EEG and Sleep - Karius Flashcards Preview

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Flashcards in EEG and Sleep - Karius Deck (31):

Gene activation/protein products set the circadian rhythm

Within the nucleus of SCN neurons

Clock (CLK)
BMAL1 - increase at night

Increase transcription/translation of:
Period genes (Per1-3)
Crytpochrome gene (Cry1-2)

Products inhibit Clock and BMAL1


Retina-Hypothalamic tract

light/dark information
-not vision
-use cryptochrome receptors

direct relay to hypothalamus, does not use visual cortex

Glutamate - daylight
Melatonin - darkness


Natural circadian clock

about 25 hours long - rough estimate


Hypothalamus role

controls circadian rhythm and sleep induction/arousal separately



Most time asleep is non-REM
Stages: 1, 2, deep
Progressive slowing of EEG waves

Dreams - rehashing days events, not remembered


REM sleep

rapid eye movement

EEG: low amplitude, higher frequency waves
-eyes moving rapidly left/right
-Associated with vivid dreams that you remember


Inducing sleep

Sleep homeostasis - need for sleep
-NREM sleep

Circadian clock tries to match need for sleep to darkness

Circadian clock triggers REM sleep

Ventral Preoptic Area (VPO) crucial


Mechanism of homeostatic need for sleep

PGD2 in blood bind to DP receptor on endothelial cell of capillary --> release of adenosine from cell into the CSF

accumulation of adenosine throughout day - tired feeling

Adenosine bind to 2a receptors in Ventrolateral Preoptic area (VPO)


Induction of sleep at non-REM level

IL1b, TNFa
NFkB released --> NO synthase --> NO

Tired when sick


Growth spurt induction of non-REM sleep

GHRH triggers growth during sleep

NFkB released --> NO synthase --> NO


Initiation of REM sleep

Lateral pontine tegmentum
-Cholinergic neurons

Axons to geniculate body - release Ach
-sends input to occipital cortex


Muscle paralysis in REM sleep

crucial to prevent muscle activation during dreams

Locus Ceruleus - descending inhibition to alpha-motoneurons
-effective on large muscle groups
-spares diaphragm and small muscle groups


Inducing arousal

lateral hypothalamus - orexin A and B (hypocretin 1 and 2)

orexigenic input sent to tuberomamillary nucleus (histamine)

Histamine released in locus ceruleus binds to H1 receptors, activating the LC neurons
-release NE and suppress REM sleep


EEG - general features

Low voltage less than 200 uV
Frequency less than 1 Hz to more than 50 Hz
Differs over different parts of brain

Changes with degree of activity in the brain, arousal/awareness, sensory input.

No distinct "pattern"
Clear "patterns" pathological - seizure


Alpha waves

8-13 hz
50 uV

quiet wakefulness - thinking with eyes closed

most prevalent over occipital cortex
disappear during sleep

-requires connection between thalamus and cortex
-GABAergic neurons "force" coordination of neuronal activity
-feedback oscillation between thalamus and cortex creates waves


Beta Waves

14-80 Hz
less than 50uV

alert wakefulness with eyes open

Most prevalent over frontal cortex, also parietal cortex

Origin: same as alpha
_sensory input disrupts oscillation to some extent


Alpha Block

With sensory input - opening eyes

alpha wave cease, alpha block or alerting response

beta wave begin

Will persist as long as alert

when eyes closed again, alpha waves reappear


Gamma Waves

30-80 Hz
Occur when aroused or focused on something

Replaced by even more irregular activity if plan a motor response

Require hippocampus


Theta Waves

4-7 Hz
100 uV

Normal in children - parietal and frontal cortex

Adults - frustration or disappointment

Occur in sleep

Origin -
Hippocampus required, involved in production


Delta waves

less than 3.5 Hz
100-200 uV

-deep sleep in adults
-appearance during "wakefulness" sign of serious organic brain disease

- does not require connection between thalamus and cortex
-feedback oscillation within cortex creates waves
-indicate cortex is not longer connected to thalamus


EEG in infancy to childhood

fast beta-like activity
over occipital region slow 0.5 - 2.0 Hz activity

Activity over occipital region gradually increase in frequency throughout childhood

adult alpha-wave appear during adolescence


Factors decreasing frequency of alpha rhythm

Low body temperature
low adrenal glucocorticoids
high PaCO2


Sleep cycle patterns

First cycle of night:
-70-100 minutes in duration
-then moves to REM (short)

Later cycles:
-90 min cycle length
-less time in deep sleep, more in REM


Sleep cycles in children

More time in REM
More time in deep sleep
More total sleep time


Sleep cycles in elderly

Fewer REM epochs (but they can be long)
almost no deep sleep
More frequent awakenings
Less total sleep - more likely to nap
Circadian rhythm is not a strong as it once was


Slow wave sleep on EEG

Stages N1, N2, N3

characterized by slowing of EEG



stage 1 equivalent

drowsiness/earliest stage of sleep

Physical characteristics:
-slow rolling movements of the eyes
-EMGs show muscle activity

EEG characteristics:
Low voltage EEG
slowing of frequency



Stage 2 equivalent

True sleep

Physical characteristics:
EMGs show muscle activity, but relatively quiet

EEG characteristics:
Increasing voltage EEG
Slowing of frequency
Sleep spindles


Sleep spindles

Begin to appear in N1, but are most prominent in N2

Bursts of alpha-like activity interrupting the slower EEG of sleep

Often preceded by a sharp wave (K complex)


Deep Sleep

N3 in current guidelines

True sleep

Physical characteristics - deep sleep

EEG characteristics -
increasing voltage EEG
Slowing of frequency - theta and delta waves prominent


REM sleep

Physical characteristics
-rapid side to side eye movements
-EMG becomes very quiet - locus ceruleus suppresses

EEG characteristics -
-rapid, low-voltage
-similar to beta waves