Sleep Flashcards
What is the wave frequency of alpha activity?
8-12 mhz
What is measured in sleep studies?
EEG [brain] EMG [muscle - chin] EOG [eyes] skin [conducting electricity] heartrate
What is wave frequency of Beta activity?
13-30 mhz
What is wave frequency of Theta sleep?
4-11.5 mhz
What is wave frequency of Delta sleep?
0-3 mhz
What is slow wave sleep?
delta - 0-3 mhz
What is the down state?
period of inhibition during slow oscillation in slow-wave sleep; neurons in neocortex are silent and resting
What is up-state in sleep?
Period of excitation during slow oscillation in slow wave sleep; neurons in neocortex briefly fire at high rate
What is indicated by lower frequency activity in brain?
Neurons are synchronising more
What do sleep spindles do?
Appear 2-5 times / minute in stages 1-4
consolidating memories,
correlation between sleep spindles and intelligence
What are K complexes?
Found only in stage 2 sleep
1/minute, triggered [not only] by loud noises
forerunners of delta activity
What is stage 3 sleep?
Contains 20-50 % delta activity
What is stage 4 sleep?
Contains >50% delta activity
What is slow wave sleep?
Stages 3-4
delta activity
What is most important part of slow wave sleep?
slow oscillations - <1Hz
consisting down state [neurons resting] and up state [period of excitation where neurons fire at high rate]
What happens approx 90 minutes into sleep cycle?
Neurons desynchronise; sprinkling of theta [stage 1] waves
eye movement
profound loss of muscle tone [EMG silent]
What happens when someone is aroused from REM sleep?
Alert and awake
Describe arousal from REM sleep?
Will respond to meaningful stimulation - eg name; awake and alert
What do people who are aroused from slow wave sleep report?
presence of thought, image, emotion
How many periods of REM sleep are in 8 hour block?
4-5
When do blocks of slow wave sleep happen?
Early in night [normally 2x stage 4, 4x stage 3]
What happens to brain in REM sleep?
cerbral blood flow and oxygen consumption are accelerated
increased activity
What happens to body in REM sleep?
Spinal and cranial motor neurons inhibited
Body paralysed
What happens to length of REM sleep periods over course of sleep?
Get longer
What are principle characteristics of Slow wave sleep?
EEG synchrony [slow waves]
Moderate muscle tonus
Slow or absent eye movements
Lack of genital activity
What are principle characteristics of REM sleep?
EEG desynchrony [rapid, irregular waves] Lack of muscle tonus REM Penile erection or vaginal secretion Dreams
During REM sleep, what happens to blood flow?
High in visual association cortex
Low in primary visual cortex and prefrontal cortex
What does high rate of blood flow in visual association cortex indicate?
visual hallucinations - dreams
What does low blood flow to prefrontal cortex in REM sleep create?
Confabulation, distortion of reality in dreams
Lack of time / organisation in dreams
What do REM sleep eye movements relate to?
Visual imagery in our dreams
What happens to other brain mechanisms [eg motor mechanisms] when we dream?
Become active if they are active in dream [eg increased blood flow to cortical and subcortical motor mechanisms]
What happens if a dream involves talking or listening?
Those parts of brain become active
What mental activity can accompany slow wave sleep/
Nightmares
How many people are affected by insomnia?
Approx 25% occasionally, 9% regularly
What are problems caused by chronic sleep deprivation?
increased risk of obesity, diabetes, cardio-vascular disease
What are problems with sleep medication?
produces grogginess and difficulty concentrating next day
What is sleep apnea?
Inability to sleep and breathe concurrently
What does sleep apnea do to blood?
Lack of breathing –> increased carbon dioxide in blood –> stimulates chemoreceptors [neurons that detect certain chemicals], and person wakes up gasping for air
What causes sleep apnea?
Low muscle tone in airways
Narrowness in airways
What is narcolepsy?
Periods of irresistible sleep, attacks of cataplexy, sleep paralysis and hypnagogic hallucinations
What is a narcoleptic sleep attack?
Overwhelming urge to sleep that can happen at any time
What happens in cataplexy?
Muscle weakness [sometimes completely paralysed] while fully conscious
What causes cataplexy?
muscle paralysis [part of REM sleep] happens at inappropriate time
What precipitates cataplexy?
Strong emotional reactions or physical effort - esp if caught unaware
Why do people with narcolepsy try to avoid strong emotions?
Can trigger cataplectic attacks
What is sleep paralysis?
Inability to move just before onset of sleep, or waking in the morning
How can person be brought out of sleep paralysis?
By being touched; called by name
What are hypnogogic hallucinations?
Dreaming while lying awake, paralysed [sleep paralysis + dreaming + awake]
What is cause of narcolepsy?
Loss of orexinergic neurons [orexin peptide found in neurons with cell bodies in hypothalamus - destruction of these neurons causes narcolepsy]
what treats narcolepsy?
Ritalin
Antidepressants [facilitating serotonergic and noradrenergic activity]
What is REM sleep behaviour disorder
Behaviour of people corresponds with content of dreams
What causes REM sleep behaviour disorder?
Body fails to become paralysed in REM sleep
What treats REM sleep disorder?
Drugs
What are problems associated with slow wave sleep?
Bedwetting
Sleepwalking
Night terrors
Do all animals show signs of sleep?
All show periods of quiescence that resemble sleep
Only mammals and birds show REM sleep with muscle paralysis, EEG desynchrony and REM.
what have studies shown about physiological stress and relation to sleep deprivation?
No evidence
WHat have studies shown about relationship between body and sleep?
Primary role of sleep doesn’t seem to be rest and recuperation
What have studies shown about relationship btwn cognitive ability and sleep?
Cognitive ability can be affected by lack of sleep
What stages of sleep have been shown to be more important in studies?
REM and stage 4
What is relationship between activity of brain region during waking hours and activity during slow wave sleep?
Higher activity during waking show highest levels of delta waves [and lowest metabolic activity] during slow wave sleep
What does presence of slow wave activity in a brain region indicate?
Resting
What does waking up groggy and confused indicate?
Cerebral cortex shut down, not resumed functioning
What happens to cognitive abilities after missing a night’s sleep?
Impaired
What do lowered rates of metabolic activity in brain allow?
Restorative mechanisms in cells destroy free radicals [waste products produced by metabolic waking activity of brain]
What is impaired in fatal familial insomnia?
Thalamus
What are symptoms of fatal familial insomnia?
deficits in attention and memory –> dreamlike, confused state
loss of control of ANS and endocrine system
increased body temperature
insomnia
What are first signs of fatal familial insomnia?
Reductions in sleep spindles and K complexes
–> eventually slow wave sleep disappears, and only brief episodes of REM remain
What was shown in Huber’s study where people performed motor learning task just before sleep?
Increase in slow-wave activity in region of the neocortex that was active while performing the task.
Where is slow wave activity increased after day of cerebral activity?
Cerebral cortex
What happens after several days of REM sleep deprivation?
rebound phenomenon - much greater percentage than normal of REm sleep
What does REM rebound phenomenon suggest?
That REM sleep is controlled by a regulatory mechanism
What type of memory does REM sleep facilitate?
Non-declarative memory
What type of memory does slow wave sleep facilitate
Declarative
What does slow wave sleeping brain do?
Rehearses [consolidates] information acquired in previous period of wakefulness
What does prolonged wakefulness do to levels of glycogen in brain?
Decreases level
What does a fall in levels of glycogen do to adenosine?
Increases levels of adenosine
What does extracellular adenosine do?
Inhibits neural activity - therefore is a sleep-promoting substance
What is relationship of adenosine to sleep?
Extracellular adenosine [caused by depleted levels of glycogen] promotes sleep
What is effect of increased adenosine, caused by prolonged wakefulness
Inhibition of neural activity; produces cognitive and emotional effects seen in sleep deprivation.
What does caffeine do to adenosine receptors?
Blocks them, therefore decreasing tendency to sleep
What neurotransmitters play a role in arousal?
Acetylcholine, norepinephrine, serotonin, histamine, orexin
[ANSHO]
Where is acetylcholine most active?
Cerebral cortex
What is adenosine?
A neuromodulator released by neurons engaging in high levels of metabolic activity
What do acetylcholinergic neurons in pons and basal forebrain do when stimulated?
Produce activation and cortical desynchrony
What do acetylcholinergic neurons in medial septum do?
Control activity of hippocampus
What do acetylcholinergic agonists do on EEG?
increase cortical arousal
What do acetylcholinergic antagonists do on EEG?
decrease signs of cortical arousal
What happens to levels of ACh in waking, REM sleep and slow wave sleep?
High during waking and REM sleep
Low during slow wave sleep
What happens when dorsal pons is stimulated?
Increases activity in cerebral cortex
increases release in ACh in cerebral cortex
What type of NT are amphetamines agonistic for?
Catecholamines [eg NE]
What happens when ACH neurons in basal forebrain are activated by drugs?
Increases wakefulness
What is relationship of Norepephrine to arousal?
increasing NE neurons in Locus Coeruleus [dorsal pons] increases vigilance
What is relationship of serotonin to arousal?
Facilitate continuous, automatic movements [pacing, chewing]
Where are serotonin neurons found?
Raphe nuclei
What NT facilitates ongoing activities, and suppresses sensory information?
Serotonin
What happens to serotonergic neurons during sleep?
Firing rate declines in slow wave sleep, virtually zero in REM sleep, very active at immediate end of REM
Where are histaminergic neurons located?
TMN in hypothalamus
What is activity of histaminergic neurons during waking and sleeping?
High during waking
Low during slow wave and REM sleep
What does infusion of histamine into basal forebrain region do?
Increases wakefulness, decrease in non-REM sleep
What three factors control sleep?
Homeostatic, allostatic and circadian
What is the homeostatic control of sleep?
Desire for regular amount of sleep, repayment of sleep debt
What is allostatic control of sleep?
Reactions to threats in environment that override homeostatic factors
What are circadian factors in sleep?
Restriction of sleep to certain parts of day / night
What is the primary homeostatic factor in control of sleep?
Presence or absence of adenosine [accumulates in wakefulness, destroyed in slow wave sleep]
What is zeitgeber?
A stimulus [usually light of dawn] that resets the biological clock resposnible for circadian rhythms
What is a circadian rhythm?
A daily rhythmical change in behaviour or physiological processes
Where is the primary biological clock located?
SCN [suprachiasmatic nuclus] of hypothalamus
What do lesions of the SCN cause?
Disruption of daily rhythms [eating, sleeping] - though similar amount of sleep required [doesn’t override homeostatic control]
What visual fibers project to SCN?
retinal
What is melanopsin?
Photopigment in ganglion cells whose axons transmit info to SCN and the thalamus
Where do efferent axons of SCN terminate?
in subparaventricular zone [SPZ] [just dorsal to SCN]
What do lesions of the ventral part of SPZ cause?
disruption to circadian rhythms of sleep and waking
How do projections from dorsomedial nucleus of hypothalamus stop sleep?
inhibitory projections of the vIPOA and excitatory projections to the orexinergic neurons [promoting wakefulness]
Work diurnally
What provides evidence of chemical communication between SCN and other parts of brain?
Transplants of SCN
What is intercellular ticking [of internal clock] caused by?
Time it takes to produce and degrade a set of proteins
What happens to proteins in cells when they are exposed to light?
Changes the levels - therefore resetting the internal clock
What is relationship between testosterone and light?
increased length of day = higher testosterone
What hormone does the pineal gland secrete?
Melatonin
What is relationship between length of night and amount of melatonin secreted?
Longer the night, more melatonin secreted
What is the one neural connection the SCN relies on?
the SCN - PVN connection –> release of melatonin through pineal gland
What do lesions in SCN, PVN and pineal gland lead to?
Reduction in melatonin
