Circadian Rhythms

Question 1

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

Answer 1

Zeitgeber (time giver)

Question 2

What happens to melatonin levels as per and Tim drop?

Answer 2

Melatonin increases

Question 3

What happens when an SCN of one animal is transplanted into another?

Answer 3

The pattern returns to normal in the form of the other animals rhythm

Question 4

How does jet lag impact professional sports teams?

Answer 4

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

Question 5

What does the suprachiasmatic nucleus (SCN) of the hypothalamus do in biological clocks?

Answer 5

It is the internal pacemaker that is the target of the retinohypothalamic tract

Question 6

Examples of circadian rhythms

Answer 6

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

Question 7

What do per and Tim inhibit?

Answer 7

Clock protein

Question 8

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

Answer 8

SCN of the hypothalamus

Question 9

What do melatonin signals do in seasonal rhythms?

Answer 9

Entrain circannual clock

Question 10

When does phase delay happen?

Answer 10

Westward travel

Question 11

Two types of jet lag

Answer 11

Phase advance and phase delay

Question 12

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

Answer 12

12-2am when per and Tim start to disintegrate

Question 13

When is growth hormone release high and low?

Answer 13

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

Question 14

Control morning activity and need light for entrainment

Answer 14

M cells

Question 15

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

Answer 15

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

Question 16

When does phase advance happen?

Answer 16

Eastward travel

Question 17

What type of phase shift is fall back?

Answer 17

Phase delay. Analogous to westward travel

Question 18

Humans our relationship to seasonal (circannual) rhythms

Answer 18

Equatorial animals, thus circadian rhythms dominate over circannual rhythms

Question 19

The process of resetting the biological clock

Answer 19

Entrainment

Question 20

What is shift maladaptation syndrome and who is it common in?

Answer 20

Sleep disorder caused by disruption of circadian rhythms and melatonin signaling. Common in people who work overnight shifts

Question 21

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

Answer 21

Seasonal rhythms

Question 22

GRAPHIC ON 8

Answer 22

GRAPHIC ON 8

Question 23

When is temperature high and low?

Answer 23

High = waking hours
Low = sleeping

Question 24

How do cortisol levels change throughout the day?

Answer 24

Highest in the morning and drop throughout the day

Question 25

How do circadian rhythms contribute to symptoms?

Answer 25

Some symptoms are worse at different times of the day

Question 26

What do the ganglion cells in the retinohypothalamic tract not rely on and what do they contain?

Answer 26

They don't rely on rods and cones and they contain the photopigment melanopsin (blue light)

Question 27

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

Answer 27

Circadian rhythms

Question 28

What releases melatonin?

Answer 28

Pineal gland

Question 29

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

Answer 29

Melanopsin

Question 30

Larks vs owls

Answer 30

``` Larks = morning people Owls = night people ```

Question 31

What is caffeine? What does it do postsynaptically?

Answer 31

Adenosine antagonist. Blocks adenosine receptors

Question 32

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

Answer 32

Phase shift

Question 33

Where are the pineal gland and SCN?

Answer 33

In the pathway of the retinohypothalamic tract

Question 34

What are some treatments for SAD?

Answer 34

Phototherapy and antidepressants (SSRIs)

Question 35

What type of phase shift is spring forward?

Answer 35

Phase advance. Analogous to eastward travel

Question 36

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

Answer 36

SAD

Question 37

What question should physicians ask related to circadian rhythms?

Answer 37

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

Question 38

What does free running cause?

Answer 38

Approximately 25 hour rhythm, sleep onset slightly later each day

Question 39

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

Answer 39

12-2am. Per and Tim disintegrate

Question 40

What does the activation of clock trigger?

Answer 40

The production of per and tim

Question 41

When do levels of per and Tim rise?

Answer 41

10:30 am - 12 pm

Question 42

What is intrinsic rhythmicity?

Answer 42

Rhythmic in the absence of inputs/outputs

Question 43

What does the night shift setting do?

Answer 43

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

Question 44

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

Answer 44

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

Question 45

What two groups of circadian neurons are in the SCN?

Answer 45

M cells and E cells

Question 46

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

Answer 46

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

Question 47

What does the SCN of the hypothalamus follow?

Answer 47

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

Question 48

Active during the daytime and sleep at night

Answer 48

Diurnal

Question 49

What happens with light entrainment in amphibians and birds?

Answer 49

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

Question 50

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

Answer 50

Dawn (7-8am) and they activate clock

Question 51

What does a lesion to the SCN cause?

Answer 51

Destroyed rhythm. No pattern

Question 52

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

Answer 52

Non-image forming

Question 53

What areas are more at risk for SAD?

Answer 53

Far north and south

Question 54

How can one system can throughout the day?

Answer 54

It can vary on many different levels

Question 55

The hormone of darkness

Answer 55

Melatonin

Question 56

Where is the SCN of the hypothalamus?

Answer 56

Above the optic chiam in the hypothalamus

Question 57

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

Answer 57

Suprachiasmatic nucleus of the hypothalamus (SCN)

Question 58

When is cortisol release high and low?

Answer 58

``` High = mornings and dropping throughout day Low = sleep ```

Question 59

What can a circadian rhythm do to other rhythms?

Answer 59

It can set them

Question 60

What does more exposure to light at night lead to?

Answer 60

A variety of negative effects

Question 61

No environmental cues like light (constant exposure to light)

Answer 61

Free running

Question 62

Inhibited clock activity, which decreases production of per and tim

Answer 62

High per and tim

Question 63

How are alertness and temperature related?

Answer 63

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

Question 64

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

Answer 64

Sleep disorders

Question 65

GRAPHS ON 37

Answer 65

GRAPHS on 37

Question 66

When are melatonin levels highest?

Answer 66

Sleep

Question 67

What does melatonin do?

Answer 67

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

Question 68

What releases growth hormone and when?

Answer 68

Pituitary gland during stage 3 and 4 deep sleep

Question 69

Control evening activity and need darkness for entrainment

Answer 69

E cells

Question 70

Active at night and sleep during the daytime

Answer 70

Nocturnal

Question 71

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

Answer 71

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

Question 72

What can be expressed within a single system?

Answer 72

Multiple rhythms

Question 73

What does the pineal gland do in biological clocks?

Answer 73

Releases melatonin in the dark

Question 74

What does the retinohypothalamic tract consist of?

Answer 74

Ganglion cells that project to the SCN

Question 75

What causes SAD?

Answer 75

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

Question 76

Example of a circadian rhythm setting other rhythms

Answer 76

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

Question 77

What does clock promote?

Answer 77

Production of per and tim

Question 78

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

Answer 78

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

Question 79

Increased clock activity, which triggers production of per and tim

Answer 79

Low per and tim

Question 80

What causes disruptions of circadian rhythms and melatonin signaling?

Answer 80

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

Question 81

What happens with light entrainment in mammals?

Answer 81

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