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Neuro > EEG Sleep > Flashcards

EEG Sleep Flashcards

1
Q

Define sleep

A

State of unconsciousness from which an individual can be aroused by normal stimuli, light, touch, sound etc.
Is predictable and cyclical

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2
Q

Define coma

A

State of unconsciousness from which the individual cannot be aroused or not respond to stimuli
Is very complex

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3
Q

What does sleep deprivation cause?

A

Impaired cognitive function
Impairment of physical performance
Sluggishness
Irritability

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4
Q

What does sleep support?

A

Neuronal plasticity, learning + memory, cognition, clearance of waste from CNS, conservation of whole body energy and immune function
All can become compromised if poor sleep

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5
Q

Describe neuronal plasticity

A

Brains ability to change and adapt in response to learning and experience

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6
Q

How does sleep occur?

A

Due to inhibitory processes that originate in the pons
Activity originates in the reticular formation of brainstem - controls state of consciousness

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7
Q

Describe the function of reticular formation in sleep

A

Sends projection to thalamus and higher cortical areas
Arousal and sleep centres exist here and the level of consciousness depends on balance of these 2

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8
Q

What molecules are believed to contribute to sleep?

A

Delta sleep inducing peptides (DSIP)
Adenosine
Melatonin
Serotonin

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9
Q

How is the hypothalamus involved in sleep?

A

Hypothalamus and suprachiasmatic nuclei (SCN) are involved in induction of sleep
SCN activity demonstrates circadian rhythm - controls release of melatonin

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10
Q

Describe the inhibitory neurons in the SCN

A

Stimulated by light and act to inhibit the pineal glands which releases melatonin
Darkness removes the inhibition - feeling of sleepiness as melatonin released

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11
Q

What is circadian rhythm of melatonin release linked to?

A

Inhibition of Orexin

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12
Q

Describe orexin

A

Excitatory neurotransmitter released from hypothalamus - required for wakefulness
Orexin neurons are active during day and stop firing at sleep

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13
Q

What does defective orexin signalling lead to?

A

Narcolepsy - individual suddenly falls asleep

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14
Q

How does blocking serotonin formation inhibit sleep?

A

Many neurons within reticular formation are serotonergic - serotonin is precursor for melatonin

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15
Q

Describe serotonin reuptake inhibitors

A

Common treatment for depression when sleep disruption is often present
They increase serotonin levels in synapse

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16
Q

How is brain activity measured?

A

Recording patterns by Electroencephalogram EEG - electrodes placed on scalp to record activity in underlying neurons

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17
Q

What can the wave patterns on EEG be analysed by?

A

Amplitude and frequency

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18
Q

Describe frequency and amplitude with increasing neural excitement

A

Frequency - increases
Amplitude - decreases
Longer the wave length deeper into sleep and shorter is awake/alert

19
Q

What are the 4 main types of wave pattern seen?

A

Alpha
Beta
Theta
Delta

20
Q

Describe the alpha wave pattern

A

Associated with relaxed awake state
Is high frequency and medium amplitude waves

21
Q

Describe the beta wave pattern

A

Associated with alert awake state
High frequency and low amplitude waves

22
Q

Describe the theta wave pattern

A

Associated with early sleep
Low frequency waves which can vary enormously in amplitude

23
Q

Describe the delta wave pattern

A

Associated with deep sleep
Very low frequency but high amplitude waves

24
Q

How does Beta waves have low amplitude waves in awake state?

A

Increase in activity is asynchronous as brain doing so many things at once - opposing polarities of signals cancel each other out and not recorded on EEG

25
Q

How is it high amplitude in relaxed state?

A

Synchronised activity - so as signals are doing same thing, the amplitude of voltage change is large but slow frequency

26
Q

What is stage 1 of the sleep cycle?

A

Slow wave, non-REM, S-sleep
Slow eye movements , light sleep very early in sleep cycle
High amplitude and low frequency theta waves

27
Q

What is stage 2 of sleep cycle?

A

Eye movements stop
Frequency slows further but EEG shows bursts of rapid waves called sleep spindles

28
Q

What is stage 3 of sleep cycle?

A

Hight amplitude and low frequency delta waves interspersed with short episodes of faster waves and spindle activity declines

29
Q

What is stage 4 of sleep cycle?

A

Exclusively delta waves
Very slow and high amplitude
Deep sleep
From 4 then move back to 3 and 2 before REM sleep

30
Q

What is REM sleep?

A

Rapid eye movements - dreams occur
Low amplitude and and high frequency - similar to awake state

31
Q

What are the physiological characteristics of deep slow wave sleep?

A

Deep sleep happens in first hours of sleep
Most restful type of sleep
Associated with decreased vascular tone, resp. and basal metabolic rate
Hippocampus very active

32
Q

What follows initial slow wave sleep - stage 3 and 4?

A

Gradual awakening to stage 1 but not stage 1 - REM stage
Waves are desynchronised, high frequency and low amplitude

33
Q

Why does dreams mostly occur in REM?

A

Neural connection being made randomly and illogically

34
Q

Describe muscles during REM sleep

A

Eye muscles show rapid bursts of activity
Skeletal muscles are inhibited by inhibitory projections from pons to spinal cord - prevents acting out dreams

35
Q

What pathways is REM sleep dependant on?

A

Cholinergic pathways within reticular formation and projection to thalamus, hypothalamus and cortex
Anticholinesterases increase time in REM

36
Q

How long does REM last?

A

5-30 mins every 90 mins during normal nights sleep
Increasing in frequency and duration as night progresses

37
Q

How does sleep change over lifetime?

A

Total sleep time decreases
Percentage of REM also declines and can be absent from 80 year old +

38
Q

Describe insomnia

A

Defined as chronic inability to obtain the necessary amount or quality of sleep to maintain adequate daytime behaviour

39
Q

What is chronic primary insomnia?

A

Usually no identifiable psychological or physical cause

40
Q

What is temporary secondary insomnia?

A

In response to pain, bereavement or other crisis
Usually short lived

41
Q

Describe nightmares

A

Have a strong visual component and during REM sleep, typically occurring far on through the night
Have clear recollection of the dream

42
Q

Describe night terrors

A

Occur in deep, delta sleeps and common in age 3-8 years, typically early in the night
Child does not remember the episode -screaming and sit up

43
Q

Describe somnambulism

A

Sleep walking - occurs exclusively in non-REM sleep, mainly stage 4and more common in children and young adults
Appear awake

Neuro (40 decks)

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