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Animal Behaviour > Sleep and Biological Rhythms > Flashcards

Sleep and Biological Rhythms Flashcards

1
Q

How is sleep defined? (simple)

A

A normal absence of consciousness

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2
Q

What does Siegel’s definition of sleep include? (3)

A

Rapidly reversible
Reduced sensory responsiveness
Homeostatically regulated - lost sleep increases drive for ‘sleep rebound’

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3
Q

Reasons for sleep? (4)

A

Energy conservation
Growth and repair
Metabolic clearance
Learning and memory

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4
Q

How does sleep vary across organisms/time?

A

Need decreases with age
Larger organisms tend to sleep for longer
Smaller sleep in bouts
Patterns change e.g. newborns also may sleep in bouts

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5
Q

Ecological influences of sleep? (4)

A

Predation risk suppresses
Thermoregulation suppresses
Foraging for food suppresses
Swimming suppresses e.g. dolphins 1/2 a brain at a time to breath at the surface

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6
Q

Intrinsic influences on sleep? (3)

A

Memory consolidation increases
Energy conservation
Metabolic clearance (byproducts accumulate in wakefulness)

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7
Q

Sleep stages?

A

Awake
Stage 1, 2, 3, 4
REM

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8
Q

Brain waves of each sleep stage?

A 
Awake - alpha, beta (=alertness)
1 - theta
2 - sleep spindles form, slow waves
3, 4 - slow waves, delta activity
REM - theta and beta (resembles awake)
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9
Q

Sleep cycles?

A

Around 5 per night, with deep sleep (stage 4) only in first 2.
Around 90 minutes in humans

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10
Q

Homeostasis in sleep?

A

Cycle with homeostatic sleep pressure and internal circadian clock -internal clock pushes past need to sleep until homeostasis kicks in in the evening

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11
Q

Neural systems of sleep? (2)

A

Forebrain systems - support SWS

Brainstem - activates forebrain for waking, triggers REM

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12
Q

What is the ascending arousal system?

A

Neural system in rats to govern sleep

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13
Q

Role of orexin?

A

In sleep - peptide secreted by neurons in lateral hypothalamus and stimulates feeding, related to wakefulness.
Orexin knockouts destroy bout-sleeping in rats and cause narcolepsy like symptoms

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14
Q

Symptoms of orexin knockouts? (4)

A 
Narcolepsy-like;
Sleep attacks in the day
Cataplexy (weakness after strong emotion)
Sleep paralysis
Hypnagogic hallucinations
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15
Q

What is unihemispheric sleep (USWS) and where is it found?

A

Sleeping with on side of the brain - seen in aquatic mammals and fish

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16
Q

Unihemispheric sleep in ducks?

A

Sleep with one eye open, brain hemisphere on opposite side awake.
Used where there is high predation risk, and often seen depending on location in group i.e. outer edges

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17
Q

USWS in frigate birds?

A

Large, making long flight trips up to 3000km over water

When flying, they spiral up thermals and glide straight down - USWS associated with the spiralling up, where the same brain side as direction of turn sleeps so they can still see other birds to avoid them.

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18
Q

Sleep in reptiles?

A

More rapid REM/NREM cycle than mammals/birds - 80s in Australian dragon, but same pattern as us

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19
Q

Zimmerman’s properties of sleep? (4)

Why do we need them?

A

In simpler nervous systems, we cannot use EEGs.

  1. Quiescence with species specific posture
  2. Increased arousal threshold
  3. Quick reversibility
  4. Homeostasis i.e. interruption leads to greater need
20
Q

Measuring sleep in flies?

A

Test tube - food and cotton at opposite ends with infrared sensor detecting crossing frequency.

21
Q

Overall conclusions about sleep across taxonomic ranks?

A

Very similar features - e.g. neurochemicals (exception of orexin, not in flies), patterns and overall properties
Certain features species-specific e.g. cycle length and side of brain

22
Q

Two mechanisms of biological rhythm control?

A

Passive/retroactive - relies on homeostasis adapting to changes
Proactively - biological timekeepers

23
Q

Examples of circadian rhythms? (7)

A 
Body temp
Hormone secretion
Locomotion
Sleep
Alertness/cognition
Muscle strength
Immune function
24
Q

What is voluntary activity?

A

Our main source of study for bio rhythms - behaviours that the animals would do anyway, e.g. hamsters running on a wheel

25
Q

What is an actogram?

A

Plot for rhythms - each successive day is a new row, and we can see the rhythm shifting:
- - - -
/ - - - -
// - - - -

26
Q

Entrainment?

A

Training the biological clock to sync with environmental cues - this gives an aligned actogram

27
Q

Circadian rhythms in insects?

A

Flies - crepuscular i.e. active at twilight and dawn

Crickets - start calling at dusk

28
Q

Key characteristics of circadian rhythms? (3)

A

Free-run in constant environments, around 24hrs
Synchronised by recurring changes in the environment
Anticipate these change i.e. occurs slightly before

29
Q

SCN?

A

Suprachiasmatic nucleus, in the hypothalamus, the master pacemaker in mammals
More active during the day

30
Q

Neurons of the SCN?

A

Also demonstrate individual clock activity - isolated ones give rhythmic output, synchronised in intact SCNs

31
Q

Genes involved in light/day cycle?

A

CLOCK and BMAL1 - stimulatory
PERIOD/CHRYPTOCHROME - inhibitory
(These are mammalian)

32
Q

Where does the SCN obtain info about time of day?

A

Retinohypothalamic tract (RHT) via the optic nerve

33
Q

Effector mechanism of the SCN?

A

SCN signals to pineal gland in absence of light, from which melatonin is secreted to induce sleep

34
Q

Examples of ultradian rhythms?

A

Human sleep cycles, growth hormone release

35
Q

Examples of infradian rhythms?

A

Bird migration, hibernation, reproductive cycles

36
Q

Circannual timer in sheep?

A

Short coat and small testes in summer, opposite in winter

37
Q

Role of prolactin in circannual timers? (sheep example)

A

Prolactin secretion in summer shrinks testes

Associated with melatonin, which detects day length changing to indicate season

38
Q

Neural control of prolactin?

A

Pituitary pars tuberalis - acts on secreting cells in association with melatonin to control levels seasonally

39
Q

Control of rhythms in marine environments? (2)

A

Gravitational force of the moon

Rotational force of the earth

40
Q

What is the tidal cycle?

A

2 high tides a day when moon is overhead = 12.4 hour cycle

One tide is the highest = 24.8 hour high tide cycle

41
Q

What is the bi-lunar cycle?

A

Moon and sun align giving spring tides, neap tides when they do not - 14 day cycle

42
Q

Circa-tidal rhythm in eurydice?

A

Lives in sand and emerges at high tide to swim and feed

Considers both the tidal cycles (24.8 hours) and which tide is the highest (increased swimming every 12.8 hours)

43
Q

Pigmentation cycle in eurydice?

A

More pigmentation deposited during light (to protect from UV) and less at night

44
Q

Sleep stage and eye movement?

A

REM

45
Q

Sleep stage and neck movement?

A

Waking/REM transitions

46
Q

Sleep stage and respiration/heart rate?

A

Highest when awake and REM

47
Q

Frequency of each sleep stage

A 
Awake - 15-30Hz
1-4-8Hz
2-10-15Hz
3-2-4Hz
4-0.5-2Hz
REM - 15-30 Hz

Animal Behaviour (16 decks)

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