96 - Sleep Physiology Flashcards

1
Q

What is sleep?

A

Behavioural state.
Decreased awareness of external stimuli.
Can rapidly return to wakefulness.

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2
Q
Why do we sleep?
1
2
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5
6
A
  • Learning
  • Brain development
  • Repair and maintenance
  • Clearance of metabolites
  • Energy preservation?
  • Avoid nocturnal hazards?
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3
Q

Number of Australians who might have a sleep disorder

A

~1.5 million

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4
Q

Signals used for polysomnography
1
2
3

A

EOG - electrooculography
EMG - Electromyography
EEG - Electroencephalography

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5
Q

Things that can also be measured in polysomnography

A

Video.
SpO2
Nasal airflow

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6
Q

Things that can also be measured in polysomnography

A

Video.
SpO2
Nasal airflow

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7
Q

Graphical representation of sleep

A

Hypnogram

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8
Q

Main features of wakefulness on a polysomnograph

A

Eye movements.
High levels of muscular activity
High frequency EEG

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9
Q

Main features of stage 1 and 2 non-REM sleep

A

No eye movements
Relatively high muscle activity
Lower frequency EEG

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10
Q

Main features of stage 1 and 2 non-REM sleep

A

No eye movements
Relatively high muscle activity
Lower frequency EEG

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11
Q

Main features of stage 3 non-REM sleep

A

No eye movements
Variable levels of muscle activity
Low frequency EEG (‘slow wave sleep’)

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12
Q

Main features of REM sleep

A

Rapid eye movements.
Low levels of muscle activity
Higher frequency of EEG

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13
Q

Main features of REM sleep

A

Rapid eye movements.
Low levels of muscle activity
Higher frequency of EEG

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14
Q

Effect of sleep on breathing
1
2
3 a b c d

A
• Lose wakefulness drive
• Behavioural influences
• Down-regulation of respiratory control mechanisms:
–upper airway muscles
–respiratory muscles
–respiratory reflexes
–chemosensitivity
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15
Q

Ventilation when asleep

A

Ventilation Falls At Sleep Onset And CO2 Rises Until A New Sleep Set-Point Is Reached

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16
Q
Cardiovascular changes during sleep
1
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3
4
A
  • Lower HR (particularly during NREM sleep)
  • Lower BP (at sleep onset)
  • Reduced cardiac output
  • Overall metabolic activity decreases markedly during sleep
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17
Q

What happens in an arousal during sleep?
1
2
3

A

Increased EEG, EMG frequency.
Increase ventilation, diaphragmatic activity.
Increase HR, BP

18
Q

What happens in an arousal during sleep?
1
2
3

A

Increased EEG, EMG frequency.
Increase ventilation, diaphragmatic activity.
Increase HR, BP

19
Q

What causes physiological responses to arousals during sleep?

A

Unclear.
Might be that systems suppressed when asleep are just starting up again.
Might be a waking reflex, to be able to respond to a dangerous stimulus waking you up from sleep.

20
Q

Number of arousals in severe obstructive sleep apnoea

A

Over 30/hour

21
Q

Dangers of severe OSA
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3

A

1) Increased risk of car accident
2) Higher risk of stroke
3) Higher risk of CVD

22
Q

Body part which regulates circadian rhythm

A

Suprachiasmatic nucleus

23
Q

Body part which regulates circadian rhythm

A

Suprachiasmatic nucleus

24
Q

Name for an external cue that can influence circadian rhythm

A

Zeitgeiber

25
Q

Example of a very strong zeitgeiber for sleep

A

Light

26
Q

Effect of light on circadian rhythm

A

Light inhibits the SCN
Lack of light increases melatonin levels (released from pineal gland)
Melatonin promotes sleep

27
Q

Effect of light on circadian rhythm
1
2
3

A

Light inhibits the SCN
Lack of light increases melatonin levels (released from pineal gland)
Melatonin promotes sleep

28
Q

*Two-process model of sleep

A

TWO PROCESS MODEL

29
Q

*Two-process model of sleep

A

TWO PROCESS MODEL
Circadian process tries to keep us awake.
Homeostatic process tries to get us to sleep

30
Q

*Two-process model of sleep

A

TWO PROCESS MODEL
Circadian process tries to keep us awake.
Homeostatic process tries to get us to sleep

31
Q

What physiological process might underlie the desire to sleep?

A

Metabolite/toxin clearance.

Sleeping mice had a greater clearance of beta-amyloid than mice who were awake or sedated.

32
Q

Danger of chronic sleep restriction

A

Performance in tasks becomes increasingly impaired, but subjective perception of performance normalises.
Therefore become less able to judge performance.

33
Q

Three functional systems which might control sleep

A

1) Arousal systems
2) Sleep promoting system
3) Orexin neurons

34
Q

Where are arousal systems located?

A

located in multiple areas within pons/midbrain

35
Q

Where is the sleep-promoting system located?

A

includes VLPO (ventrolateral pre-optic nucleus)

36
Q

Where are orexin neurons located?

A

located in the hypothalamus – project onto arousal systems (stimulate)

37
Q

Three functional systems which might control sleep

A

1) Arousal systems (maintains wakefulness)
2) Sleep promoting system (inhibits both orexin and arousal systems)
3) Orexin neurons (stabilise wakefulness)

38
Q

Where are arousal systems located?

A

Located in multiple areas within pons/midbrain

39
Q

Where is the sleep-promoting system located?

A

Includes VLPO (ventrolateral pre-optic nucleus)

40
Q

Where are orexin neurons located?

A

Located in the hypothalamus – project onto arousal systems (stimulate)

41
Q

Part of brain damaged in narcolepsy

A

Orexin neurons

42
Q

Part of brain damaged in narcolepsy

A

Orexin neurons