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Circadian rhythm Flashcards

1
Q

what are the 3 rhythms and their length? give an example for each

A

ultradian rhythm: <20h. LH
circadian rhythm: 20 to 28h. melatonin, cortisol, body temperature,
infradian rhythm: >28h. prolactin

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2
Q

why is GH not considered to be secreted in a circadian rhythm?

A

because it is not controlled by something within the body (exogenous control)

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3
Q

what happens to body temperature circadian rhythm of someone travelling time zones?

A

it is dysregulated for a few days

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4
Q

what is masking?

A

when something (ex sleep, light, diet) prevents you from measuring the circadian rhythm

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5
Q

what can melatonin levels be masked by?

A

light cycle (light decreases melatonin levels)

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6
Q

what can core body temperature be masked by?

A

sleep

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7
Q

what 2 processes are involved in time-isolation protocol?

A

constant routine protocol and forced desynchrony protocol

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8
Q

what did michel siffre do?

A

when in a cave for months to test if he kept his circadian sleep-wake cycle

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9
Q

what is the mammalian central clock?

A

suprachiasmatic nucleus SCN of the hypothalamus

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10
Q

what are molecular clockworks based on?

A

feedback loops of specific genes

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11
Q

name a gene necessary for circadian rhythms

A

Bmal1

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12
Q

what are the characteristics of constant routine protocol? why?

A
  • sustained wakefulness
  • semi-recumbent posture, limited activity
  • dim light
  • hourly snacks
    -> to get rid of the most things that could mask or entertain circadian rhythm
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13
Q

describe the force desynchrony protocol

A

measuring the free-running period (biological rhythm) of human subjects by forcing them on a 20 or 28h light:day cycle

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14
Q

how long is human’s actual circadian rhythm?

A

a bit longer than 24h

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15
Q

what is the consequence of lesion to hamster SCN?

A

loose circadian rhythm

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16
Q

what happens when you graft the SCN of an animal with a 24h circadian rhythm into one with a 22h cycle?

A

the animal now has a 24h circadian rhythm

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17
Q

how do individual SCN neuron act isolated in a petri dish?

A

they have the same peak of activity every 24h

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18
Q

what is different between species with circadian rhythms?

A

clock genes

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19
Q

what are conserved features between species with circadian rhythms?

A

oscillating mRNAs, proteins or activity
and
autoregulatory feedback loops

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20
Q

name molecular clockwork genes

A

Per1, 2, 3
Cry1, 2

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21
Q

what is special about cry and per genes?

A

they repress their own expression

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22
Q

via what genes do Per and Cry genes auto-regulate their expression?

A

CLOCK and BMAL1 genes

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23
Q

what happens when you KO Bmal1 gene?

A

blunted Per 1 RNA expression and lost of circadian rhythm in activity

24
Q

where else other than SCN can we find clock cells?

A

other brain regions and peripheral tissues!

25
what is the first enzyme to be discovered to have an effect on circadian clock?
CKIE
26
what happened to tau mutant hamster (mutated CKIE)?
they had unstable PER proteins which decreased CLOCK/BMAL1 inhibition which changed the circadian rhythm
27
what was the length of heterozygous and homozygous tau mutant hamster?
hetero = 22h homo = 20h
28
name one thing that is crucial for setting up the pace of circadian rhythms
post-translational modifications of clock proteins
29
what mutation is found in Familial Advanced Sleep Phase Disorder (FASPD) families?
mutation in PER2 and CKIdelta genes
30
what happens to people with Familial Advanced Sleep Phase Disorder (FASPD)?
their circadian rhythms are earlier and shorter than everyone else (ex go to bed at 7pm)
31
give examples of health problems associated with shift work
circadian rhythm disruption, brain/mental health effects, sleep reduction, GI problems, increased risk for cancer, infertility, CVD
32
How do circadian clocks drive 24h rhythms in physiology and behaviour? (2 ways)
control at the molecular and physiological level
33
what is the difference between clock gene vs clock-controlled genes?
- clock genes are part of the clock and disrupt the circadian rhythm when mutated - clock-controlled genes are controlled by clock genes
34
give examples of clock genes
PER2, CRY, BMAL1
35
are clock-controlled genes always rhythmic?
no
36
name an example of a gene that is only clock-controlled in certain conditions
AVP is a clock-controlled gene in the SCN, but not in the SON
37
in what organ is there a lot of clock-controlled genes?
liver
38
what gland produces melatonin?
pineal gland
39
how is SCN signal sent to pineal gland?
via noradrenaline which is released in the pineal gland in rhythmic fashion
40
what enzyme is limited during the day and is required for melatonin secretion?
AANAT
41
how is melatonin made?
serotonin + AANAT -> n-acetylserotonin + HIOMT -> melatonin
42
what gland makes cortisol?
adrenal glands
43
what hormone sends the circadian rhythm signal to the adrenal glands?
ACTH pituitary hormone
44
how did they find out that adrenal cells have an clock behavior that's independent of SCN?
wild-type adrenal gland cells fluctuate in cortisol level over 12 hours. PER2/Cry1 KO cells do not.
45
how does the adrenal gland independently control corticosterone circadian rhythm?
gating according to the time of day: mice adrenals respond more strongly to ACTH in the evening than morning
46
what is homeostatic regulation?
response to feeding and fasting
47
what is FAA?
food anticipatory activity: increase in activity that predicts feeding
48
what regulates FAA?
fond-entrainable oscillator FEO
49
is SCN necessary for FAA?
no! FAA is still there even without SCN
50
name an example of processes that differ during the day vs night in the live
day: glycogen synthesis night: gluconeogenesis
51
circadian rhythm can regulation feeding time, but can feeding time also regulate circadian rhythms?
yes
52
changing feeding schedule affects clock genes in many organs and tissues except which one?
SCN
53
how is LH affected by clock genes?
LH surges always happen at day-night transition
54
what happens to LH secretion in ovariectomized hamsters?
they keep the circadian LH surge
55
how does LH have a circadian rhythm?
SCN sends signal to GnRH

ANAT322 (10 decks)

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