L13 - Sleep

Question 1

Behaviourally, what is sleep?

Answer 1

A normal absence of consciousness

Question 2

Electrophysiologically, what is sleep?

Answer 2

A pattern of specific brain wave activity

Question 3

What shows that sleep is a basic homeostatic need?

Answer 3

• Requirement for sleep increases with time awake
• Sleep/sleep-like behaviour occurs in all multicell organisms

Question 4

In humans, what does sleep duration change with?

Answer 4

Age

Question 5

What is the relationship between organism size and length of sleeping period?

Answer 5

Smaller organisms alternate short periods of sleeping/waking whereas bigger organisms have less longer periods of sleep

Question 6

What ecological factors suppress sleep?

Answer 6

Protection against predators, enhanced mating success, incompatibility with swimming, thermoregulation, need to forage for food, adaptive inactivity

Question 7

What intrinsic factors promote sleep?

Answer 7

Enhancement of memory consolidation, rewiring of CNS, energy conservation, metabolic clearance, sensorimotor tuning, synaptic homeostasis

Question 8

As someone becomes “more unconscious” what happens to the amplitude and frequency of their EEG waveforms?

Answer 8

Amplitude increases and frequency decreases as person becomes “more unconscious”

Question 9

What is alpha activity associated with?

Answer 9

Awake but with eyes closed

Question 10

What is beta activity associated with?

Answer 10

Being alert, attentive & actively thinking.

Question 11

What is theta activity associated with?

Answer 11

Stage 1 sleep

Question 12

What are sleep stages 2-4 called?

Answer 12

slow wave sleep (SWS) or
non-rapid eye movement (NREM) sleep

Question 13

What is REM sleep also known as?

Answer 13

paradoxical sleep

Question 14

What is delta activity associated with?

Answer 14

Stage 3 and 4 sleep

Question 15

How many sleep cycles are in average night?

Answer 15

5

Question 16

What happens to length of REM and SWS throughout each sleep cycle?

Answer 16

Length of REM increases, length of SWS decreases

Question 17

Which cycles is deep sleep present in?

Answer 17

Only first 2 cycles

Question 18

What determines sleep patterns?

Answer 18

Interaction between homeostatic
sleep pressure and an internal (circadian) clock

Question 19

What could explain smaller animals sleep patterns?

Answer 19

The homeostatic sleep pressure being stronger and the circadian clock being weaker

Question 20

What are the three neural systems actively involved in controlling sleep?

Answer 20

Forebrain system (SWS sleep)
Brainstem system (activates forebrain system into waking)
Brainstem system (triggers REM sleep)

Question 21

What have nerve transection studies by Frédéric Bremer shown?

Answer 21

When nerves were cut below the brainstem all stages of sleep were maintained
When the brainstem was cut off the rat was in a constant state of SWS

Question 22

What brain structures are in the ascending arousal system?

Answer 22

Dorsal Raphe, Lateral Dorsal Tegmentum, Pedunculopontine Tegmentum, Locus Coeruleus, Basal Forebrain, Lateral Hypothalamus, Tuberomammillary nucleus

Question 23

What does the dorsal raphe release?

Answer 23

Serotonin

Question 24

What does the Locus Coeruleus release?

Answer 24

Noradrenaline

Question 25

What does the Lateral Hypothalamus release?

Answer 25

Orexin

Question 26

What does the Tuberomammillary nucleus release?

Answer 26

Histamine

Question 27

What is orexin also known as?

Answer 27

Hypocretin

Question 28

Where does orexin project to?

Answer 28

• projects all over the brain
• Signal through the Ox1R and Ox2R receptors in target regions

Question 29

What do orexin KO (knockout) mice show?

Answer 29

Reduced wakefulness and increased SWS/ REM

Question 30

What does orexin promote?

Answer 30

Wakefulness

Question 31

What are the 4 main symptoms of narcolepsy?

Answer 31

• Excessive daytime sleepiness with irresistible sleep attacks during the day
• Cataplexy (brief episodes of muscle weakness/paralysis precipitated by strong emotions such as laughter or surprise).
• Sleep paralysis
• Hypnagogic hallucinations or dream-like images that occur at sleep onset

Question 32

What did post-mortem brains from humans with narcolepsy show?

Answer 32

Reduced number of orexin neurons

Question 33

What is unihemispheric sleep?

Answer 33

When only one hemisphere of the brain/ one eye sleeps at one time

Question 34

What is relationship between unihemispheric sleep and risk of predation?

Answer 34

More likely to perform unihemispheric sleep if risk of predation is high

Question 35

How do great frigate birds sleep when flying for 10 days at a time?

Answer 35

They unihemispherically sleep on the ascension of their flight
They sleep a much lower percentage of the time compared to when they aren’t flying

Question 36

How do great frigate birds fly long distances?

Answer 36

• Primarily rely on a soaring–gliding strategy
• Circular rising on thermals (air currents)- soaring followed by straight gliding down

Question 37

Which hemisphere is asleep for great frigate birds when ascending while circling right?

Answer 37

Their left hemisphere, always opposite to direction of circling

Question 38

In reptiles, what did video analysis of closed eyes paired with EEG recordings reveal about sleep patterns?

Answer 38

• Regularly occurring episodes of REM
• sleep cycles take ~80s in this species (P. vitticeps)

Question 39

What 4 factors are used to define sleep when EEG cannot be used?

Answer 39

• A period of quiescence associated with a species specific posture
• An increased arousal threshold (reduced responsiveness to external stimuli)
• Quick reversibility to wakefulness
• Homeostasis

Question 40

Evidence for flies sleeping:

Answer 40

• Flies in this ‘Resting’ Posture Show Elevated Arousal Thresholds
• Deprivation results in rebound ‘Rest’

Question 41

What occurs in honey bees when sleep deprived?

Answer 41

• learning and memory impaired
• Waggle-dance precision reduced
• navigational memory is impaired