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ANAT322 > Circadian rhythm > Flashcards

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
Q

what is the first enzyme to be discovered to have an effect on circadian clock?

A

CKIE

26
Q

what happened to tau mutant hamster (mutated CKIE)?

A

they had unstable PER proteins which decreased CLOCK/BMAL1 inhibition which changed the circadian rhythm

27
Q

what was the length of heterozygous and homozygous tau mutant hamster?

A

hetero = 22h
homo = 20h

28
Q

name one thing that is crucial for setting up the pace of circadian rhythms

A

post-translational modifications of clock proteins

29
Q

what mutation is found in Familial Advanced Sleep Phase Disorder (FASPD) families?

A

mutation in PER2 and CKIdelta genes

30
Q

what happens to people with Familial Advanced Sleep Phase Disorder (FASPD)?

A

their circadian rhythms are earlier and shorter than everyone else (ex go to bed at 7pm)

31
Q

give examples of health problems associated with shift work

A

circadian rhythm disruption, brain/mental health effects, sleep reduction, GI problems, increased risk for cancer, infertility, CVD

32
Q

How do circadian clocks drive 24h rhythms in physiology and behaviour? (2 ways)

A

control at the molecular and physiological level

33
Q

what is the difference between clock gene vs clock-controlled genes?

A
  • clock genes are part of the clock and disrupt the circadian rhythm when mutated
  • clock-controlled genes are controlled by clock genes
34
Q

give examples of clock genes

A

PER2, CRY, BMAL1

35
Q

are clock-controlled genes always rhythmic?

A

no

36
Q

name an example of a gene that is only clock-controlled in certain conditions

A

AVP is a clock-controlled gene in the SCN, but not in the SON

37
Q

in what organ is there a lot of clock-controlled genes?

A

liver

38
Q

what gland produces melatonin?

A

pineal gland

39
Q

how is SCN signal sent to pineal gland?

A

via noradrenaline which is released in the pineal gland in rhythmic fashion

40
Q

what enzyme is limited during the day and is required for melatonin secretion?

A

AANAT

41
Q

how is melatonin made?

A

serotonin + AANAT -> n-acetylserotonin + HIOMT -> melatonin

42
Q

what gland makes cortisol?

A

adrenal glands

43
Q

what hormone sends the circadian rhythm signal to the adrenal glands?

A

ACTH pituitary hormone

44
Q

how did they find out that adrenal cells have an clock behavior that’s independent of SCN?

A

wild-type adrenal gland cells fluctuate in cortisol level over 12 hours.
PER2/Cry1 KO cells do not.

45
Q

how does the adrenal gland independently control corticosterone circadian rhythm?

A

gating according to the time of day: mice adrenals respond more strongly to ACTH in the evening than morning

46
Q

what is homeostatic regulation?

A

response to feeding and fasting

47
Q

what is FAA?

A

food anticipatory activity: increase in activity that predicts feeding

48
Q

what regulates FAA?

A

fond-entrainable oscillator FEO

49
Q

is SCN necessary for FAA?

A

no! FAA is still there even without SCN

50
Q

name an example of processes that differ during the day vs night in the live

A

day: glycogen synthesis
night: gluconeogenesis

51
Q

circadian rhythm can regulation feeding time, but can feeding time also regulate circadian rhythms?

A

yes

52
Q

changing feeding schedule affects clock genes in many organs and tissues except which one?

A

SCN

53
Q

how is LH affected by clock genes?

A

LH surges always happen at day-night transition

54
Q

what happens to LH secretion in ovariectomized hamsters?

A

they keep the circadian LH surge

55
Q

how does LH have a circadian rhythm?

A

SCN sends signal to GnRH

ANAT322 (10 decks)

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