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Year 2 - Nervous > EEG, sleep & circadian rhythms > Flashcards

EEG, sleep & circadian rhythms Flashcards

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1
Q

Define sleep

A

State of unconsciousness from which you can be aroused by stimuli (light, touch, sound)

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2
Q

Sleep occurs due to active inhibitory processes that originate where in the brain

A

Pons

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3
Q

Something below the level of the … must be actively sending … to the cortex

Evidence suggests this activity originates in the … of the brainstem

A

Mid-pons

Inhibitory impulses

Reticular formation

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4
Q

Many neurons within the reticular formation are…

A

Serotonergic - produce serotonin

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5
Q

Drugs that block serotonin formation inhibit or induce

A

Inhibit, so serotonin is critical to sleep induction

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6
Q

Serotonin is a precursor of what chemical

A

Melatonin

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7
Q

Melatonin levels in the blood increase at morning or night

A

Night

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8
Q

By the morning, melatonin levels have rised or dropped

A

Dropped completely

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9
Q

What is the circadian rhythm

A

24-hour internal clock that is running in the background of your brain and cycles between sleepiness and alertness at regular intervals

It’s also known as your sleep/wake cycle

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10
Q

What part of the brain controls the circadian rhythm

A

Suprachiasmatic nucleus (SCN) in the hypothalamus

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11
Q

Suprachiasmatic nucleus (SCN) in the hypothalamus that controls the circadian rhythm sits above what structure in the brain

A

Optic chasm

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12
Q

The circadian rhythm is entrained by external cues such as

A

Light/dark cycles but is not the entrainment as blind people have circadian rhythms too

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13
Q

Activity in the SCN stimulates release of what chemical

A

Melatonin

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14
Q

What gland produces melatonin

A

Pineal gland

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15
Q

The hypothalamus releases what excitatory neurotransmitter that’s required for wakefulness (2 different names)

A

Orexin (aka hypocretin)

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16
Q

Defective orexin signalling can cause what condition + describe a bit about it

A

Narcolepsy - suddenly fall asleep, enter directly into REM sleep with little warning

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17
Q

If the SCN is destroyed, then the circadian rhythm of sleep is lost, explain the likely reason for this

A

Loss of melatonin signalling and disruption of orexin signalling in the hypothalamus, (wakefulness normally being stimulated in the morning, when orexin level rises; sleep occurring at night when orexin levels fall).

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18
Q

Are orexin levels high in the morning or night

A

Morning

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19
Q

Name the 2 centres in the reticular formation

A

arousal centre + sleep centre

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20
Q

Where is the reticular formation (regulates sleep and consciousness) located

A

Brainstem

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21
Q

How do we have a self-sustaining cycle of wakefulness for many hours

A

Excitatory neurons in the Ascending Reticular Activating System (ARAS) stimulate excitatory pathways in the CNS & PNS
–> These further excitatory pathways then create a positive feedback cycle from the CNS and PNS back to the ARAS, boosting the ARAS

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22
Q

Towards the end of the day, excitatory neurons and signals become fatigued and fade. At this point, what takes over

A

Inhibitory peptide signals from the Sleep Centres in the Reticular Formation

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23
Q

What investigation can assess level of consciousness in an awake person

A

EEG (Electroencephalogram)

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24
Q

What does EEG record

A

wave patterns that reflect the electrical activity of the brain

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25
What 2 things are interpreted from the wave patterns reflecting electrical activity on an EEG reading + describe what each of these are
Amplitude (wavelength): the size of the wave (ranges from 0-200 µV) Frequency: number of waves per second (ranges from 1-50+)
26
In increasing consciousness, - frequency increases or decreases - amplitude increases or decreases
frequency increases | amplitude decreases
27
In decreasing consciousness, - frequency increases or decreases - amplitude increases or decreases
frequency decreases | amplitude increases
28
Describe the frequency and amplitude of an EEG of someone - under anaesthesia - in a seizure
Under anaesthesia: High amplitude Low frequency In a seizure: High frequency Low amplitude
29
4 main types of wave pattern of an EEG
1) Alpha 2) Beta 3) Theta 4) Delta
30
In awake, relaxed state, what type of wave is seen on an EEG
Alpha waves
31
When there’s less stimuli to the brain, neurons firing synchronously...
Summate and so increase their amplitude
32
Describe the amplitude and frequency of an EEG of someone in the - awake, relaxed state - awake, alert state
Awake & relaxed: High frequency High amplitude Awake & alert: Even higher frequency Low amplitude
33
In awake, alert state, what type of wave is seen on an EEG
Beta waves
34
Why is the amplitude low but the frequency high on an EEG of someone in the awake, ALERT state
So much electrical activity going on in the alert state that neurons fire asynchronously (out of sequence with each other) because so many stimuli --> desynchronised waves cancel each other out and don't get recorded on EEG
35
Are theta waves high or low frequency waves
Low
36
When do you see theta waves on an EEG (3)
Common in children, and during times of emotional stress and frustration in adults Also occur during sleep
37
Describe the frequency and amplitude of delta waves
Very low frequency | High amplitude
38
When do you see delta waves on an EEG
Deep sleep
39
How many stages of sleep
5
40
Describe stage 1 sleep (S-sleep) - eye movements - light/deep - amplitude & frequency & wave type
Slow eye movements. Light sleep so easily aroused. High amplitude, low frequency theta waves
41
Describe stage 2 sleep - eye movements - frequency of waves (2)
Eye movements stop Frequency slows overall - but there's bursts of rapid waves called sleep spindles (clusters of high frequency waves)
42
Describe stage 3 sleep - amplitude & frequency of waves - wave type - light/deep sleep
High amplitude, very slow (2Hz) delta waves interspersed with short episodes of faster waves Spindle activity (bursts of high frequency waves) declines DEEP SLEEP
43
Describe stage 4 sleep - wave type - amplitude & frequency of waves - light/deep sleep
delta waves - high amplitude, low frequency Deep sleep
44
Describe stage 5 sleep - eye movements - frequency & amplitude
REM sleep - rapid eye movements Fast, high frequency waves, low amplitude like those of the awake state
45
What percentage of sleep is REM sleep
25%
46
Slow wave sleep = what stages of sleep
Stages 1-4
47
How long do the 5 stages take before the cycle repeats itself again
90 mins
48
Time spent in REM sleep increases or decreases as the sleep cycle repeats Time spent in deep sleep increases or decreases as the sleep cycle repeats
Increases Decreases
49
Most restful sleep is in what stage of sleep
4
50
What stage is S-wave sleep (Deep slow wave sleep)
4
51
Physiological characteristics of stage 4 sleep (3)
Decreased vascular tone (and therefore BP), respiratory and basal metabolic rate
52
How long does REM sleep last
5-30 mins
53
Why do only the eye muscles move during REM sleep but no other skeletal muscles
due to inhibitory projections from pons to spinal cord
54
REM sleep is dependent on what neurotransmittory pathway
Cholinergic pathways | - anticholinesterases increase time spent in REM sleep because they boost ACh release
55
What happens to HR, RR and brain metabolism in REM sleep (D-sleep)
Increases
56
What wave type does the EEG pattern during REM sleep mimic
Beta waves associated with alert, awake state
57
Is it easy or hard to arouse someone from REM sleep
Hard
58
Sleep deprived people demonstrate what characteristics (4)
1. Impairment of cognitive function (detected in early hours of sleep deprivation) 2. Impairment of physical performance (detected in early hours of sleep deprivation) 3. Sluggishness 4. Irritability
59
Sleep supports what physiological functions (5)
1. Neuronal plasticity (needed for learning + memory) 2. Learning and memory 3. Cognition 4. Clearance of waste products from CNS (rejuvenates neurons) 5. Conservation of whole body energy
60
Percentage of sleep that is REM sleep in full term babies
50%
61
Define insomnia
chronic inability to obtain the necessary amount or quality of sleep to maintain adequate daytime behaviour
62
2 types of insomnia
a) chronic, primary insomnia where there is usually no identifiable psychological or physical cause b) temporary, secondary insomnia in response to pain, bereavement or other crisis.
63
What drug used to be used to treat insomnia but not anymore + why (consequences)
Barbiturates Chronic use increases time taken to fall asleep, decreases time spent in REM and stage 3 and 4 sleep, and increases no. of times awake during night Dose required to treat insomnia too close to toxic dose
64
Preferred insomnia treatment instead of barbiturates and benzodiazepines
Lifestyle habits that induce sleep
65
What stage of the sleep cycle do night terrors occur
Deep, delta sleep (stage 4)
66
Nightmares v night terrors
Nightmares are during REM sleep Night terrors during stage 4 deep sleep, don't really remember night terrors
67
What is somnambulism + when does it occur
Sleep walking Mainly in stage 4 sleep, never in REM No recollection of it when waking up

Year 2 - Nervous (39 decks)

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