16 (delay 2 hrs)

first half of night

# phase delay (shift) what type light exposure? 4 practices? | hint: think need to be awake for later hours,

evening light exposure (sunset walks) strategic naps diet, exericse, caffeine

# phase advance (shift) Is it for schedules more or less than 24 hrs? add/subtract hrs? black horizontal bars shift LEFT/RIGHT? ex: rodent will start spinning activity later or earlier than previous time?

more than 24 hrs (ex: 24.7 hrs) want to subtract hours bars shift LEFT rodent start spinning EARLIER mornings

# phase advance (shift) Does the clock hand go clockwise/anticlockwise? think CT0, CT6, CT12, CT18 ex: we want to move from CT 20 to? is it first 1/2 or second 1/2 of night?

clockwise- shift faster speeding up CT20 to CT 22 second 1/2 of night

# phase advance (shift) what type light exposure? 4 practices?

early light exposure (early morning surise dawn light walks) less naps, shift to earlier bed time slowly, avoid caffeine

# phase angle what are 2 ways to alter phase angle of entrainment?

change circadian period change system sensitivity to light

do women have advanced/delayed phase? less or more melatonin? insomnia? than men

ADVANCED phase wake up earlier LESS melatonin MORE insomnia trouble falling asleep, wakes earlier

# PRC phase response curve 4 main parts of PRC 1) straight line = 2) regions of stable entrainment ? 3) inc line 4) limits of entrainment is ?

dead zone regions of stable entrainment forbidden zone - shift from max delays to max advances limits - ranges from -2 to +3 hrs show max adjustment for delays/advances to sync to

Bees have their own language to tell other bees how to find the location of food. How does the circadian clock play a role?

Bees do a different intensity of “waggle dance” at different times of day, indicating where food will be available by the intensity

# You have a hamster running on a wheel in constant darkness. You wish for You have a hamster running on a wheel in constant darkness. You wish for the animal to run earlier the next day. What could you do to make the hamster run earlier tomorrow? A) Give a melatonin injection in the middle of the night B) Give a light pulse around nocturnal activity onset C) Give access to a novel running wheel in the night D) Give a light pulse close to the end of nocturnal activity

D) Give a light pulse close to the end of nocturnal activity

Which of the following schedules of light (L) and dark (D) in a 24 hour period would cause a long day plant to flower? A) 5L:5D:1L:13D B) 10L:14D C) 6L:8D:1L:9D D) Two of the above

C) 6L:8D:1L:9D

What key feature of a circadian clock was demonstrated by the opening and closing of plant leaves in constant light conditions? a. It is innate b. It is endogenous c. It is temperature compensated d. It is settable

b. It is endogenous

You have a hamster running on a wheel in constant darkness. You wish for the animal to run earlier the next day. What could you do to make the hamster run earlier tomorrow? a. Give a light pulse close to the end of nocturnal activity b. Give access to a novel running wheel in the night c. Give a light pulse around nocturnal activity onset d. Give a melatonin injection in the middle of the night

a. Give a light pulse close to the end of nocturnal activity

If you put a hamster in a running wheel in the middle of the day (the inactive time of day for a nocturnal animal), what will likely happen on the next day? a. It will run less later that night b. It will start running later (delay) c. It will become arrhythmic (disrupted clock) d. It will start running earlier (advance)

d. It will start running earlier (advance)

Which of the following is a more modern purpose (not an ancient purpose) of circadian rhythms? a. Organisation of physiological processes b. Seasonal behaviour (e.g., determining mating seasons) c. To maintain a constant body temperature, despite environmental changes d. Anticipation of environmental events

b. Seasonal behaviour (e.g., determining mating seasons)