Neuro Physiology > EEG, Sleep and Circadian Rhythms > Flashcards

EEG, Sleep and Circadian Rhythms Flashcards

(73 cards)

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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
What waves on an EEG do epileptic seizures have?
Very short waves that are close together
26
4 main types of wave pattern seen on EEG
Alpha Beta Theta Delta
27
Features of the EEG in the relaxed, awake state. What kind of waves are these?
High frequency High amplitude waves ALPHA WAVES
28
What waves are seen in the alert, awake state on the EEG?
B waves
29
Features of B waves
Higher frequency than A waves Low amplitude Asynchronous
30
Why do you get asynchronous waves with B waves?
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
Features of theta waves
Low frequency | Can vary enormously in amplitude
32
Who are theta waves common in?
Children Emotional stress Frustration Sleep in both adults and children
33
Features of delta waves
Very low frequency | High amplitude
34
When do delta waves occur?
Deep sleep
35
What are the stages of sleep?
``` Stage 1 Stage 2 Stage 3 Stage 4 REM sleep ```
36
What are stages 1 - 4 of sleep known as?
Slow wave sleep
37
Describe stage 1 of sleep
Slow wave, non-REM, S-sleep Slow eye movements Light sleep Easily roused
38
What type of waves are seen in stage 1 of sleep?
High amplitude, low frequency theta waves
39
Describe stage 2 of sleep
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
Describe stage 3 of sleep
High amplitude very slow (2Hz) delta waves interspersed with short episodes of faster waves Spindle activity declines Very difficult to rouse
41
What waves are seen in stage 4 of sleep?
Exclusively delta waves
42
Describe stage 4 of sleep
Exclusively delta waves Very difficult to rouse Sleep walking/talking occur in these stages
43
What is stage 4 of sleep known as?
Deep sleep
44
What stages of sleep do sleep walking / talking occur?
3/4
45
What is a main feature of REM sleep?
Rapid eye movements
46
Another name for REM sleep
Paradoxical sleep
47
What % of sleep is REM?
25%
48
What does REM sleep look like on EEG?
Very similar to awake state but unconcious
49
What stage of sleep do dreams occur?
REM sleep
50
What is large amplitude of waves assosiated with?
Deepest sleep
51
How long does the whole sleep cycle on average take?
90 mins
52
As the cycle keeps going through the night, what happens?
REM sleep time increases | Time in deep sleep decreases
53
Total sleep time through children and adolescence either increases or decreases
Decreases
54
% of REM sleep in childhood and adolescence either increases or decreases
Decreases
55
When is the total asleep time the longest in someones life? Why?
During development | When brain maturation and synaptic formation is occurring rapidly
56
Physiological characteristics of deep, slow wave sleep
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
How long does REM sleep last?
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
Physiological characteristics of REM sleep
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
What is REM sleep dependent on?
Cholinergic pathways within the reticular formation and their projections to the thalamus, hypothalamus and cortex
60
Effects of anticholinesterases on REM sleep
Increase time in REM sleep
61
What does REM sleep look like on EEG?
Mimics beta waves assosiated with highly alert awake state
62
What happens during wakefullness in the sleep-wakefullness cycle?
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
What does ARAS stand for?
Ascending reticular activating system
64
What happens when a person becomes sleepy?
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
Where are the sleep centres found?
In the reticular formation
66
What happens to sleep deprived people?
``` Impaired cognitive function Impairment of physical function Sluggishness Irritability Impairment of reaction time ```
67
What does sleep support?
``` Neuronal plasticity Learning and memory Cognition Clearance of waste products from CNS Conservation of whole body energy Immune function ```
68
Examples of sleep disorders
``` Insomnia Nightmares Night terrors Sommanbulism Narcolepsy ```
69
Definition of insomnia
Chronic inability to obtain the necessary amount of quality of sleep to maintain adequate daytime behaviour
70
What % of adults experience insomnia?
33%
71
Types of insomnia
Chronic primary | Temporary secondary
72
What is chronic primary insomnia?
There is usually an identifiable psychological or physical cause
73
What is temporary, secondary insomnia?
Typically short lived Insomnia in reponse to - pain - bereavement - other crisis

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