Sleep Flashcards
1
Q
How is sleep research conducted?
A
- in a sleep laboratory
- EEG
- EMG
- EOG
2
Q
What is an electroencephalogram?
A
- EEG
- measure brain activity by attaching electrodes to the scalp to record
3
Q
What is an electromyogram?
A
- EMG
- measure muscle activity by attaching electrodes to the chin to record
4
Q
What is an electro-oculogram?
A
- EOG
- electrodes are places near the eyes to measure eye movements
5
Q
What are the types of EEG signals during sleep?
A
- beta activity
- alpha activity
- theta activity
- delta activity
6
Q
What is beta activity?
A
- 13-30 Hz
- typical of an aroused state
- reflects desynchronous neural activity (high frequency, low amplitude oscillations)
7
Q
What is alpha activity?
A
- 8-13 Hz
- typical of awake person in a state of relaxation
8
Q
What is theta activity?
A
- 4-8 Hz
- appears intermittently when people are drowsy
- prominent during early stages of sleep
9
Q
What is delta activity?
A
- < 4 Hz
- occurs during deepest stages of slow-wave sleep
- reflects synchronized low frequency, large amplitude brain activity
10
Q
What is rapid eye movement sleep?
A
- REM sleep
- associated with desynchronized EEG activity (beta)
- rapid eye movements
- dreaming
- muscle paralysis: muscles are totally inactive apart from occasional twitches
- cerebral blood flow and oxygen consumption increase
11
Q
What is slow-wave sleep?
A
- stage 3/4 non-REM sleep (deep sleep)
- corresponds to large amplitude, low frequency oscillations of brain activity
- this pattern of neural activity reflects synchronized bursts of action potentials in large collections of neurons
12
Q
What are the REM deprivation studies?
A
- animals can sleep sitting or standing up, but muscles go limp during REM sleep
- animals fall off the pedestal and into the water, waking them up
- only getting little non-REM sleep
- floor moves when sleep
13
Q
What happens to the animal in the REM deprivation studies?
A
- 2-3 weeks of sleep deprivation: lose control of their metabolic processes and body temperature
- soon they lose wright and die
14
Q
What does lack of sleep cause?
A
- death
- sleep is critical for survival
15
Q
What happens if you don’t sleep?
A
- feel tired
- mind deteriorates, body is physically fine
- delayed reaction times
- poor judgment
- increases in stress hormones, mood swings, and impulsive behavior
- worse learning and memory
- increase propensity for weight gain, migraines, hallucinations, dementia, seizures, and death
- sleep debt must be repaid
- microsleep states
- sleep disruptions often precede and exacerbate mental illnesses
16
Q
What are microsleep states?
A
- fall asleep for brief episode lasting several seconds
- perceptually blind
- unaware they have fallen asleep
- brain shut off
17
Q
How do dolphins sleep?
A
- sleep alternates between the two cerebral hemispheres
- can’t entirely go to sleep
- maintaining vigilance during sleep
18
Q
How often do newborn humans sleep?
A
- 16 hours a day
- 50% REM
- 50% NREM
19
Q
How often do adult humans sleep?
A
- 7 hours day
- 25% REM
- 75% NREM
20
Q
What differences are there between species?
A
- amount of sleep
- ratio of REM to NREM sleep
- length of sleep cycles
21
Q
What is the measure of a sleep cycle?
A
- average time between two REM events
22
Q
How do predatory animals sleep?
A
- indulge in long, uninterrupted periods of sleep
23
Q
How do preyed upon animals sleep?
A
- sleep during short intervals that may last no more than a few minutes
24
Q
How is sleep and body weight correlated?
A
- the amount of time a species sleeps each day is inversely correlated with weight
- less hours of sleep = heavier
25
Q
How is metabolic rate and body weight correlated?
A
- overall metabolic rate increases as mass increases
- metabolic rate per pound (or per cell) decreases as mass increases
26
Q
What are the correlation of body mass, brain mass, metabolic rate, heart rate, life span, sleep time and length of sleep cycles?
A
- high body mass
- high brain mass
- high overall metabolic rate
- low metabolic rate per kg/cell
- low heart rate
- high life span
- low total sleep time
- high length of sleep cycles
27
Q
What is an example of the correlations for large animals?
A
- low metabolic rates per cell
- long lifespans
- don’t sleep much
- each sleep session is long
28
Q
Why do all these correlations exist?
A
- economies of scale related to heat savings and nutrient/waste distribution networks
- large animals benefit from economies of scale, so each cell doesn’t have to work as hard as it does in a small animal
- sleep time is highly correlated with all of these variables suggests that sleep may be critical for a restorative process
29
Q
What are the main theories about why animals sleep?
A
- to recover from physical or mental exertion
- brain processing
- waste removal
30
Q
What is the theory that animals sleep to recover from physical or mental exertion?
A
- the amount of time spent exercising and thinking should correlate with total sleep time
- amount of sleep people get does not correlate very well with how much or how little they exercise or study
- reduction in blood pressure and heart rate when people sleep, but the caloric difference between a person sleeping and sitting still across 8 hours is negligible
31
Q
What is the theory that animals sleep for brain processing?
A
- how can the brain update synaptic weights while it is currently operational and constantly receiving new information? (it can’t)
- sleep gives the brain an opportunity to reorganize data and archive memories (cannot be done efficiently while awake)
- synaptic modifications clearly occur during sleep
- learning and memory are impacted by sleep
- amount of slow-wave and REM sleep people get correlates with improvements in declarative and procedural memory
- during sleep, brain actively processing information and transferring it between different areas (within and between cells)
32
Q
What is the short explanation of the brain processing theory?
A
- sleep housekeeping function to maintain network stability
- learn during day
- need to reorganize things offline
33
Q
What is the theory that animals sleep for waste removal?
A
- total sleep time correlates with body size (as well as brain size, metabolic rate, heart rate, and life span)
- maybe it is critical for a process that benefits from economies of scale: nutrient use or waste removal
- some evidence suggests sleep is required for the efficient removal of waste products from the brain
- concentration of many proteins in the brain increases across periods of wakefulness and decreases across periods of sleep
- the clearance of proteins and waste products from the brain is almost nonexistent during wakefulness but really high during sleep
34
Q
How does the waste removal in the brain work?
A
- during sleep, glial cells in the brain (astrocytes) seem to lose water and shrink in size
- increases volume of interstitial space
- promotes diffusion of cerebrospinal fluid through the brain, clearing away waste
- big animals may sleep less than small animals because waste clearance systems in the brain benefit from economies of scale
- larger brains have more space to accumulate garbage, and can clear away waste faster than smaller brains
35
Q
What is the glymphatic system?
A
- CSF circulates around the brain and diffuses into it, into the interstitial space, becoming the extracellular solution that surrounds neurons
- as CSF moves through the interstitial space, it clears waste products away before exiting into blood vessels
- system removes excess proteins and other waste from the interstitial space of the brain
- clearance of waste minimal during waking but high during sleep
36
Q
Why didn’t animals just evolve bigger brains so CSF can diffuse around the brain and clear away waste all the time?
A
- no one knows
- almost all signaling molecules in the brain act via diffusion
- constraining diffusion is a prominent aspect of regulatory control
- evolutionary pressure to control and constrain diffusion within the brain to such an extent that waste products can now not be effectively cleared while the brain is functioning
- sleep may have evolved to let the brain perform optimally most of the day
37
Q
What is a circadian rhythm?
A
- changes in behaviour and physiology that follow a 24-hour cycle
- controlled by internal biological clocks
- run in the absence of light
- daily variation in light levels keep the clock adjusted to 24 hours
38
Q
What happens if we shift the light cycle of rats?
A
- quickly adapt to change
39
Q
What happens to rats if the light is constantly dim?
A
- maintain their circadian rhythms
- rhythms drift slightly over time
- a brief pulse of bright light can shift their internal clock
40
Q
What is the suprachiasmatic nucleus (SCN)?
A
- of the hypothalamus
- regulates circadian rhythms
- receives a direct input from the retina (knows how much light)
41
Q
What happens if the SCN is lesioned?
A
- dramatically alters circadian rhythms
- alter the length and timing of sleep-wake cycles
- do not change the total amount of time that animals spend asleep
- sleep and wake up at random times
42
Q
What is a biological clock?
A
- rhythms of sleep and temperature cycles
- sleep from 10 pm to 7 am
- every cell in SCN keeps its own clock, coordinating to create master clock
43
Q
What makes the clock of SCN neurons “tick”?
A
- circadian rhythms are maintained by the production of several genes and two interlocking feedback loops
- when expression of one proteins gets high enough, it inhibits its own production and promotes the expression of a different protein
44
Q
What is advanced sleep phase syndrome?
A
- mutation of a gene, per2, causes a 4-hour advance in the biological clock
- strong desire to fall asleep at 7pm and wake up at 4am
45
Q
What is delayed sleep phase syndrome?
A
- mutation of a gene, per3, causes a 4-hour delay in the biological clock
- desire to fall asleep at 2am and wake up at 11am
46
Q
What is the sleep molecule hypothesis?
A
- what determines how much an animal needs to sleep
- consistent with the waste removal theory
- build-up of many molecules in the interstitial fluid of the brain during waking hours, cleared away during sleep
- some promote drowsiness and sleep at high concentrations
- adenosine molecule
47
Q
What is the adenosine molecule?
A
- adenosine receptors on neurons throughout brain + extracellular adenosine builds up during waking hours
- levels rise in the brain during waking hours
- accumulate even more with sleep deprivation
- levels fall rapidly in brain during sleep
- drowsiness, and during and depth of sleep strongly modulated by adenosine receptor signaling
- one of many sleep-inducing molecules in the brain
- build-up of these molecules during waking hours that underlies animals’ homeostatic need for sleep
48
Q
What is an example of an adenosine receptor antagonist?
A
- caffeine
49
Q
What are the wake promoting signaling molecules?
A
- serotonin
- norepinephrine
- acetylcholine
- orexin
- histamine
are released by neurons that show increased activity during periods of arousal, alertness, and wakefulness and decreased activity during slow-wave sleep
50
Q
What is orexin and histamine?
A
- neuropeptides
- released by neurons in the hypothalamus
51
Q
What do histamine receptor blockers do?
A
- antihistamines
- often cause drowsiness
52
Q
What does norepinephrine neuron activity mean?
A
- positively correlate with focus and attention
53
Q
What does serotonin (5-HT) neuron activity mean?
A
- positively correlates with cortical arousal
- drugs that increase serotonin signaling tend to suppress aspects of REM sleep (without affecting memory)
54
Q
What is the ventral lateral preoptic area (vlPOA)?
A
- of the hypothalamus
- promote sleep
- electrical stimulation causes drowsiness, sometimes immediate sleep
- vlPOA neurons inhibit wake-promoting neurons
- area receives inhibitory inputs from the same regions it inhibits
- reciprocal inhibition; flip-flop circuit
55
Q
What happens if the vlPOA is lesioned?
A
- suppress sleep and cause insomnia
56
Q
What do vlPOA neurons do?
A
- inhibit wake-promoting neurons
57
Q
What is the sleep/wake flip-flop circuit?
A
- sleep-promoting region in vlPOA —- brain stem and forebrain arousal system
- both regions cannot be active at the same time
- switch from one state to another is fast
- when one is activated the other is inhibited
58
Q
When is the animal awake (according to flip-flop circuit)?
A
- when arousal, wake promoting system is more active than the vlPOA neurons
59
Q
When is the animal asleep (according to flip-flop circuit)?
A
- when the vlPOA neurons are more active than the wake promoting arousal system
60
Q
What does adenosine signaling do?
A
- activate sleep-promoting vlPOA neurons
- inhibit arousal-promoting acetylcholine (ACh) neurons
- influence of adenosine signalling during the day can be masked by other regulators of sleep and arousal (SCN neuron activity)
- when the clock of SCN neurons aligns with the build-up (or clearance) of sleep-promoting molecules, the network flip-flops and animal transitions into (or out of) sleep
61
Q
What is orexin?
A
- peptide produced by neurons in the lateral hypothalamus
- orexin neuron activity promotes wakefulness
- motivation to remain awake activates orexin neurons
62
Q
What happens when there is an absence of orexin neurons?
A
- forms of narcolepsy
63
Q
What are the types of sleep disorders?
A
- narcolepsy
- insomnia
- fatal familial insomnia and sporadic fatal insomnia
- non-REM parasomnias
- REM sleep behaviour disorder
64
Q
What is narcolepsy?
A
- rare sleep disorder
- periods of excessive daytime sleepiness and irresistible urges to sleep
- death of orexin neurons
- attacked by the person’s own immune system
- adolescence or young adulthood
- sleep paralysis
- cataplexy
65
Q
What is sleep paralysis?
A
- when REM associated paralysis occurs just before a person falls asleep or just after they wake up
- often accompanied by vivid, dream-like hallucinations
66
Q
What is cataplexy?
A
- when complete muscle paralysis suddenly occurs when someone is awake
- typically precipitated by strong emotional reactions or sudden physical effort
67
Q
What is insomnia?
A
- difficulty falling asleep after going to bed or after awakening during the night
- affects approximately 25% of population occasionally
- 9% regularly
68
Q
What is fatal familial insomnia and sporadic insomnia?
A
- very rare disease
- progressively worsening insomnia
- hallucinations, delirium, confusional states, and eventually death
- progressive neurodegeneration around the thalamus, hypothalamus, and/or brain stem (sleep neurons degenerate, lose ability to sleep)
69
Q
What are non REM parasomnias?
A
- sleep disorders that occur during non-REM sleep or transitions out of sleep
- slow wave sleep, first half of night
- brain caught in between a sleeping and waking state
- people are unaware they exhibit this behaviour
70
Q
What are types of non-REM parasomnias?
A
- sleep walking
- sleep talking
- sleep groaning
- sleep crying
- sleep eating
- sleep masturbating
- sleep teeth grinding
- sleep terrors
71
Q
What are sleep terrors?
A
- overwhelming feelings of terror upon waking
- panic and screaming and bodily harm caused by rash actions
- sometimes have no recollection
- post-traumatic stress disorder
72
Q
What is REM sleep behaviour disorder?
A
- neurological disorder
- person does not become paralyzed during REM sleep
- acts out dreams
- neurodegenerative disorder with at least some genetic component
- associated with Parkinson’s disease
