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.
Define Sleep
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.
What are 6 properties of sleep
Properties of Sleep
- Specific postures
- Inactivity
- Reduced responsiveness
- Rapidly reversible
- Eyes Closed
- Beahvioural preludes
- “pre-sleep behaviour”
How is sleep measured?
- EEG: Summed brain-wave activity (Electroenchephalogram)
- EOG: Eye movement (Electroocuogram)
- EMG: Muscle Tone (Electromyogram)
What are the EEG activities of sleep
- 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)
Describe the EEG, EOG, EMG of 0.) Wakefulness
Wakefulness
EOG:
- High Amplitude
- Sharp waves represents eyeballs
EEG:
- Mixture of Alpha (dominant) and Beta Waves
- “Relaxed Wakefulness”
EMG:
- Muscle activity present
Describe the EEG, EOG, EMG of 1.) Non-Rem Sleep
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
Describe the EOG and EEG of 2.) Non-Rem Sleep
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
Describe the EOG and EEG of 3.) Non-Rem Sleep
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
Describe the EEG and EMG of 4.) Non-Rem Sleep
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
Summary of Non-REM Sleep
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
What is the respiration, heart rate, muscle activity, cognitive activity of non-REM sleep?
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.
Describe the EEG, EOG, EMG of REM Sleep
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)
What is the respiration and heart rate during REM? And what are properties of dreams
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
What are Pontine-Geniculate-Occipital (PGO) waves?
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
What is the sexual status during REM sleep
Signs of sexual arousal
- can use REM sleep as an impotence test
Summarize Non-REM and REM Sleep Stages (% Asleep)
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%
Summarize Non-REM and REM Sleep Stages +Relaxed ((EEG Wave Type, Frequency, Amp)
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)
What is the structure of sleep through the night?
- 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
What is the ontogenetic development of sleep
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
Theory behind the control of sleep
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
Elaborate on Homeostatistic Control of Sleep (Process S)
- 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
Elaborate on Circadian Control of Sleep (Process C). Give an Example
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.
Describe the constant environment experiment
- No time cues
- Day 1-20: Lights
- Day 21: Participants control light
- Participants go to bed later and wake up later
weIntepretations of the constant environment experiment
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).
