Biological Rhythms and Biological Clocks Flashcards Preview

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Flashcards in Biological Rhythms and Biological Clocks Deck (44):
1

Biological rhythms

Any biological processes that repeat themselves at regular intervals

2

What is the name for rhythms << 24 hours?

Ultradian

3

What is the name for rhythms ~= 24 hours?

Daily

4

What is the name for rhythms >> 24 hours?

Infradian

5

What are the 4 "circa" rhythms?

- Circadian
- Circatidal
- Circalunar
- Circannual

6

What is the length of circadian rhythms?

24 hours

7

What is the length of circatidal rhythms?

12.5 hours

8

What is the length of circalunar rhythms?

29.5 days

9

What is the length of circannual rhythms?

~ 1 year

10

Is a circatidal rhythm ultradian or infradian?

Ultradian

11

Is a circalunar rhythm ultradian or infradian?

Infradian

12

Is a circannual rhythm ultradian or infradian?

Infradian

13

In the absence of external environmental cycles, the fact that circa rhythms persist has what 2 implications?

- That the rhythm must be generated by an internal, endogenous timekeeping device
- Signals from the environment somehow impact the biological clock, keeping it synced to the environmental cycle

14

How is it determined whether a daily rhythm is also circadian?

It must persist without ~ 24 hour environmental cycles (like light/dark)

15

Period (tau)

Duration of a cycle (equal to the wavelength)

16

Phase (phi)

A point on the cycle

17

How are the daily active and rest phases abbreviated?

Alpha and rho

18

Amplitude

The difference between the peak and trough of a rhythm, or between the peak and mean of the rhythm

19

Phase difference (psi)

The difference in time between two phases

20

Zeitgeber

Any periodic stimulus that can entrain a circadian rhythm

21

Zeitgeber time

External time (usually 24 hours)

22

Photoperiod

Duration of lights on

23

Scotoperiod

Duration of lights off

24

Are circadian rhythms "innate"? Why or why not?

Yes, because they do not require exposure to an environmental cycle in order to develop

25

What are two characteristics of "circa" rhythms?

- Under natural conditions, they are synchronized to major geophysical cycles in the environment
- Under artificial conditions, they persist within a period that approximates that of the corresponding geophysical environment

26

What is the name for animals that are primarily day active?

Diurnal

27

What is the name for animals that are primarily night active?

Nocturnal

28

What is the name for animals that are primarily dawn-and-dusk active?

Crepuscular

29

Oscillator

A device that produces a rhythm

30

Who coined the word "circadian"?

Franz Halberg

31

What are the possible explanations for the early appearance of circadian clocks?

- The need to shield certain biochemical processes from ionizing solar radiation
- Coordinating the activity of cellular antioxidant mechanisms with daily metabolic cycles
- The need to separate incompatible biochemical processes

32

What are the two primary functions of circadian clocks?

- Coordination of the organism with the outside work
- Coordination of internal biochemical and physiological processes

33

What type of organisms typically lack circadian rhythms of behaviour and sometimes lack circadian rhythms of gene expression?

Caverniculus organisms (cave dwelling)

34

Zeitgedächtnis

Time memory

35

Homeostasis

The regulation of vital physiological functions within certain optimal limits

36

What is the evidence that the source of circadian rhythms is endogenous and innate?

- Circadian rhythms persist in constant conditions, with a period usually slightly different from 24 hours
- Rhythms develop normally in the absence of external cycles
- Period differs within AND between species in same environment
- Period can be selected by breeding, altered by gene mutations, eliminated by gene knockout
- Period changes with age and internal hormonal state

37

What are the reasons for studying circadian rhythms?

- Understanding motivation
- Research design
- Neurobiology of time
- Behavioural ecology
- Shiftwork effects and solutions
- Sleep disorders
- Psychopathology
- Aging and dementia
- Medicine
- Interest

38

In IMAGE 1, what does each row represent?

A different variable

39

In IMAGE 1, what do the shaded areas represent?

Nighttime hours

40

In IMAGE 1, what does a dot on a horizontal line represent?

The time of day when the rhythm reaches its peak value

41

In IMAGE 1, what does the bar represent?

The standard deviation of the daily peak

42

In IMAGE 2, what is the chart called?

An actogram

43

In IMAGE 2, what does each line represent?

48 consecutive hours

44

Explain IMAGE 3

In the first 20 days, the subject is aware of time cues and goes to sleep at the same time each day, after the cues are removed (after day 21), their bedtime drifts by approx. 1.3 hours each day