Overview and Sleep Flashcards
1
Q
Circadian Rhythms
A
- Rhythms associated w/ a 24-h day (alternating periods of light + darkness) = humans have adapted to living in an env that has a light + dark rhythm
- The term circadian literally means 24 hrs
- Generated by the body clock
○ Most clocks run slightly longer than 24h (can be up to 25h)
○ Some slightly shorter (e.g. 23h)
○ How is the body clock reset (later) = we need to reset our clock everyday - In part genetically determined = is why sleep rhythm is different b/w people = some people genetically wired to go to bed early + wake up early + vice versa
- Examples of circadian rhythms:
○ Core body temp
○ Blood pressure, heart rate
○ Sleep-wake rhythm: chronotype - A caveat: for teenagers they have a tendency to go to bed late = not of their own doing it’s because there brain actually determines that - called the delayed sleep phase disorder
- EATING too much before bed can have severe consequences
- Circadin = good pill for people with insomnia
2
Q
The circadian time-keeping system
3 clocks
A
- Sun clock: the sun gives light + light + darkness can regulate the SCN - light that enters the retina at the back of the eye - this signal is transmitted to the SCN - the SCN will suppress the release of melatonin (readings of darkness)
○ Melatonin (hormone of darkness): Only released at night - induces + maintains sleep, light suppresses melatonin so that during the daytime you are fully alert - except can become sleepy if sleep deprived, computer screen light can suppress melatonin - Body clock: every single cell in your body has a clock (have 10 trillion cells), however there is only one master clock (SCN) residing in the brain in this nucleus called the suprachiasmatic nucleus (SCN). Other clocks are peripheral or cellular clock.
○ The SCN synchronises all the peripheral clocks
○ PA in your muscles can have some feedback to your master clock - Social clock: refers to social activities e.g. going to bed at 4am - melatonin supressed as exposed to light, can cause problem for the master clock, causes physiological systems/circadian rhythms to be altered = means the master clock has difficulty to synchronise all the clocks e.g. shift work, jetlag
- If all clocks are synchronised = get optimum health/sleep
3
Q
Sleeping Behaviour
A
- An orchestrated, programmed event:
○ Lights out –> melatonin
○ Lying down w/ eyes closed –> melatonin
○ ‘lights out’ of thought processes
§ Want to promote the release of melatonin = only comes when dark
4
Q
What is sleep?
A
- Changed consciousness / partial unconsciousness; can be aroused by stimulation
○ If unconscious = in a coma, not in a coma when we sleep - Cortical activity depressed - somewhat
- Control of respiration, HR, + blood pressure continues
- Environmental monitoring continues to some extent
- Very hard to wake a person up during deep sleep
- If cold skin receptors can sense temp - pull a blanket on
5
Q
Human Sleep
A
- Polysomnography (PSG) - measures physiological signals
○ Electroencephalogram (EEG) - measures brain activity
○ Electrooculogram (EOG) - measures eye movts
○ Electrocardiogram (ECG) - measures heart rhythm/rate
○ Chin + leg electromyogram (EMG) - chin = snoring + any arousal from sleep
6
Q
NREM + REM
A
- NREM Sleep (non-rapid eye movt sleep)
- Sleep states
○ NREM sleep 1 + 2 - light (S1, S2 or N1, N2)
○ NREM sleep 3 (S3 or N3) or slow wave sleep, SWS = deep sleep - REM sleep (rapid eye movt sleep)
- The NREM-REM cycle: 90-120min (adult)
○ 4-6 cycles per night - The NREM-REM cycle: 50min (infant)
○ 8-12 cycles or more
7
Q
% OF THE NIGHT in each stage
A
- Light stages for only 5% i.e. when falling asleep = can also see N1 throughout the night if you slept poorly or are a poor sleeper
- Half of the night (50%) of sleep throughout the night consists of light sleep N2
- Deep sleep represents only 20% of total night sleep
- REM sleep 25%
8
Q
Nonrapid eye movement (NREM) sleep
A
- Light sleep: - periodic breathing in 0.5% of population
- Cheyne stokes breathing = period of apnoea (no breathing) = O2 levels drop in blood, CO2 builds up
- SWS:
○ “worth more” in the physical restorative process
§ memory consolidation (in both REM + NONREM sleep)
§ toxic waste removal (β-amyloid proteins – Alzheimer’s)
○ marked stability of ventilatory pattern
○ when most nightmares, night terrors + sleep walking occur
9
Q
Rapid eye movement (REM) sleep
A
- Paradoxical sleep = brain activity almost looks like the same in awake state
○ EEG pattern more typical of the awake state
○ Phasic + tonic REM = can see phasic eye movts
○ Loss of muscle tone = diaphragm only skeletal muscle that works during sleep
○ Low amplitude submental muscle activity
○ Muscular twitches - Most dreaming occurs - lucid dreams
- You do also dream in non-rem sleep
○ Memory traces of dreams will disappear very quickly if you don’t try + remember your dream straight away - Erection of penis (4-6 times - adults, older adults probably a lot less) + clitoris = occurs in REM sleep
- Body temp, HR, BP + respiratory rate increases to near waking level, but decreases gastrointestinal motility = important to rest your body
- Respiratory irregularity
○ Apnoea’s common during phasic REM sleep:
§ Healthy infants: 2-10s
§ Healthy children + adults: 10-20s - Provides a subtler form of restoration for psychological wellbeing
- Memory consolidation
10
Q
The hypnogram
A
- SWS - a marker of sleep homeostasis
- In the first sleep cycle = get a large chunk of deep sleep = up to around 90-100mins worth = allows you to become vigilant the next morning
- Should get around 90-110 mins of slow wave sleep = biggest chunk usually occurs in the first sleep cycle
- Polarity - circadian timing of REM sleep = largest occurs at the end of the night before waking = why you can remember some dreams
11
Q
Metrics of sleep quality (objective)
A
Objective measures (polysomnography - more complex, actigraphy - more for research)
* sleep initiation (sleep onset latency (SOL) - how long does it take you to fall asleep), sleep maintenance (wake after sleep onset, WASO - how much you wake up during the night), sleep quantity (total sleep time, TST)
sleep architecture (N1, N2, N3 (SWS), REM sleep)
12
Q
Metrics of sleep quality (subjective)
A
Subjective measures (sleep diary, self-report)
* one’s satisfaction of the sleep experience
* refreshment upon awakening
* sleepiness, sleep disturbance, sleep duration, sleep efficiency (SE), sleep latency, sleep medication use
○ SE = % time spent asleep while in bed
13
Q
Concept of sleep misperception [1]
A
- A mismatch b/w subjectively perceived + objectively recorded sleep times
- Occurs in patients w/ insomnia + good sleepers(!) Why?
- How tight is this relationship?
= A robust correlation b/w subjective + objective sleep times
14
Q
Concept of sleep misperception [4]
Findings
A
- the subjective perception of sleep time remains well in proportion w/ respect to objective sleep time
- Why? Different brain activity level during sleep!
○ Under estimators displayed higher electroencephalographic (EEG) activation in both REM + NREM sleep –> ↑ activity of arousal-related system = if brain activity is higher would perceive to think they had less sleep
○ Over estimators showed lower EEG activation in REM sleep –> ↓ activity of arousal-related system = EEG arousal/cortical activity is lower = perceive that they slept well - as brain activity is lower
15
Q
Sleep architecture in normal ageing
A
- Total sleep time stays the same or ↓ w/ age
- Total nightly amount of individual sleep stages alter w/ age
- %REM sleep: infancy >childhood >adulthood> old age =
- Slow wave sleep: - decreases w/ age - the amplitude of delta waves declines in old age
- In infancy spend about 80% of sleep in REM sleep = synapses being formed
- As we age amount of REM sleep decreases up to about 1st year of age - then it stabilises at around 20%
- Stage 2 sleep = a lot more in infancy then stabilises to about 50%
- What changes w/ ageing is the reduction in SWS - amplitude is ‘squashed’ w/ age + also duration of SWS (delta) is reduced = due to all of our systems ageing including our body clock
