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The Nervous System: Physiology > EEG, Sleep and Circadian Rhythms > Flashcards

EEG, Sleep and Circadian Rhythms Flashcards

1
Q

Where does the process of sleep originate from

A

The reticular formation of the brain stem

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2
Q

What is the function of the reticular formation

A

An area that controls the state of consciousness

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3
Q

If brain stem was destroyed at the level of the midpons what would occur

A

Brain never sleeps

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4
Q

How does the reticular formation promote sleep

A

Inhibitory impulses to thalamus and higher cortical areas to dampen down activity in cortex and put in state of unawareness

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5
Q

What are many neurones within the reticular formation,

A

Serotonergic

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6
Q

What is serotonergic

A

a nerve ending that releases and is stimulated by serotonin

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7
Q

What neurotransmitter is critical for sleep induction

A

Serotonin

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8
Q

What is serotonin a precursor of

A

Melatonin

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9
Q

What induces natural sleep

A

Serotonin

Melatonin

Sleep inducing peptides (isolated from CSF of a different sleep deprived animal)

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10
Q

How is the hypothalamus involved in the induction of sleep

A

Due to suprachiasmatic nuclei lying just above the optic chiasma creating a 24hr circadian rhythm

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11
Q

What causes the the electrical stimulation of the SCN that promotes sleep

A

Darkness - when light stops hitting the back of the retina

nerve fibres in the optic nerve pass to SCN

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12
Q

What does the electrical stimulation of the SCN stimulate

A

The release of melatonin from the pineal gland - which corresponds to the sleepiness in humans

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13
Q

What neurotransmitter does the hypothalamus release thats required for wakefulness

A

The excretory neurotransmitter - orexin (aka hypocretin)

Active during wake state and stop firing during sleep

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14
Q

What does defective orexin signalling cause

A

Narcolepsy - suddenly fall asleep

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15
Q

How is the wakefulness cycle sustained for many hours

A

Excitatory neurons in the Ascending Reticular Activating System (ARAS), are released from Sleep Centres in Reticular Formation stimulating excretory pathways in both CNS and PNS creating a positive feedback loop

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16
Q

What occurs for sleep cycle to occur from wakefulness cycle

A

Active cells become fatigues causing excretory signals to fade, so inhibitory peptide signals from sleep centres in the reticular formation dominate weakened excretory signal and lead to progression into sleep state

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17
Q

How is sleep cycle overthrown from wakeful cycle

A

Inhibitory cells fatigue and excretory cells are reinvigorated

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18
Q

What is the two methods to asses level of consciousness in an awake person

A

Look at their behaviour/alertness/skills /ability

EEG - record patterns of brain activity

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19
Q

What occurs in an EEG

A

Electrodes placed on scalp to record activity of underlying neurones

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20
Q

What are brain waves from EEG analysed by

A

Amplitude - size of the wave

Frequency - number of waves per second

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21
Q

Frequency is the most important factor of brain activity so what is the affect of Increased neuronal excitation on it

A

Frequency increased with neuronal excitation

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22
Q

What are the four main types of brain waves patterns recored on an EEG

A

Alpha

Beta

Theta

Delta

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23
Q

What causes the various characteristic of wave pattern

A

Different states of consciousness

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24
Q

What is the characteristics of alpha waves

A

High frequency and high amplitude

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25
What is the characteristic of beta waves
The highest frequency and low amplitude
26
What waves are involved in a relaxed awake state
Alpha waves
27
What waves are a involved in alert wake state
Beta waves
28
Why do you have a higher amplitude of waves in a relaxed state
Not music info coming into the brain so waves are sync with each other, therefore add together give a larger wave
29
Why do you have a high frequency and low amplitude in a alert state
Alert state means you have lots of info coming into the brain giving a greater frequency and this means waves become asynchronous and cancel each other out creating a lower amplitude
30
What is theta waves characterised by
Low frequency and varies enormously in amplitude
31
When is theta waves common
Children, Times of emotional stress and frustration in adults
32
What are delta waves characterised by
Low frequency but high amplitude
33
What waves are seen in sleep of both adults and children
Theta waves
34
What waves are seen in deep sleep
Delta waves
35
How many stages occur in a sleep cycle
5
36
What occurs in stage 1 of sleep cycle
Slow wave, non-REM, S-sleep. Slow eye movements. Light sleep. Easily roused. High amplitude, low frequency theta waves.
37
What occurs in stage 2 of sleep cycle
Eye movements stop. Frequency slows further but EEG shows bursts of rapid waves called “sleep spindles” (clusters of rhythmic waves, ~12-14Hz)
38
What occurs in stage 3 sleep cycle
High amplitude, very slow (2Hz) delta waves interspersed with short episodes of faster waves, spindle activity declines.
39
What occurs during stage 4 of sleep cycle
exclusively delta waves
40
What occurs during stage 5 of sleep cycle
REM sleep - during which there are rapid eye movements (paradoxical sleep)
41
What occurs during REM sleep
Dreams | - if spontaneously awaken in the morning during this stage of sleep will vividly recall dreams
42
What percentage of sleep is REM
25% of sleep is REM
43
When does deep sleep occur - become difficult to rouse
From stage 3 -4
44
What is stage 1-4 classified as
Slow wave sleep
45
How is REM sleep characterised
Fast waves, similar to those of awake state
46
When the amplitude is the highest in sleep what does this indicate
deep sleep
47
What is the 4 physiological characteristic 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 therefore BP), respiratory and basal metabolic rate (hence drop in BT) Dreams may occur but are rarely remembered
48
Why is the term paradoxical sleep used
Due to REM sleep occurring which is very similar to awake state as mimics the beta waves
49
How frequent and long does REM sleep last
Lasts 5-30mins every 90mins or so during a normal nights sleep, becomes more frequent as night progresses
50
How does inhibition of all other skeletal muscles (minus eye muscle) occur in REM sleep
Due to inhibitory projections from pons to spinal cord
51
What pathway is REM sleep dependent on
Cholingeric pathway within the reticular formation
52
Where does the REM pathways projections go
Thalamus Hypothlamus Cortex
53
What is the affect of anticholinesterases
Increase time spent in REM sleep
54
What is REMs affect on Heart /respiration rate and brain metabolism
HR/RR become irregular Brain metabolism increases
55
What occurs if you are deprived of REM sleep and what does this show
there is always a catch up when able to sleep again indicating that REM sleep must have an important physiological function
56
What is 4 features are demonstrated in sleep deprived subjects
Impairment of cognitive function Impairment of physical performance Sluggishness Irritability
57
What can occur with severe sleep deprivation
Psychosis Death
58
What important functions does sleep support
Neuronal plasticity Learning and memory Cognition Clearance of waste products from CNS Conservation of whole body energy Immune function (when ill, increase sleep)
59
What are sleep changes seen over a lifetime
Total sleep time decrease rapidly through childhood and adolescence Percentage of REM sleep declines
60
What is the percentage of REM sleep over lifetime
80% in 10 week premature infant, 50% at full term declining to a stable 25% in adulthood Can be absent by 80+years
61
Why is total time asleep greatest during development
Brain maturation and synaptic formation is occurring rapidly
62
Name 5 sleep disorders
Insomnia Night mares Night terrors Somnambulism (sleep-walking) Narcolepsy
63
Define insomnia
a “chronic inability to obtain the necessary amount or quality of sleep to maintain adequate daytime behaviour
64
What is the two types of insomnia
chronic, primary insomnia temporary, secondary insomnia
65
In chronic insomnia there is no identifiable cause, but what is the potential cause of temporary insomnia
Pain Bereavement Or other crisis
66
What occurs during a nightmare
Nightmares have a strong visual component and are seen during 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"
67
When do night terrors occur
Deep, delta sleep common in children 3-8 years Occurring early in the night
68
What occurs in night terrors
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.
69
When does Somnambulism (Sleep-walking) occur
Stage 4 deep sleep | non REM sleep
70
Why is sleep walking more common in children and young adults
due to the decline in Stage 4 sleep with age
71
What occurs in Somnambulism (Sleep-walking)
Somnambulists walk with their eyes open, can see and will avoid objects, can carry out reasonably complex task such as prepare food and will often obey instructions but have no recall of the episode when woken
72
What occurs in narcolepsy
Patients enter directly into REM sleep with little warning. Symptoms could be interpreted as intrusion of REM sleep characteristics onto the waking state
73
How is circadian rhythm lost if SCN is destroyed
due to the loss of melatonin signalling and disruption of orexin signalling in the hypothalamus
74
How can blind people form a circadian rhythm from the SCN as don't have eternal cues such as light and dark cycles
wakefulness normally being stimulated in the morning, when orexin level rises and sleep occurring at night, when orexin levels fall

The Nervous System: Physiology (15 decks)

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