Sleep Flashcards
What does an EEG measure?
changes in electrical activity of different locations in the cerebral cortex’s
Why are EEGs used?
simple and non-invasive
used for research and in clinical settings to diagnose
What determines the amplitude of an ECG wave?
the synchronicity of the neurons firing
more inputs firing in a narrow time window the pyramidal cells response will be synchronized resulting in a larger EMG amplitude (stronger)
Where does the EMG signal originate from?
measures voltage differents in synaptic inputs in the apical dendrites from pyramidal cells
active synpase on the dendrite causes the afferent axon to fire, presynaptic terminal releases glutamate which opens the cation channel -> positivge current flows inot dendrite = slightly negative ECF
current spreads deeper leaviing the fluid slightly positive
EEG electrode measues this pattern
What is the relationship between frequency and amplitude of EEG rythyms?
low frequency + high amplitude = deep sleep/coma
high frequency + low amplitude = alert/awake
What are delta rhythms?
<4 Hz large in amplitude
a hallmark of deep sleep
What are theta rhythms?
4-7 Hz both sleeping and waking states
What are alpha rhythms?
8-12 Hz associated with quiet,waking states
What are gamma rhythms?
30-90 Hz
signal an activated or attentive cortex
What are spindles?
brief 12-14 Hz waves
associated with sleep
What are ripples?
brief bouts of 80-200 Hz oscillations
What was found when measuring EEGs in different mammals?
characteristics are similar across mammals despite large differences in brain mass
What are the two ways synchronous rhythms can be generated?
- central neuronal pacemaker setting the rhythm
- timing arises from collective behaviour of a network of neurons
What is a two neuron oscillator?
one excitatory cell and one inhibitory cells synapse on eachother
with a constant excitatory drive onto the E cell, activity will trade back and forth between the two neurons -> generate a pattern of firing
What is a one neuron oscillator?
thalamic neurons fire in rythmic patterns that do not affect their input
a short pulse of stimulus applied results in rythmic firing first with bursts and then single spikes
Why can the thalamus maintain rythmic firing on its own?
its particular set of voltage gates channels
What drives the rythyms in the cerbral cortex?
the thalamas
thalamic neurons
How do thalamic neurons synchronize with the cortex neurons?
thalamic neurons synapse on cortical neurons which also synapse back onto the thalamic neurons (excitatory)
inhibitory thalamic neurons force neurons to conform to the group to create synchronicity
What doe quiet and whisking states in mice correspond to in regards to synchronicity?
synchronized during quiet states (no information processing)
unsynchronized during whisking states (information processing)
What is the behavioural definition of sleep?
sleep is a readily reversible state of reduces responsiveness to, and interaction with, the environement
What are the stages of sleep?
waking
stage 1
stage 2
stage 3 (slow wave sleep)
REM sleep
What are characteristics of waking?
an alert awake humans EEG is desynchronized
mix of high frequencies with low amplitude
beta activity
What are characteristics of stage 1 of sleep?
alpha rhythms appear during relaxation
sharp waves calles vertex spikes appear
lower amplitude, decreased HR muscle tension
slow eye rolls
afew minutes
What are characteristics of stage 2 of sleep?
brief peridos of sleep spindles and K complexes
What are characteristics of stage 3 of sleep?
large slow delta waves
deepest level of sleep
thalamas dominates = synchronizes large waves
What are characteristics of REM sleep?
deep muscle relaxation
EEG activity similar to waking waking
rapid eye movements (saccades)
What stages of sleep are NREM?
Waking
Stage 1
Stage 2
Stage 3 (SWS)
How is NREM sleep characterized?
slow rolling eye movements (stage 1) followed by decreases in muscle tone, body movements, heart rate, breathing, blood pressure, metabolic rate, and temperature
all parameters reach their lowest during SWS (stage 3) sleep
How is REM sleep characterized?
rapid ballistic eye movementrs as well as by pupillary constriction, paralysis of many large muscle groups, and the twitching of smaller muscles in the fingers, toes and middle ear
blood pressure, heart rate, and metabolism increase to levels almost as high as in awake state
What is the sleep cycle?
start with transition fromm awake to stage 1then progress through deeper stages of NREM sleep then into REM sleep
repeated seversl times (~100 mins) but each cycle has shorter shallower NREM periods and longer REM periods
How do sleep patterns change with age?
With increasing age the amount of total sleep and REM sleep decreases
What are characteristics of infants sleep patterns?
stable patterns don’t appear until about 16 weeks
they can move into REM sleep from awake
Large amount of REM sleep and total sleep
What are characteristics of elderly sleep patterns?
can fall asleep but not stay asleep
frequent awakenings
severe reduction in stage 3 sleep -> diminishes cogntive abilty
