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Neurology physiology > EEG, Sleep And Circadian Rhythms > Flashcards

EEG, Sleep And Circadian Rhythms Flashcards

1
Q

Sleep occurs due to inhibitory processes that originate in the …..?

A

Pons

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2
Q

Destruction of what part part of the brain will cause a brain that never sleeps?

A

Destruction of the brainstem at the level of the mid-pons

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3
Q

What is the function of the reticular formation nuclei?

A

Responsible for state of consciousness

They are also responsible for the feedforward mechanism for maintaining posture when we carry out voluntary movements

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4
Q

Many neurones within the reticular formation are term as?

A

Serotogenic

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5
Q

Why are many neurones within the reticular formation termed as serotogenic?

A

The reticular formation of the brain stem contains neurones which are responsible for controlling state of consciousness
Serotonin is a precursor of melatonin which is important in sleep induction

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6
Q

Why is serotonin levels and depression linked?

A

In depression, insomnia is common

The insomnia is linked with depression because they both show decreased levels of serotonin

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7
Q

Where are suprachiasmatic nuclei found and what are their purpose?

A

Found in the hypothalamus

Important in sleep induction

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8
Q

Does electrical stimulation of suprachiasmatic nuclei cause sleep induction or sleep suppression?

A

Sleep induction

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9
Q

What causes release of melatonin and where is it released from?

A

Activity in the suprachiasmatic nuclei stimulate release of melatonin from the pineal gland
(Corresponds to the feeling of sleepiness)

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10
Q

What is a precursor of melatonin?

A

Serotonin

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11
Q

What is released from the hypothalmaus which stimulates wakefulness?

A

Orexin / hypocretin

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12
Q

Where are excitatory neurones And neurotransmitters found which cause wakefulness?

A

Neurones - ascending reticular activity system (ARAS) part of the reticular formation in the brainstem
Neurotransmitter - orexin released from the hypothalamus

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13
Q

How do you assess consciousness in an awake person?

A

Look at their behaveiours, general alertness, speech patterns & content, reading, writing , calculating skills
Record pattern of brain activity using EEG

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14
Q

What does EEG stand for?

A

Electroencephalogram

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15
Q

How does the EEG work?

A

Uses electrodes placed on the scalp to record activity of underlying neurones

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16
Q

As the conciousness/awakefulness of a person increases from unconscious, how does the frequency and amplitude of waves change?

A

Unconscious - really alert awake

Frequency increases
Amplitude decreases

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17
Q

What are the 4 main types of wave patterns on an EEG? And what do they correspond to in regards to conciousness?

A

Alpha - relaxed awake state
Beta - alert awake state
Theta - occur during sleep in children and adults, also occur during stress, frustration etc
Delta - deep sleep

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18
Q

Describe delta waves.

A

Very Low frequency, high amplitude

Occur in deep sleep

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19
Q

Describe alpha waves compared to beta waves.

A

alpha = Relaxed awake
High frequency and high amplitude
Beta = alert awake
Higher frequency but lower amplitude

20
Q

Why does amplitude on an EEG decrease with increasing brain activity?

A

Activity is asynchronised as the brain is doing so many things at once and the opposing polarities of signals cancel out each other so don’t record on EEG

21
Q

What waves are present in the sleep cycle stage 1?

A

Theta waves - low frequency, high amplitude

22
Q

What is found in stage 2 of the sleep cycle?

A

Eye movements stop
Frequency slows further
Bursts of rapid waves called sleep spindles

23
Q

In what stage of the sleep cycle is delta waves found?

A

Stage 3, interspersed with short episodes of fast waves

Stage 4 - exclusively delta waves

24
Q

What stages of the sleep cycle does sleep walking/talking occur and what type of waves are found at these stages?

A

Stage 3 (delta with short episodes of faster waves/ spindles) and stage 4 (delta waves)

25
Q

What type of sleep is REM?

A

Paradoxical

26
Q

What are the waves like in REM sleep?

A

Very fast - similar to that of an awake person

27
Q

What percentage of sleep is REM?

A

25%

28
Q

What type of sleep occurs in the early hours and in the later hours/early morning?

A

Early night - most deep sleep occurs

Late hours/early morning - most REM sleep occurs

29
Q

What is the duration/cycle of REM sleep?

A

Lasts 5-30 mins every 90 mins

Becomes more freuqnt as the night goes on when rest is established

30
Q

What prevents the acting out of dreams?

A

During REM sleep there is rapid eye muscle activity.

But there is inhibition of all other skeletal muscles due to profound inhibitory projections from pons to spinal cord

31
Q

What is REM sleep dependant on?

A

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

32
Q

What waves are found in REM sleep?

A

Beta waves - awake alert state

33
Q

Sleep deprivation can cause…

A

Impairement of cognitive function
Impairement of physical performance
Sluggishness
Irritability

34
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
35
Q

How does sleep change over a life time?

A

Percentage of REM sleep declines as we age
80% in 10 week premature infant, 50% at full term
25% in adulthood
May be absent by 80+ yrs
Total sleep is greatest when brain maturation and synaptic formation is occurring rapidly

36
Q

What is the clinical significance of REM sleep being absent by 80+ yrs?

A

This may suggest that older people may find it harder to consolidate memory due to lack of REM sleep

37
Q

What stage of the sleep cycle is nightmares seen?

A

REM sleep

38
Q

During night terrors, what type of wave is found on EEG?

A

Delta waves - occurs in deep sleep

39
Q

What i somnambulism and when does it occur?

A

Sleep walking

Occurs during non-REM sleep

40
Q

What is narcolepsy?

A

Patients enter directly into REM sleep without warning

I.e. occur through the day without feeling tired

41
Q

What is the treatment for insomnia?

A

Used to use benzodiazepines- less side effects on REM sleep but are addictive and can cause problems with withdrawal i.e. falling asleep
Hypnotic sleeping drugs - come with risk of dementia
Best treatment - lifestyle/behaviour changes

42
Q

Where is our circadian rhythm directed from? (Master clock)

A

Suprachiasmatic nucleus (SCN) of the hypothalamus

43
Q

If orexin levels fall, does this cause sleepiness or wakefulness?

A

Sleepiness

44
Q

If serotonin levels rise does this cause sleepiness or wakefulness?

A

Sleepiness

45
Q

What is responsible for our sleep clock / circadian rhythm?

A

Suprachiasmatic nucleus found in the hypothalamus

Neurology physiology (7 decks)

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