W5L1 - Introduction to Sleep Flashcards

1.) Discuss what sleep is and how it can be measured. 2.) Identify different sleep stages. 3.) Describe the control of sleep broadly.

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1
Q

Define Sleep

A

Sleep

  • Condition of body and mind
  • which typically recurs for several hours per day
  • in which the eyes are closed, postural muscles relaxed, and consciousness is practically suspended.
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2
Q

What are 6 properties of sleep

A

Properties of Sleep

  • Specific postures
  • Inactivity
  • Reduced responsiveness
  • Rapidly reversible
  • Eyes Closed
  • Beahvioural preludes
    • “pre-sleep behaviour”
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3
Q

How is sleep measured?

A
  1. EEG: Summed brain-wave activity (Electroenchephalogram)
  2. EOG: Eye movement (Electroocuogram)
  3. EMG: Muscle Tone (Electromyogram)
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4
Q

What are the EEG activities of sleep

A
  • Active Eyes Open Wakefulness
    • Beta Activity (13-30Hz)
    • Desynchrony: Low amplitutde, High Frequency
  • Eyes Closed Wakefulness
    • Alpha Activity (8-12Hz)

With sleep, EEG synchrony develops (High Amplitude, Low Hz)

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5
Q

Describe the EEG, EOG, EMG of 0.) Wakefulness

A

Wakefulness

EOG:

  • High Amplitude
  • Sharp waves represents eyeballs

EEG:

  • Mixture of Alpha (dominant) and Beta Waves
    • “Relaxed Wakefulness”

EMG:

  • Muscle activity present
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6
Q

Describe the EEG, EOG, EMG of 1.) Non-Rem Sleep

A

Stage 1: Non-REM

EOG:

  • Slow eye-rolling
    • Dozing off

EEG:

  • Theta Activity (4-7Hz), characteristic of Stage 1
  • Little K Complex
    • EEG from negative (up) to positive (down) to baseline quickly
    • Amplitutde >50mV and greater than 0.5ss

EMG:

  • Muscle activity reduced
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7
Q

Describe the EOG and EEG of 2.) Non-Rem Sleep

A

Stage 2: Non-REM

EOG

  • Activity picked up likely from EEG

EEG:

  • Large K Complex
    • Amplitutde >50mV and greater than 0.5s
  • Sleep Spindle (Characteristic)
    • Period of high activity greater than alpha activity.
    • Between 11-16 Hz and lasts about a second
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8
Q

Describe the EOG and EEG of 3.) Non-Rem Sleep

A

Stage 3: Non-REM

EOG

  • Activity picked up likely from EEG

EEG:

  • Delta Waves
    • K complexes occurring together (Waves large ampltitude, slow speed)
    • >75mV and 0.5-2s
    • Once more than 20% of the epochs (6s) contains delta waves, considered Stage 3
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9
Q

Describe the EEG and EMG of 4.) Non-Rem Sleep

A

Stage 4: Non-REM

EEG:

  • Delta Waves
    • K complexes occurring together (Waves large ampltitude, slow speed)
    • >75mV and 0.5-2s
    • Once more than 50% of the epochs (6s) contains delta waves, considered Stage 4 (Deep)

EMG

  • Muscle tone drops substantially
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10
Q

Summary of Non-REM Sleep

A

Stage 1: N1

  • Theta Activity
    • 4-7Hz
    • Low in amplitude.

Stage 2: N2

  • K Complexes and Sleep Spindles
  • When K-Complexes get larger and start to merge, delta waves (slow, large amplitude waves)

Stage 3: N3/SWS

  • Delta waves >20% of epoch

Stage 4: N3/SWS

  • Delta waves >50% of epoch
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11
Q

What is the respiration, heart rate, muscle activity, cognitive activity of non-REM sleep?

A

Respiration and HR

  • Stable and Regular Respiration (slightly lower than waking respiration)
  • Regular heart rate and blood pressure (typically slightly lower than wake but don’t vary too much).

Muscle Tone:

  • Present (lower than wake)

Cognitive Activity

  • Cognitive activity
    • Rational and Thought-Like
    • If woken, would respond rationally (e.g. they’ll say they were thinking about what they were doing during the day). This is different from REM sleep.

Difficult to rouse from slow wave sleep.

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12
Q

Describe the EEG, EOG, EMG of REM Sleep

A

REM Sleep

EEG:

  • Theta Activity
    • Desyncrhonized EEG Pattern
    • Similar to Stage 1 non-REM
  • “Sawtooth Waves”
    • Negative deflections followed by positive deflections, in runs
    • Necessary but insufficient for REM
      • Eye Movement
      • Low muscle activity
      • Theta-Pattern

EOG:

  • Rapid Eye Movement
    • Distinguishing from Non-REM

EMG

  • Loss of muscle tone/paralysis (except respiration and eye muscle)
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13
Q

What is the respiration and heart rate during REM? And what are properties of dreams

A

REM

  • Respiration, heart rate and blood pressure is much more variable during REM sleep and these parameters matches dream content
    • Dreams are vivid and emotional
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14
Q

What are Pontine-Geniculate-Occipital (PGO) waves?

A

In animals, PGO waves occur during REM sleep.

  • Originate in pons, propagate to the lateral geniculate nucleus and through to the occipital cortex
  • Can’t test in healthy humans, but we clinical patients show these waves
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15
Q

What is the sexual status during REM sleep

A

Signs of sexual arousal

  • can use REM sleep as an impotence test
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16
Q

Summarize Non-REM and REM Sleep Stages (% Asleep)

A

Non-Rem Stage 1: N1

  • 5%

Non-Rem Stage 2: N2

  • 45%

Non-Rem Stage 3: N3/SWS

  • 12%

Non-Rem Stage 4: N3/SWS

  • 13%

REM:

  • 25%
17
Q

Summarize Non-REM and REM Sleep Stages +Relaxed ((EEG Wave Type, Frequency, Amp)

A

Awake

  • Beta (>12Hz)

Relaxed

  • Alpha (8-12Hz)

Non-Rem Stage 1: N1

  • Theta (4-8Hz)

Non-Rem Stage 2: N2

  • Theta (4-8Hz), K-Complex. Sleep Spindles

Non-Rem Stage 3: N3/SWS

  • Delta (>= 75mV, 0.5-2Hz), Theta

Non-Rem Stage 4: N3/SWS

  • Delta (>= 75mV, 0.5-2Hz), Theta

REM:

  • Theta (4-8Hz)
18
Q

What is the structure of sleep through the night?

A
  • Stages at 90 minutes
  • Stage 1 (Transition) > Stage 2 > Stage 3+4 (Deep Sleep) > Short bout of REM > Repeat
    • First few cycles, predominance of deep sleep
    • End of night, predominance of REM sleep.
      • REM sleep occurs most typically in the morning. In your last sleep cycle, you spend about an hour of that cycle in REM sleep
19
Q

What is the ontogenetic development of sleep

A

Age 0/Birth

  • 16 hours of the day asleep
  • 50% of sleep is REM

Age 2

  • % of REM sleep decreases dramatically
  • 25% of sleep is REM.

Age 2 - Adoloscene

  • Decline of Sleep (NREM/REM)
  • 20-25% of sleep is REM

TLDR: Proportion of REM and amount of sleep declines over life

20
Q

Theory behind the control of sleep

A

Borbley 2 Factor Model

  • Homeostatic factor (Process S)
    • Increase exponentially during wakefulness (sleep drive increases)
    • Decrease exponentially during sleep (sleep drive decreases)
  • Circadian factor (Process C)
    • Sine-Wave
    • Internal Biological Clock

Magnitude of the difference between the functions defines the propensity to sleep

21
Q

Elaborate on Homeostatistic Control of Sleep (Process S)

A
  • Regulatory process are activated to ensure that appropriate levels of sleep occur, including rebound effects
    • Sleep is reduced, negative consequences ensue
  • Homeostatic process in sleep is reflected in SWS
    • Amount of slow wave sleep diminishes as the sleep cycles go on.
    • Sleep-deprivated indiviudal has double (substnatially elevated) SWS
22
Q

Elaborate on Circadian Control of Sleep (Process C). Give an Example

A

Circadian rhythms

  • One cycle: 24 hours
    • Light is an external cue that can set the circadian rhythm
    • Endogenous
      • Internally generated, biological clock
      • Consistent with day time hours, the plant would open up its leaves, despite not getting any light and during the night it would roll it leaves up.
23
Q

Describe the constant environment experiment

A
  • No time cues
  • Day 1-20: Lights
  • Day 21: Participants control light
    • Participants go to bed later and wake up later
24
Q

weIntepretations of the constant environment experiment

A

Constant Environment Experiment

  • Sleep-wake cycle remains rhythmical despite the external time and light cues removed
    • Rhythmicity must be internal
  • Period of the internal clock must be greater than 24 hours
    • 24-hour period must be from external factors
    • (Internal clock is aligned to 24-hour time as a result of external factors such as clocks and lights).