Sleep Flashcards
(72 cards)
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
How is metabolic rate and body weight correlated?
- overall metabolic rate increases as mass increases
- metabolic rate per pound (or per cell) decreases as mass increases
26
What are the correlation of body mass, brain mass, metabolic rate, heart rate, life span, sleep time and length of sleep cycles?
- 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
What is an example of the correlations for large animals?
- low metabolic rates per cell
- long lifespans
- don't sleep much
- each sleep session is long
28
Why do all these correlations exist?
- 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
What are the main theories about why animals sleep?
- to recover from physical or mental exertion
- brain processing
- waste removal
30
What is the theory that animals sleep to recover from physical or mental exertion?
- 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
What is the theory that animals sleep for brain processing?
- 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
What is the short explanation of the brain processing theory?
- sleep housekeeping function to maintain network stability
- learn during day
- need to reorganize things offline
33
What is the theory that animals sleep for waste removal?
- 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
How does the waste removal in the brain work?
- 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
What is the glymphatic system?
- 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
Why didn’t animals just evolve bigger brains so CSF can diffuse around the brain and clear away waste all the time?
- 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
What is a circadian rhythm?
- 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
What happens if we shift the light cycle of rats?
- quickly adapt to change
39
What happens to rats if the light is constantly dim?
- maintain their circadian rhythms
- rhythms drift slightly over time
- a brief pulse of bright light can shift their internal clock
40
What is the suprachiasmatic nucleus (SCN)?
- of the hypothalamus
- regulates circadian rhythms
- receives a direct input from the retina (knows how much light)
41
What happens if the SCN is lesioned?
- 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
What is a biological clock?
- 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
What makes the clock of SCN neurons “tick”?
- 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
What is advanced sleep phase syndrome?
- 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
What is delayed sleep phase syndrome?
- 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
What is the sleep molecule hypothesis?
- 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
What is the adenosine molecule?
- 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
What is an example of an adenosine receptor antagonist?
- caffeine
49
What are the wake promoting signaling molecules?
- 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
What is orexin and histamine?
- neuropeptides
- released by neurons in the hypothalamus
51
What do histamine receptor blockers do?
- antihistamines
- often cause drowsiness
52
What does norepinephrine neuron activity mean?
- positively correlate with focus and attention
53
What does serotonin (5-HT) neuron activity mean?
- positively correlates with cortical arousal
- drugs that increase serotonin signaling tend to suppress aspects of REM sleep (without affecting memory)
54
What is the ventral lateral preoptic area (vlPOA)?
- 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
What happens if the vlPOA is lesioned?
- suppress sleep and cause insomnia
56
What do vlPOA neurons do?
- inhibit wake-promoting neurons
57
What is the sleep/wake flip-flop circuit?
- 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
When is the animal awake (according to flip-flop circuit)?
- when arousal, wake promoting system is more active than the vlPOA neurons
59
When is the animal asleep (according to flip-flop circuit)?
- when the vlPOA neurons are more active than the wake promoting arousal system
60
What does adenosine signaling do?
- 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
What is orexin?
- peptide produced by neurons in the lateral hypothalamus
- orexin neuron activity promotes wakefulness
- motivation to remain awake activates orexin neurons
62
What happens when there is an absence of orexin neurons?
- forms of narcolepsy
63
What are the types of sleep disorders?
- narcolepsy
- insomnia
- fatal familial insomnia and sporadic fatal insomnia
- non-REM parasomnias
- REM sleep behaviour disorder
64
What is narcolepsy?
- 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
What is sleep paralysis?
- 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
What is cataplexy?
- when complete muscle paralysis suddenly occurs when someone is awake
- typically precipitated by strong emotional reactions or sudden physical effort
67
What is insomnia?
- difficulty falling asleep after going to bed or after awakening during the night
- affects approximately 25% of population occasionally
- 9% regularly
68
What is fatal familial insomnia and sporadic insomnia?
- 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
What are non REM parasomnias?
- 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
What are types of non-REM parasomnias?
- sleep walking
- sleep talking
- sleep groaning
- sleep crying
- sleep eating
- sleep masturbating
- sleep teeth grinding
- sleep terrors
71
What are sleep terrors?
- 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
What is REM sleep behaviour disorder?
- 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
