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Nervous System > Regolatory Systems: EEG, sleep and circadian rhythms > Flashcards

Regolatory Systems: EEG, sleep and circadian rhythms Flashcards

1
Q

what is sleep defined as?

A

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

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2
Q

what is coma defined as?

A

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

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3
Q

what do sleep deprived subjects demonstrate?

A

Impairment of cognitive function
Impairment of physical performance
Sluggishness
Irritability

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4
Q

what 6 physiological functions does sleep support?

A

Neuronal plasticity

Learning and memory

Cognition

Clearance of waste products from CNS

Conservation of whole body energy (although cerebral O2 consumption may actually increase, esp. during REM sleep)

Immune function (reason sleep increases when ill?)

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5
Q

what is the theory of sleep?

A

Sleep occurs due to active inhibitory processes that originate in the pons.

Evidence suggests the activity originates in the Reticular Formation of the brain stem, an area now known to be closely associated with controlling the state of consciousness.

It sends projections to the thalamus and higher cortical areas.

Arousal centres and sleep centres exist in the reticular formation and level of consciousness depends on balance in activity between the two.

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6
Q

what happens if there is destruction of the brainstem at level of the mid pons?

A

Destruction of the brainstem at the level of the mid-pons creates a brain that never sleeps.

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7
Q

Many molecules are believed to contribute to sleep name a few?

A

(Delta) Sleep inducing peptides (DSIP)
Adenosine
Melatonin
Serotonin

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8
Q

what is the function of DSIP?

A

DSIP peptide works by binding to receptors in the brain that are linked to sleep and relaxation. It helps increase the production of the chemical gamma-aminobutyric acid (GABA), which slows down brain activity, induces relaxation, and promotes deeper sleep

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9
Q

what is the function of adenosine in sleep?

A

adenosine is proposed to act as a homeostatic regulator of sleep and to be a link between the humoral and neural mechanisms of sleep-wake regulation. Both the adenosine A(1) receptor (A(1)R) and A(2A)R are involved in sleep induction. The A(2A)R plays a predominant role in the somnogenic effects of PGD(2).

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10
Q

What part of the hypothalamus does evidence suggest is involved in sleep?

A

Hypothalamus and its suprachiasmatic nuclei (SNC) are involved in induction of sleep

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11
Q

what does SCN activity demonstrate?

A

24hr circadian rhythm and controls release of melatonin from the pineal gland.

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12
Q

What are the inhibitory neurons in the SCN stimulated by?

A

Light and act to inhibit the pineal gland, darkness therefore corresponds with decreased activity in the SCN and increased melatonin release and feelings of sleepiness

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13
Q

what is melatonin produced by?

A

pineal gland

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14
Q

What is the circadian rhythm?

A

24 hour cycle in physiological processes of living beings

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15
Q

What is the circadian rhythm of melatonin release likely linked to the inhibition of?

A

orexin

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16
Q

What is orexin?

A

Orexin (aka hypocretin) is an excitatory neurotransmitter released from hypothalamus - required for wakefulness.

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17
Q

when are orexin neurons active?

A

Orexin neurons are active during the waking state

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18
Q

when do orexin neurons stop firing?

A

stop firing during sleep

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19
Q

what does defective orexin signalling cause?

A

Defective orexin signalling causes narcolepsy; individual will suddenly fall asleep, sometimes even when talking.

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20
Q

How does decreased activity of SCN impact melatonin release and orexin?

A

Decreased orexin

Increased melatonin

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21
Q

what is the relationship between serotonin and sleep?

A

Many neurons within the reticular formation are serotonergic; drugs that block serotonin formation inhibit sleep suggesting serotonin must be critical to sleep induction.

These effects may be related to melatonin production as serotonin is a precursor.

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22
Q

What does assessing the level of consciousness in an awake person involve?

A

Look at behaviour, general alertness, speech patterns, speech contents, reading, writing and calculating skills

Spell words backwards or count backwards

Record patterns of brain activity with electroencephlogram (EEG)

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23
Q

What is an electroencephalogram (EEG)?

A

Much of what we know about sleep come from recording patterns of brain activity using ElectroEncepheloGram (EEG).

EEG uses electrodes placed on the scalp to record activity of underlying neurons.

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24
Q

What can the waves produced by an EEG be analysed by?

A

Amplitude: the size of the wave (ranges from 0-200 µV)

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

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25
Q

What is the range of amplitude of brain waves on an EEG?

A

From 0-200uV

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26
Q

What is the range of frequencies of brain waves on an EEG?

A

ranges from 1-50+

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27
Q

How does frequency and amplitude of brain waves change with neuronal excitation?

A

Frequency - increased with neuronal excitation

Amplitude - decreases with neuronal excitation

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28
Q

What are the four main types of wave patterns seen on an EEG?

A

Alpha

Beta

Theta

Delta

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29
Q

What are EEG waves characterised by in relaxed, awake state?

A

High frequency

High amplitude

this is termed alpha waves

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30
Q

What are EEG waves characterised by when in alart, awake state?

A

Even higher frequency waves than alpha

Low amplitude asynchonous waves (due to brain doing many things at once so opposing polarities cancel each other out and do not get recorded on EEG)

this is termed beta waves

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31
Q

What is the amplitude and frequency like of alpha waves?

A

High amplitude

High frequency

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32
Q

What is the amplitude and frequency like of beta waves?

A

Low amplitude

Even higher frequency than alpha waves

33
Q

What is the amplitude and frequency like in theta waves?

A

Low frequency

Enourmous variation in amplitude

34
Q

Who are theta waves common in?

A

Children during times of emotional stress and frustration in adults

Also occur duing sleep in both adults and children

35
Q

What is the amplitude and frequency like of delta waves?

A

Very low frequency

High amplitude

36
Q

When do delta waves occur?

A

During deep sleep

37
Q

How many stages are there in the sleep cycle?

A

5

38
Q

explain the 5 stages of the sleep cycle?

A

Stage 1 - Slow wave, non-REM, S-sleep. Slow eye movements.
Light sleep very early in the sleep cycle. Easily roused. High amplitude, low frequency theta waves.

Stage 2 – Eye movements stop. Frequency slows further but EEG shows bursts of rapid waves called “sleep spindles” (clusters of rhythmic waves, ~12-14Hz)

Stage 3 – High amplitude, very slow (2Hz) delta waves interspersed with short episodes of faster waves, spindle activity declines.

Stage 4 – exclusively delta waves.

39
Q

which stages of sleep is it very difficult to rouse from?

A

Very difficult to rouse from stage 3 and 4 sleep. Known as Deep Sleep.

Sleep walking/talking occurs during these stages.

40
Q

what happens from stage 4 sleep before entering REM sleep?

A

From stage 4 sleep, move back up through stage 3 and stage 2 before entering REM sleep - during which there are rapid eye movements.

41
Q

when do dreams occur?

A

Dreams occur during REM sleep.

42
Q

what percentage of sleep is REM in adults?

A

25% of sleep is REM.

43
Q

how is the amplitude and frequency described in REM sleep?

A

Low amplitude, high frequency waves eerily similar to awake state

44
Q

How does the frequency of waves compare between REM sleep and stages 1 to 4?

A

Frequency is much greater in REM sleep, eerily similar to the awake stage

45
Q

What are some 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 therefore BP), respiratory and basal metabolic rate (hence drop in BT).

Hippocampus very active – creation of new memories?

Dreams may occur here but are rarely remembered

46
Q

Following initial slow wave sleep (stages 3 & 4), there is a gradual awakening towards Stage 1, but not like the initial Stage 1, instead REM sleep during which EEG waves are desynchronized, high frequency, low amplitude, very like the awake state hence aka. paradoxical sleep.

what is paradoxical sleep?

A

REM sleep

47
Q

Are waves synchonised in S-wave or REM sleep?

A

S wave

48
Q

How long does REM sleep last per 90 minutes?

A

5-30 minutes

49
Q

Does REM sleep become more or less frequent as the night progresses?

A

More frequent so rest and recovery is established

50
Q

In what stage of sleep do dreams mostly occur in?

A

mostly occur in REM sleep

51
Q

In what stage of sleep do the eyes move the fastest?

A

REM sleep, shows bursts of rapid activity

52
Q

What are the skeletal muscles like in REM sleep?

A

Profound inhibition of all other skeletal muscles due to inhibitory projections from pons to spinal cord. Prevents acting out of dreams.

53
Q

when is inhibition of all skeletal muscles lacking?

A

(This inhibition is lacking in REM Sleep Behavioural Disorder and people may act out their dreams, sometimes with disastrous consequences)

54
Q

What pathways is REM sleep dependent on?

A

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

55
Q

How do anticholinesterases change the amount of time spent in REM sleep?

A

Anticholinesterases increase time spent in REM sleep.

56
Q

How does the HR, RR, brain metabolism change in REM sleep?

A

HR/RR becomes irregular

Brain metabolism increased

57
Q

what do EEG pattern mimics?

A

beta waves associated with highly alert, awake state.

58
Q

whenever deprived of REM sleep what willl happen?

A

there is always a catch up when able to sleep again indicating that REM sleep must have an important physiological function.

59
Q

How does sleep time change through childhood and adolescence?

A

Decreases rapidly

60
Q

How does the percentage of REM sleep change through childhood and adolescence?

A

Declines:

80% in 10 week premature infant

50% at full term declining to a stable 25% in adulthood

may be absent by 80+

61
Q

In adulthood, what percentage of sleep is REM sleep?

A

25%

62
Q

What percentage of the population are affected by sleep disorders?

A

Up to 25%

63
Q

What are examples of sleep disorders?

A

Insomnia

Nightmares

Night terrors

Somnambulism (sleep walking)

Narcolepsy

64
Q

What is the medical term for sleep walking?

A

Somnambulism

65
Q

what is insomnia defined as?

A

chronic inability to obtain the necessary amount or quality of sleep to maintain adequate daytime behaviour”, very subjective, very common

66
Q

What are the different kinds of insomnia?

A

chronic, primary insomnia where there is usually no identifiable psychological or physical cause

temporary, secondary insomnia in response to pain, bereavement or other crisis. Usually short lived.

67
Q

What drugs are used to treat insomnia?

A

Barbiturates (but depress REM sleep and delta sleep)

Benzodiazepines (less effect on REM sleep but addictive)

68
Q

What is the preferred approach to treat insomnia?

A

Change in behaviour to support induction of sleep, not drugs as have many side effects

69
Q

In what stage of sleep are nightmares usually experienced?

A

REM sleep, typically occurring quite far on through the night.

Waking will stop the nightmare and the individual will have a clear recollection of the “dream”.

70
Q

In what stage of sleep do night terrors occur in?

A

Deep, delta sleep

71
Q

How does the timing of nightmares and night terrors compare?

A

occur in deep, delta sleep

typically occurring early in the night

72
Q

Who are night terrors common in?

A

Children aged 3 to 8, where they trash and scream and may sit or stand up with their eyes open but are not properly awake and fail to recognise their parents

73
Q

how do children react to a night terror?

A

Children thrash and scream and may sit or stand up with their eyes open but are not properly awake and often fail to recognise their parents. The child does not remember the episode on waking the following morning.

74
Q

During what stage of sleep does somnambulism normally occur?

A

occurs exclusively in non-REM sleep

75
Q

How is somnambulism most common in?

A

more common in children and young adults, probably due to the decline in Stage 4 sleep with age.

76
Q

how do sleepwalkers appear?

A

eyes open, see and will avoid objects, carry out reasonably complex task such as preparing food and will often obey instructions but have no recall of the episode when woken.

77
Q

What kind of sleep do people with narcolepsy enter directly into?

A

Enter directly into REM sleep with little warning

78
Q

What is narcolepsy linked to the dysfunction of?

A

Dysfunctional orexin release from the hypothalamus

79
Q
A

Nervous System (40 decks)

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