L1 - SLEEP Flashcards
1
Q
what is sleep
A
- a reversible behavioural state of perceptual disengagement from, and unresponsiveness to the environment
- reversible differs it from anaesthesia
- associated w/specific brain patterns/activities observed in EEG
- temporary loss of conciousness & decreased responsiveness to external stimuli; relaxed state
- muscle atonia in REM
- its an essential physiological process
1
Q
varying sleep times in mice
A
- different species sleep for different amounts of time
- engineered mice w/differing sleep time and structure but never one without sleep –> indicates that sleep serves a vital function
2
Q
Sleep in terrestrial animals
JM Siegel. 2005. Nature
A
- humans ~1/3 of lives asleep; other animals sleep even more, yet why we do remains a mystery
- sleep patterns vary widely; 18-20hrs in some species like bats/opposums; 3-4hrs giraffes/elephants
- sleep studies face challenges in quantification, often relying in visual observations and lacking systematic measurements
- correlations between sleep time, body mass & diet –> carnivores sleep most/ herbs least
- duration of sleep is correlated w/body mass and brain size, smaller animals have shorter sleep cycles –> not known why
3
Q
sleep in marine animals
JM Siegel. 2005. Nature
A
- unlike terrestrial animals, often exhibit unihemispheric sow waves during sleep
- one hemisphere = high-voltage EEG as it remains awake (eye open)
- no REM sleep –> maintain movement even during periods of SWA, challenging traditional definitions of sleep
4
Q
sleep stages (general)
A
- ~75% in NREM stages (N1, N2, N3); majority in N2 –> each stage = progressively deeper sleep
- 4-5 cycles per night; one complete cycle 90-110mins –> first REM period is short, as night progresses, longer REM and less time in NREM
5
Q
sleep stages- wake alert
A
- beta waves (12.5-30 Hz; highest F, lowest Amp) during eyes open phase –> desynchronised activity
- transition to alpha waves (8-12 Hz) when eyes close/ become more drowsy, slowly fade into N1
6
Q
sleep stages - N1
A
- 5% (1-5mins)
- light sleep
- theta waves (4-8 Hz)
- begins when more than 50% of a-waves become replaced with low amplitude, multiple frequency (LAMF) activity
- muscle tone present; regular breathing
7
Q
sleep stages - N2
A
- 45%
- heart rate & body temp drop
- sleep spindles = brief, powerful bursts of neuronal firing inducing Ca2+ influx into cortical pyramidal cells; mechanisms believed to be integral to synaptic plasticity & essential for memory consolidation
- K complexes = long delta waves (1s); maintain sleep & memory consolidation
- first cycle ~25 mins, lengthens w/each successive cycle
- where bruxism (teeth grinding) occurs
8
Q
sleep stages - N3
A
- deepest sleep (25%)
- delta waves (1-4Hz) = lowest F, highest Amp (slow-wave sleep, SWS)
- synchronised activity; neurons fire simultaneously
-most difficult to awaken from (>100 decibels); if awaken during N3, experience transient mental fogginess 0.5-1hrs after awakening - stage where body regenerates/ repairs tissues/ bones/ muscle, strengthens immune system
- when sleepwalking, terrors, bedwetting occurs
9
Q
sleep stages - REM
A
- 25%
- similar brain activity to wakefulness
- beta waves (12.5-30Hz) and desynchronized pattern
- associated w/dreaming
- not considered restful sleep
- muscle atonia (except eyes & diaphragm) & irregular breathing
- usually starts 90mins after sleep; each cycle increases (10mins - 1hr)
- tend to awaken spontaneously in the morning from REM
- increased O2 brain use; variable pulse & blood pressure; increased levels of Ach; brain is highly active (increase brain metabolism by 20%)
10
Q
what is an EEG
A
- non-invasive technique to measure brain waves/activity patterns associated w/different levels of conciousness
- records electrical activity in the brain
- place electrodes on scalp to detect & measure the electrical signals generated by neurons firing
11
Q
EEG invention
A
- Hans Berger
- cavalry man during WW1, fell off his horse
- before confirmation of his accident, sister dreamt about it
- Berger wanted to investigate telepathy: the possibility of transferring thoughts so aimed to use EEG to project thoughts & test if they could be detected by another person
- first person to observe & document regular electrical oscillations in human brain, which varied depending on levels of conciousness
- disproved telepathy
12
Q
Nathaniel Kleitman - “godfather of sleep”
A
- first human sleep labs in 1920s in U.chicago –> studying sleep & associated physiological processes in a controlled enviornment; analyse brain activity w/EEG during sleep
- found that sleep patterns can be affected by various factors: eg. mental illness, trauma –> changes in EEG in patients w/depression, schizo, PTSD
- was the groundwork for developing objective measures for evaluating sleep & sleep disorders
- prompted Aschoff & researchers in MUC sleep caves in 1960s/70s for circadian studies (total darkness/light)
- provided food at certain times of day to maintain some temporal organisation
- actogram over several days –> activity patterns follow a free-running rhythm w/each day’s activities starting slightly later than previous –> delayed onset of activity = endogenous circadian clock sits slightly longer than 24hrs
13
Q
how does the EEG work
A
- functionality = consistent across species primarily due to layered structure of the cerebal cortex (outermost layer responsible for higher functions)
- particularly important are pyramidal neurons
- neurons generate electrical signals when active –> fire action potentials
- active synapses allow the flow of ions (eg. K+) –> current flow between neurons
- the combined electrical activity of millions of neurons firing in synchrony creates detectable electrical signals picked up by electrodes in scalp (not individual neurons)
14
Q
EEG - wakeful state
A
- cortex is active –> processing sensory info, performing cognitive tasks, engaging in motor activities = irregular/ desynchronised activity
- reflects the dynamic and complex nature of cortical processing during wakefulness, w/ diff regions engaged in various tasks simultaneously
