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PSYC 375 > Chapter 13_Circadian Rhythms > Flashcards

Chapter 13_Circadian Rhythms Flashcards

1
Q

Describe the features of the Earth’s rotation that result in days, years, and seasons.

A

Day: axial rotation
Year: orbit
Seasons: tilt of axis

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2
Q

When discussing biological rhythms in humans, we refer mostly to (daily/yearly/seasonal) variations.

A

daily

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3
Q

True or False? Circadian rhythms depend on sleep/wake times.

A

False

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4
Q

What are some examples of physiological parameters in humans that follow daily rhythms?

A 
Hormones secretion (cortisol, melatonin)
Body temperature
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5
Q

What are some examples of psychological parameters in humans that follow daily rhythms?

A

alertness, rxn time

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6
Q

In a typical biological human rhythm, melatonin is (high/low) when alertness is low.

A

high

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7
Q

What is the standard assay used to study rhythms in a lab setting?

A

running wheel connected to a computer

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8
Q

What is a measure used to assess biological rhythms in birds?

A

perch-hopping

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9
Q

What is the name of the output generated from a running wheel when studying rhythms in a lab setting?

A

actogram

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10
Q

Which class of biological rhythms occur more often than once a year but less often than once a day? Name an example of this rhythm.

A

infradian

e.g. estrus & menstrual cycles

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11
Q

What is BRAC? What class of biological rhythms does it belong to?

A

BRAC = Behavioural Rest and Activity Cycles

ultradian rhythm

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12
Q

How often do ultradian rhythms occur?

A

more than daily

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13
Q

What are rhythms that occur on a yearly basis termed?

A

circannual

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14
Q

What is the outcome when humans are placed in time-free environments?

A

a drift in rhythm (1 hour later each day) – period is >24 hours

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15
Q

If the the human circadian clock is running slow (>24 hours), then why do we exhibit 24 hour behaviour/physiology patterns?

A

response to environmental cycles; “clock” is “re-set” each day

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16
Q

What is the advantage of having a clock that doesn’t run at exactly 24 hours?

A

It permits the clock to track changing dawn/dusk times, as day length changes over the year (except at equator)

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17
Q

What is a zeitgeber? What are some examples?

A

gives info about time and synchronizes circadian clock

e.g. sunrise/sunset, social interaction, exercise, food

18
Q

What is the name of the process through which zeitgebers synchronize the circadian clock?

A

entrainment

19
Q

What is the most potent zeitberger?

A

light

20
Q

At what times is light the best cue? What effect does light have at these times?

A

early morning: nudge ahead

late evening: nudge back

21
Q

The deeper light falls into the night, the (smaller/greater) its effect.

A

greater

22
Q

The effect of light is maximal around (minimum/maximum) body temperature.

A

minimum

23
Q

Who was the first scientist to search for the location of the circadian clock?

A

Curt Richter

24
Q

How did Richter test the idea that activity was the “gear” of the the circadian clock? What were the findings?

A

He prevented activity for a week. The clock did not stop running, because activity resumed in line with previous pattern.
=> circadian clock is pacemaker

25
Q

If the circadian pacemaker does not drive behaviours directly, what does it control?

A

It regulates the activity of neural structures that control the behaviours.

26
Q

In Richter’s lesioning experiments, a lesion to the __________ disrupted rhythmicity.

A

anterior hypothalamus

27
Q

Which brain structure is the circadian clock likely localized to?

A

the suprachiasmatic nucleus (SCN)

28
Q

How is information about the light-dark cycle transmitted to the SCN?

A

retinal input

the retinohypothalamic pathway

29
Q

How did lesion studies show localization of the circadian pacemaker to the SCN?

A

when SCN was lesioned, animals became arrhythmic

30
Q

How did metabolic activity localize the circadian pacemaker to the SCN?

A

Animals were injected with radioactive 2-deoxyglucose. Cells take this up proportionally to their activity. The SCN is the only brain region that takes it up with a rhythm.

31
Q

What is the problem with using a lesioning approach to localize the circadian clock to the SCN?

A

the SCN could be a connection and not the endpoint of circadian rhythms

32
Q

How did studies of electrical activity show that circadian rhythms may originate from the SCN?

A

SCN has rhythm of electrical activity when recorded in animal.
When isolated in brain, SCN is still rhythmic but other areas are not.
When removed from brain, SCN continues to show rhythms in vitro.
Single cells within SCN are rhythmic.

33
Q

The clock mechanism in the SCN is (inter/intra)cellular. (How do we know?)

A

INTRAcellular

Single cells within SCN are rhythmic on their own

34
Q

What is the effect of electrical stimulation of SCN?

A

phase shifts that match those produced by light

35
Q

True or False? Chemical stimulation of the SCN affects the circadian clock.

A

True

36
Q

Imagine a scenario where a hamster is in free-running rhythm. A light pulse is provided near the start of its activity period. What occurs?

A

Phase delay (“nudge ahead”)

37
Q

A hamster is in free-running rhythm. A light pulse is provided, and a phase advance is observed. When was the light pulse probably provided?

A

End of activity cycle

38
Q

What are the lengths of cycles for Tau +/+, +/- and -/- hamsters?

A

+/+ 24 hrs
+/- 22 hrs
-/- 20 hrs

39
Q

What happens when a WT SCN is transplanted into a tau mutant hamster?

A

it adopts a 24 hour cycle

40
Q

Does the SCN exert effects on rhythmicity via neural or diffusible signals? How do we know?

A

Diffusible signals

Encapsulated SCN grafts sustain rhythmicity

41
Q

Which period gene is associated with delayed sleep phase insomnia in humans?

A

Period 3

42
Q

What are some circannual cycles controlled by melatonin secretion?

A 
gonad size (& sexual behaviour) 
coat colour

PSYC 375 (2 decks)

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