B7.048 Sleep, Wakefulness, and the EEG

Question 1

components of reticular activating system

Answer 1

cerebral cortex
thalamic nuclei
-intralaminar nuclei
-thalamic reticular nucleus
pontomesencephalic reticular formation

Question 2

function of reticular activating system

Answer 2

diffuse projecting system
turns on brain
heavily involved in wakefulness and sleep

Question 3

segments of the reticular formation

Answer 3

stuff in between CN nuclei and long tracts
rostral reticular formation
caudal reticular formation
-raphe
-medial (magnocellular)
-lateral (parvocellular)

Question 4

what is an EEG

Answer 4

electroencephalogram
measures electrical activity in brain with sensitive electrodes
produces a graph of voltage (uV) by time

Question 5

EEG frequency bands

Answer 5

beta: >12 Hz
alpha: 8-12 Hz
theta: 4-8 Hz
delta: <5 Hz

Question 6

2 EEG activities seen during wakefulness

Answer 6

B activity, > 20 Hz

a activity, 8-12 Hz

Question 7

beta activity

Answer 7

low amplitude
high frequency
occurs during alert wakefulness
front of brain

Question 8

alpha activity

Answer 8

higher amplitude
lower frequency
relaxed wakefulness with eyes closed
back of brain

Question 9

distribution of alpha and beta waves over the brain

Answer 9

alpha rhythm largest over parietal, occipital, and posterior temporal lobes
alpha replaced by beta when eyes are opened
beta rhythm most prominent in front of brain

Question 10

current source of EEG

Answer 10

cortical neurons
changes in RESTING membrane potentials
-synaptic potentials
-summed EPSP and IPSP
NOT action potentials (too brief)

Question 11

synchronization of cortical neurons

Answer 11

if resting membrane potential oscillations of cortical neurons were independent and random, electrical activity would cancel out
a pacemaker is required to synchronize the oscillations

Question 12

pacemaker of cortical neurons

Answer 12

thalamic reticular nucleus

thalamocortical circuits

Question 13

how does the thalamic reticular nucleus operate

Answer 13

receives excitatory input from the thalamocortical and corticothalamic axon collaterals
neurons are GABAergic

Question 14

reticular activating system (RAS) input to thalamus (TRN)

Answer 14

regulates wakefulness
thalamus synchronizes the oscillations of cortical neurons at different frequencies during wake and sleep
EEG appearance changes

Question 15

sleep stages

Answer 15

awake: a and B
stage 1 (drowsy): a drops out, theta waves
stage 2: sleep spindles and k-complexes
stages 3-4: slow wave sleep, D waves
REM sleep: looks like awake, B waves

Question 16

REM sleep

Answer 16

metabolically active brain

EEG appearance similar to awake EEG

Question 17

brain during non REM sleep

Answer 17

less physiologically active

prominent slow waves

Question 18

synchronized waves

Answer 18

high amplitude
low frequency waves
sleep spindles, a, and D rhythms

Question 19

desynchronized waves

Answer 19

low amplitude
high frequency
b rhythm

Question 20

neuronal physiology during wakefulness and REM

Answer 20

neuron depolarizations with short refractory periods

tonic mode

Question 21

neuronal physiology during slow wave sleep

Answer 21

stimulus from RAS results in hyperpolarization
post stimulation latency period so that neuron cannot be stimulated again
phasic mode

Question 22

the sleep cycle

Answer 22

descends from stage 1, 2, 3, 4 back up to REM and then back down
90 minute cycles throughout the night
REM cycles become longer closer to morning

Question 23

when is a person most likely to spontaneously awake from sleep

Answer 23

after a REM cycle

Question 24

changes to the sleep cycle with age

Answer 24

older people have less time in slow wave sleep
more fragmented
more waking up

Question 25

physiologic characteristics of slow wave sleep

Answer 25

neuronal activity low, metabolic rate and brain temp at their lowest
sym output decreases, HR and BP decline
muscle tone low, but present
reflexes present

Question 26

physiologic characteristics associated with REM sleep

Answer 26

rapid eye movements
dreaming
high cortical activity
irregular changes in BP, HR , and breathing
penile erection, clitoral engagement
atonia

Question 27

explain atonia in REM sleep

Answer 27

active inhibition of alpha motoneurons prevents movements
occasional jerky movements escape
reticulospinal tract responsible for this inhibition (so you don’t act out your dreams)

Question 28

REM sleep disorders

Answer 28

reticulospinal dysfunction
muscles don’t shut down
common in people with dopaminergic issues, may later get Parkinson’s

Question 29

diffuse projection systems involved in regulation of wakefulness and sleep

Answer 29

cholinergic
noradrenergic
serotonergic
dopaminergic

Question 30

cholinergic projection system

Answer 30

important component of reticular activating system (RAS)
located in basal nucleus of the forebrain, rostral pons, and midbrain tegmentum
ACh causes depolarization of forebrain neurons, thus causing cells to discharge in the tonic move which results in desynchronized EEG
keeps you awake

Question 31

noradrenergic system

Answer 31

locus ceruleus

wakefulness and REM sleep

Question 32

serotonergic system

Answer 32

median raphe of reticular formation

slow wave sleep maintenance

Question 33

effect of serotonin inhibition drugs

Answer 33

can cause insomnia

Question 34

dopaminergic system

Answer 34

substantia nigra

deficiency: REM sleep disorder

Question 35

circadian rhythm

Answer 35

sleep and wakefulness occur in an approximate 24 hours cycle (25-26ish for most)
rhythm is entrained by exogenous stimuli (visual input)

Question 36

circadian rhythm pacemaker

Answer 36

suprachiasmatic nucleus in anterior hypothalamus
monitors light/dark cycle
receives input from retino-hypothalamic tract

Question 37

retino-hypothalamic tract

Answer 37

light sensitive retinal ganglion cells contain melanopsin

these cells go straight to hypothalamus SCN > pineal gland > melatonin