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N - C > EEG and Sleep > Flashcards

EEG and Sleep Flashcards

1
Q

What are States of Consciousness?

A

Refers to whether a person is awake or asleep etc
(in normal health)
Involves conscious experience

There are infact a very broad range of states

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2
Q

What is a conscious experience?

A

Things a person is aware of

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3
Q

What are the are the States of Awareness (Conscious States)?

A 
Normal consciousness
Delirium
Dementia
Confusion
Chronic vegetative state
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4
Q

What is normal consciousness?

A

Aware of self and external environment

Well orientated and responsive

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5
Q

What is delirium?

A 
Disorientation, 
Restlessness, 
Confusion, 
Hallucinations, 
Agitation 
Alternating with other conscious states (wild oscillations)

May develop in high fever or with certain drugs

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6
Q

What is dementia?

A 
Difficulties with: 
Spacial orientation
Memory
Language
Changes in personality

Often seen in elderly patients

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7
Q

What is confusion?

A

Reduced awareness,
Easily distracted
Easily startled by sensory stimuli
Alternates between drowsiness and excitability

Often seen in elderly patients

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8
Q

Whst is somnolence?

A

Extreme drowsiness, but will respond normally to stimuli

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9
Q

What is Chronic Vegetative State?

A

Conscious, but unresponsive, no evidence of cortical function

“Locked in syndrome”

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10
Q

What are the States of Awareness (Unconscious States)?

A 
Asleep
Stupor
Coma
Delirium
Dementia and Confusion
Coma
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11
Q

What is being asleep (In terms of states of awareness)?

A

Can be aroused by normal stimuli, light, touch, sound etc

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12
Q

What is stupor?

A

Can be aroused by extreme and/ or repeated stimuli

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13
Q

What is a coma?

A

Cannot be aroused and does not respond to stimuli,
(coma states can be further divided according to the effect on reflex responses to stimuli)

Is not deep sleep
Not cyclical
Complex

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14
Q

How can normal consciousness vary?

A

Varies enormassly from being:

  • “awake” = like you are first thing in the morning
  • AWAKE = High Sympathetic Drive (being chased or shot at)
  • Evereything in between
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15
Q

How may you assess the level of consciousness in an awake person?

A

Looking at their behaviour, general alertness, speech patterns, sppech content, reading, writing and calculating skills. Spell words backwards
(Sensitivity to cultural aspects)

GCS used to assess level of consciousness, followning brain injury (Eyes, verbal, motor)

Measure pattern of brain activity i.e. EEG (ElectroEncepheloGram) is an important tool in identifying the state of consciousness.

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16
Q

How do EEGs make recordings?

A

Use electrodes on the scalp to record the activity of underlying cells.

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17
Q

How can activity in an EEG be analysed?

A

In terms of:

  • Amplitude: The bigger the wave the more activity of the cells is synchronised
  • Frequency: The higher the frequency, the faster the rate of fluctuations in the cortical cells.
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18
Q

How is the awake state characterised in the EEG?

A

Low amplitude

High frequecy waves

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19
Q

What two rhythms can the awake state be divided into?

A

alpha rhythm (8-13Hz):

  • Relaxed state (i.e. when you close your eyes and shut off alot of your sensory information)
  • Rhythm becomes slower and greater in amplitude

beta rhythm (>13Hz up to 30Hz):

  • Very alert state
  • Even higher freqency and smaller amplitude
20
Q

Explain why an alert brain has high freqeuncy, low amplitude and a reflaxed brain -> low freqeuncy, high amplitude

A

In a relaxed brain, different cells are all doing the same thing through a gentle cycle = synchronised. All their amplitudes add up and you get high amplitude, low frequency

In an alert brain, cells are busy all doing different things rapidly = desynchronised, so EEG has a low amplitude but high frequency

21
Q

What other two brain rhythms are there appart from alpha and beta?

A

Theta (4-8Hz):
-Theta brain waves are present during light sleep, including REM. It is the realm of your subconsciousness and only experienced momentarily as you drift off to sleep from Alpha and wake from deep sleep (from Delta).

Delta (

22
Q

How did people view sleep in the past compared to today?

A

Until 1950s people thought that sleep was passive i.e. fall asleep because nothing to keep you awake.

Not True. Sleep shows a circadian rhythm and is itself cyclical, there are successive periods of different stages of sleep.

23
Q

Describe the two types of sleep

A

REM sleep, D-sleep, paradoxical sleep:
-During which there is Rapid Eye Movements

Slow Wave, non-REM, S-sleep
-Without Rapid Eye Movement

During S-wave sleep there is a gradual increase in amplitude of EEG waves as the activity of more and more of the cells are synchronised and the frequency is slow.

24
Q

Describe the stages of sleep

A

4 stages of sleep
During deep S-sleep (Stage 4) the physiological signs are:
-Relaxed but postural adjustments occur every 20 minutes or so
-Parasympathetic dominance increases (decreased HR)
-Difficult to arouse someone from Stage 4 S-sleep

25
Q

What happens once we enter stage 4 sleep during the sleep cycle?

A

Following initial S-wave sleep. there is a gradual awakening towards Stage 1, but not like the initial stage 1, instead REM sleep during which EEG waves are Desynchronised, high frequency, low amplitude, very like the awake state.

26
Q

What are the physiological signs of REM sleep?

A
  1. Profound inhibition of body muscles as if the motor system has been turned off
  2. EXCEPT for eye muscles which show bursts of activity
  3. Hardest state of all to rouse someone from, even though the EEG is like that of the awake state (paradoxical sleep).
    (you do get spontaneous awakening however)
  4. Sympathetic dominance: increased HR and BP, increased cerebral blood flow and brain temperature
  5. > 90% of people report dreaming if awakened from REM sleep.
  6. All mammals and birds have REM sleep
    (except dolphins and spiny ant eaters)
27
Q

What is the typical nights sleep for a young adult?

A
  1. First REM period is short, 5-10 minutes. REM duration increases as night progresses.
  2. S-sleep becomes shallower. All Stage 3 and 4 S-sleep (= Delta sleep) occurs in the first half of the night = restorative, repairing sleep, increased Growth Hormone (20 fold increase)
28
Q

How does sleep change in terms of development?

A
  1. Total sleep time decreases rapidly through childhood and adolescence.
  2. Percentage of REM sleep also declines:
    - 80% in 10 week premature infant
    - 50% at full term declining to a stable…
    - 25% in adulthood

-May be absent in senescence, >80 years old

29
Q

How does the timecourse of change in REM signify its importance?

A

Does the time course of change in REM sleep parallel brain maturation and the formation of functional synapses?

Obvious need in development, but why adults?
Is REM sleep needed in other situations where synaptic plasticity is important e.g. memory?

30
Q

How common are sleep disorders?

A

Very

May affect up to 25% of the population

31
Q

What is the most common sleep disorder?

A

Insomnia

Affects around 33% of adults

32
Q

What are the two types of Insomnia?

A

Termprary Insomnia:
-As the result of a bereavement or other crisis

Chronic Insomnia:
-“Chronic inability to abtain the necessary amount or quality of sleep to maintain adequate daytime behaviour”

Important to distinguish between the two

33
Q

Do insoniacs actually get less sleep?

A

127 self-confessed insomniacs studied in a sleep laboratory.
Their mean sleep duration was 7 hours and their mean onset time to sleep was 15 mins compared with average 8 hours sleep and 10 minutes onset time.

When they woke they denied they had slept and had to be shown footage and data to be convinced otherwise

SO THEY DO SLEEP, DREAM AND SNORE

34
Q

What may cause insomnia?

A

Association of negative feeling with their normal sleep environment (may result in better sleep experience in a laboratory).
Perhaps they dream they are awake.

35
Q

How do you treat insomnia?

A

The underlying anxiety/ depression should be tackled not the percieved symptoms of insomnia.

Sleeping pills should only be considered in temporary insomnia.
No-one should be on these long term

36
Q

Why should sleeping pills (esp barbiturates) not be prescribed in chronic insomnia?

A

Many hypnotic drugs especially barbiturates depress REM and Delta sleep.
(Decrease waking up during night in short term (initially))

Drug withdrawal -> “rebound effect” where there is a marked and immediate increase in the quantity of REM sleep, as if to catch up.

37
Q

Why are barbiturate withdrawals hard in patients who have been prescribed them for insomnia?

A

Rebound effect where patients expereince massive increase in REM sleep as if to catch up

This brings a large increase in experience of nightmares

38
Q

How does the rebound effect indicate the importance of REM sleep?

A

Whenever deprived of REM sleep there is always this catch up when able to sleep again.

This catch up isnt seen with Delta sleep (gradual increase back to normal)

Therefore indicates that REM must have an important physiological function

39
Q

What alternative to barbiturates are there in terms of sleeping pills?

A

Benzodiazepines have less effect on REM sleep but are addictive and cause many problems on withdrawal

Sleeping pills should NOT be given chronically

40
Q

What are nightmares?

A

Nightmares have a strong visual component and are seen during REM sleep when PGO (pontine-geniculo-occipital) spikes can be recorded

The shut off of the motor system may be to prevent us from acting out our dreams

41
Q

What are PGO waves (spikes)?

A

Ponto-geniculo-occipital waves or PGO waves are phasic field potentials. These waves can be recorded from the pons, the lateral geniculate nucleus (LGN), and the occipital cortex regions of the brain, where these waveforms originate. The waves begin as electrical pulses from the pons, then move to the lateral geniculate nucleus residing in the thalamus, and then finally end up in the primary visual cortex of the occipital lobe. The appearances of these waves are most prominent in the period right before rapid eye movement sleep (or REM sleep), and are theorized to be intricately involved with eye movement of both wake and sleep cycles in many different animals.

42
Q

What can happen in REM behaviour disorder?

A

The motor shut off that occurs during REM doesn’t occur and patients act out their dreams.

This can cause serious accidents and murder

43
Q

What are nighterrors?

A

Night terrors are associated with intense feelings particularly of fear and are non-REM phenomena

Common in post-traumatic stress syndrome

44
Q

What is Somnambulism?

A

Sleep walking
Occurs exclusively in non-REM sleep, mainly in Stage 4 sleep.

In view of the decline in Stage 4 sleep with age, its not suprising that it mainly affects children (predominantly boys)

Somnambulists walk with their eyes open and avoid objects but have no recall of the episode if awakened

45
Q

What is narcolepsy?

A

(0.04-0.09% of population)
Irresistable urge to sleep, attacks last 5-30 minutes, usually during day and at behaviourally inappropriate times.

May be precipitated by feelings of strong emotion (e.g. during laughter or sex)
Often enter durectly into REM sleep

Usually cataleptic as well (i.e. abrupt loss of muscle tone, but remain conscious). Effectively symptoms could be interperated as intrusion of REM sleep characteristics onto the waking cycle

VERY DANGEROUS BCEAUSE OF ACCIDENT RISK

46
Q

What is the cause of narcolepsy?

A

Cause has recently been linked to a hypothalamic neurotransmitter, orexin (aka hypocretin), which stimulates wakefulness and shows cyclic levels in blood, with a decrease at night.

Post-mortem brains of patinets with narcolepsy have been shown to have an approximate 90% loss of orexin producing neurones.
So, possibility of treatment now available.

(Orexin also stimulates appetite)

N - C (35 decks)

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