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Neuro Physiology > EEG, Sleep and Circadian Rhythms > Flashcards

EEG, Sleep and Circadian Rhythms Flashcards

1
Q

Why does sleep occur?

A

Due to inhibitory processes that originate in the pons

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2
Q

What does sleep do?

A

Dampens down the activity of the cortex

Puts us into a temporary state of unawareness

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3
Q

Activity of sleep originates where?

A

Reticular formation of the brainstem

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4
Q

Many neurones within the reticular formation are what?

A

Serotonergic

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5
Q

What is serotonin a precursor for?

A

Melatonin

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6
Q

What is the level of unconsciousness related to?

A

The state of unawareness

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7
Q

Definition of asleep

A

State of unconsciousness from which individual can be aroused by normal stimuli, light, touch, sound etc

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8
Q

Definition of a coma

A

State of unconsciousness from which individual cannot be aroused and does not respond to stimuli

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9
Q

What is involved in the induction of sleep?

A

Hypothalamus and its suprachiasmatic nuclei (SCN)

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10
Q

What does the SCN demonstrate?

A

Approx. 24 hr circadian rhythm

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11
Q

What would damage to the SCN cause?

A

Disruption to the sleep wake cycle

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12
Q

What does activity in the SCN cause?

A

Release of melatonin from the pineal gland - corresponding with the feeling of sleepiness

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13
Q

When is more melatonin produced?

A

Hours of darkness

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14
Q

What is required for wakefulness? Where is this produced?

A

Orexin/hypocretin

Released by hypothalamus

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15
Q

What does defective orexin signalling cause?

A

Narcolepsy

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16
Q

Pathology of narcolepsy

A

Hypocretin cells die

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17
Q

What does EEG stand for?

A

Electroencephalogram

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18
Q

What do EEGs show?

A

The electrical activity of the brain

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19
Q

How can EEG waves be analysed?

A

By

  • amplitude
  • frequency
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20
Q

What is the amplitude?

A

The size of the wave (ranges from 0-200Uv)

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21
Q

What is the frequency?

A

The number of waves per second (ranges from 1-50+)

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22
Q

In general, frequency of the waves increases with what?

A

Neuronal excitation

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23
Q

What are very long wavelengths associated with?

A

Deep surgical anaesthesia

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24
Q

When get more and more awake, what happens to the waves on EEG?

A

Get shorter and shorter

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25
Q

What waves on an EEG do epileptic seizures have?

A

Very short waves that are close together

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26
Q

4 main types of wave pattern seen on EEG

A

Alpha
Beta
Theta
Delta

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27
Q

Features of the EEG in the relaxed, awake state. What kind of waves are these?

A

High frequency
High amplitude waves
ALPHA WAVES

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28
Q

What waves are seen in the alert, awake state on the EEG?

A

B waves

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29
Q

Features of B waves

A

Higher frequency than A waves
Low amplitude
Asynchronous

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30
Q

Why do you get asynchronous waves with B waves?

A

Brain is doing so many things at once, and opposing polarities of the signals cancel each other out and do not get recorded on the EEG

31
Q

Features of theta waves

A

Low frequency

Can vary enormously in amplitude

32
Q

Who are theta waves common in?

A

Children
Emotional stress
Frustration
Sleep in both adults and children

33
Q

Features of delta waves

A

Very low frequency

High amplitude

34
Q

When do delta waves occur?

A

Deep sleep

35
Q

What are the stages of sleep?

A 
Stage 1
Stage 2
Stage 3
Stage 4
REM sleep
36
Q

What are stages 1 - 4 of sleep known as?

A

Slow wave sleep

37
Q

Describe stage 1 of sleep

A

Slow wave, non-REM, S-sleep
Slow eye movements
Light sleep
Easily roused

38
Q

What type of waves are seen in stage 1 of sleep?

A

High amplitude, low frequency theta waves

39
Q

Describe stage 2 of sleep

A

Eye movements stop
Frequency slows further but EEG shows bursts of rapid waves called “sleep spindles” (clusters of rhythmic waves approx. 12 - 14 Hz)

40
Q

Describe stage 3 of sleep

A

High amplitude very slow (2Hz) delta waves interspersed with short episodes of faster waves
Spindle activity declines
Very difficult to rouse

41
Q

What waves are seen in stage 4 of sleep?

A

Exclusively delta waves

42
Q

Describe stage 4 of sleep

A

Exclusively delta waves
Very difficult to rouse
Sleep walking/talking occur in these stages

43
Q

What is stage 4 of sleep known as?

A

Deep sleep

44
Q

What stages of sleep do sleep walking / talking occur?

A

3/4

45
Q

What is a main feature of REM sleep?

A

Rapid eye movements

46
Q

Another name for REM sleep

A

Paradoxical sleep

47
Q

What % of sleep is REM?

A

25%

48
Q

What does REM sleep look like on EEG?

A

Very similar to awake state but unconcious

49
Q

What stage of sleep do dreams occur?

A

REM sleep

50
Q

What is large amplitude of waves assosiated with?

A

Deepest sleep

51
Q

How long does the whole sleep cycle on average take?

A

90 mins

52
Q

As the cycle keeps going through the night, what happens?

A

REM sleep time increases

Time in deep sleep decreases

53
Q

Total sleep time through children and adolescence either increases or decreases

A

Decreases

54
Q

% of REM sleep in childhood and adolescence either increases or decreases

A

Decreases

55
Q

When is the total asleep time the longest in someones life? Why?

A

During development

When brain maturation and synaptic formation is occurring rapidly

56
Q

Physiological characteristics of deep, slow wave sleep

A

Deep sleep that occurs in the first hours of sleep
Most restful type of sleep
Associated with decreased vascular tone (and BP), resp and BMR (hence drop in temp)
Dreams may occur but rarely remembered

57
Q

How long does REM sleep last?

A

5 - 30 mins every 90 mins or so during a normal nights sleep, becoming more frequent as the night progresses and rest and recovery are restablished

58
Q

Physiological characteristics of REM sleep

A

Dreams occur mostly here
Eye muscles show bursts of rapid activity.
Profound inhibition of all other skeletal muscles due to inhibitory projections from pons to spinal cord. This prevents acting out dreams
HR/RR become irregular
Brain metabolism increases
Very difficult to arouse although can spontaenously wake in the morning from this stage, vividly recalling dreams

59
Q

What is REM sleep dependent on?

A

Cholinergic pathways within the reticular formation and their projections to the thalamus, hypothalamus and cortex

60
Q

Effects of anticholinesterases on REM sleep

A

Increase time in REM sleep

61
Q

What does REM sleep look like on EEG?

A

Mimics beta waves assosiated with highly alert awake state

62
Q

What happens during wakefullness in the sleep-wakefullness cycle?

A

Excitatory neurones in the ARAS are released from inhibition from sleep centres in reticular formation
Stimulate excitatory pathways both the CNS and PNS
Positive feedback from CNS and PNS sustains wakefullness in an individual for many hours

63
Q

What does ARAS stand for?

A

Ascending reticular activating system

64
Q

What happens when a person becomes sleepy?

A

Active cells become fatigued and excitatory signals fade
Inhibitory, peptide signals from the sleep centres likely to take over and rapidly dominate the weakening excitatory signals leading to rapid progression into the sleep state.

65
Q

Where are the sleep centres found?

A

In the reticular formation

66
Q

What happens to sleep deprived people?

A 
Impaired cognitive function 
Impairment of physical function 
Sluggishness
Irritability
Impairment of reaction time
67
Q

What does sleep support?

A 
Neuronal plasticity 
Learning and memory 
Cognition 
Clearance of waste products from CNS 
Conservation of whole body energy 
Immune function
68
Q

Examples of sleep disorders

A 
Insomnia 
Nightmares
Night terrors
Sommanbulism 
Narcolepsy
69
Q

Definition of insomnia

A

Chronic inability to obtain the necessary amount of quality of sleep to maintain adequate daytime behaviour

70
Q

What % of adults experience insomnia?

A

33%

71
Q

Types of insomnia

A

Chronic primary

Temporary secondary

72
Q

What is chronic primary insomnia?

A

There is usually an identifiable psychological or physical cause

73
Q

What is temporary, secondary insomnia?

A

Typically short lived Insomnia in reponse to

  • pain
  • bereavement
  • other crisis

Neuro Physiology (15 decks)

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