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Flashcards in Circadian Rhythms Deck (81)
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1

External cue that synchronizes or helps entrain (determine or modify) an organisms internal clock

Zeitgeber (time giver)

2

What happens to melatonin levels as per and Tim drop?

Melatonin increases

3

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

4

How does jet lag impact professional sports teams?

Teams with phase advance jet lag were more likely to lose, make mistakes, commit fouls, etc.

5

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

6

Examples of circadian rhythms

Body temp (lower at night), cortisol secretion (high in the morning), activity levels, and sleep/wakefulness

7

What do per and Tim inhibit?

Clock protein

8

What is always more active during light periods in nocturnal and diurnal animals?

SCN of the hypothalamus

9

What do melatonin signals do in seasonal rhythms?

Entrain circannual clock

10

When does phase delay happen?

Westward travel

11

Two types of jet lag

Phase advance and phase delay

12

What time are peak melatonin levels? What else is going on?

12-2am when per and Tim start to disintegrate

13

When is growth hormone release high and low?

High = stage 3 and 4 deep sleep
Low = waking hours

14

Control morning activity and need light for entrainment

M cells

15

What backs up the fact that the SCN is a pacemaker?

Lesion studies, selective breeding, transplants, 24 and 20 hour hamsters

16

When does phase advance happen?

Eastward travel

17

What type of phase shift is fall back?

Phase delay. Analogous to westward travel

18

Humans our relationship to seasonal (circannual) rhythms

Equatorial animals, thus circadian rhythms dominate over circannual rhythms

19

The process of resetting the biological clock

Entrainment

20

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

21

An endogenous circannual clock, separate from the SCN but location unknown, runs at approximately 365 days

Seasonal rhythms

22

GRAPHIC ON 8

GRAPHIC ON 8

23

When is temperature high and low?

High = waking hours
Low = sleeping

24

How do cortisol levels change throughout the day?

Highest in the morning and drop throughout the day

25

How do circadian rhythms contribute to symptoms?

Some symptoms are worse at different times of the day

26

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)

27

Any rhythmic change that continues at close to a 24 hour cycle in the absence of 24 hour cues

Circadian rhythms

28

What releases melatonin?

Pineal gland

29

What do non-image receptor cells in the retinohypothalamic tract use?

Melanopsin

30

Larks vs owls

Larks = morning people
Owls = night people

31

What is caffeine? What does it do postsynaptically?

Adenosine antagonist. Blocks adenosine receptors

32

Shift in activity in response to a synchronizing stimulus like light or dark

Phase shift

33

Where are the pineal gland and SCN?

In the pathway of the retinohypothalamic tract

34

What are some treatments for SAD?

Phototherapy and antidepressants (SSRIs)

35

What type of phase shift is spring forward?

Phase advance. Analogous to eastward travel

36

A type of depression that results from insufficient amounts of daylight during winter months

SAD

37

What question should physicians ask related to circadian rhythms?

What time is it and how can it be related to symptoms

38

What does free running cause?

Approximately 25 hour rhythm, sleep onset slightly later each day

39

When do levels of per and Tim start to decrease and why?

12-2am. Per and Tim disintegrate

40

What does the activation of clock trigger?

The production of per and tim

41

When do levels of per and Tim rise?

10:30 am - 12 pm

42

What is intrinsic rhythmicity?

Rhythmic in the absence of inputs/outputs

43

What does the night shift setting do?

Improves the ability to sleep by making screens show more red light

44

What does the retinohypothalamic tract contain and what does it do in biological clocks?

Contains non-image receptor cells that use melanopsin to carry light info

45

What two groups of circadian neurons are in the SCN?

M cells and E cells

46

When are the highest levels of per and Tim and what does it cause?

7-9pm. Causes new production of per and Tim to stop

47

What does the SCN of the hypothalamus follow?

Being rhythmic in the absence of inputs/outputs (intrinsic rhythmicity). Follows about same 25 hour rhythm when free running

48

Active during the daytime and sleep at night

Diurnal

49

What happens with light entrainment in amphibians and birds?

They have translucent skulls and photoreceptors in the brain and pineal gland receive light directly

50

When are the lowest levels of per and Tim and what do they activate?

Dawn (7-8am) and they activate clock

51

What does a lesion to the SCN cause?

Destroyed rhythm. No pattern

52

What types of cells are the ganglion cells in the retionhypothalamic tract?

Non-image forming

53

What areas are more at risk for SAD?

Far north and south

54

How can one system can throughout the day?

It can vary on many different levels

55

The hormone of darkness

Melatonin

56

Where is the SCN of the hypothalamus?

Above the optic chiam in the hypothalamus

57

What is the mammalian master biological clock that is the pacemaker of circadian rhythms?

Suprachiasmatic nucleus of the hypothalamus (SCN)

58

When is cortisol release high and low?

High = mornings and dropping throughout day
Low = sleep

59

What can a circadian rhythm do to other rhythms?

It can set them

60

What does more exposure to light at night lead to?

A variety of negative effects

61

No environmental cues like light (constant exposure to light)

Free running

62

Inhibited clock activity, which decreases production of per and tim

High per and tim

63

How are alertness and temperature related?

They are positively correlated. They are high in waking hours and low in sleep

64

What can the disruption of circadian rhythms and melatonin signaling by unnatural zeitgebers cause?

Sleep disorders

65

GRAPHS ON 37

GRAPHS on 37

66

When are melatonin levels highest?

Sleep

67

What does melatonin do?

Opens the sleep gate but other systems must help us walk through it

68

What releases growth hormone and when?

Pituitary gland during stage 3 and 4 deep sleep

69

Control evening activity and need darkness for entrainment

E cells

70

Active at night and sleep during the daytime

Nocturnal

71

Is phase delay or phase advance easier to deal with and why?

Phase delay because it is easier to feel like you are going to bed later and waking up later than going to bed earlier and waking up earlier

72

What can be expressed within a single system?

Multiple rhythms

73

What does the pineal gland do in biological clocks?

Releases melatonin in the dark

74

What does the retinohypothalamic tract consist of?

Ganglion cells that project to the SCN

75

What causes SAD?

Overproduction of melatonin and lower levels of serotonin due to excessive reuptake

76

Example of a circadian rhythm setting other rhythms

Light info from photosensitive RGCs entrain the suprachiasmatic nucleus pacemaker. The pacemaker sets motor activity, eating, and body temp

77

What does clock promote?

Production of per and tim

78

What do high levels of per and Tim trigger and when?

They inhibit clock, resulting in decreased production of per and Tim. Around 3-430pm

79

Increased clock activity, which triggers production of per and tim

Low per and tim

80

What causes disruptions of circadian rhythms and melatonin signaling?

Unnatural zeitgebers like night shifts, jet lag, daylight savings time, cramming, and light pollution

81

What happens with light entrainment in mammals?

Light info goes from the eye to the SCN via retinohypothalamic pathway (starts in retina and goes to hypothalamus)