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NSB > The Physiology of Sleep > Flashcards

The Physiology of Sleep Flashcards

1
Q

Define Sleep

A

a natural period state of rest for the mind and body, in which the eyes usually close and consciousness in completely or partially lost, so that there is a decrease in bodily movement and responsiveness to external stimuli

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2
Q

Sleep Deprivation can lead to:

A
  • grumpiness
  • grogginess
  • irritability
  • forgetfulness
  • language, memory, planning and
    sense of time are severely affected
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3
Q

How do we measure sleep?

A
  • questionnaire
  • physiological measurements EEG
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4
Q

Analysis of Sleep: Questionnaire:

A
  • eg do you feel your sleep is not
    refreshing or restful
  • results can be limiting due to
    increased error due to bias
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5
Q

Analysis of Sleep: Physiological Measurements:

A
  • more complex approach
  • eg brain waves, neurochemicals,
    sleep models, pharmacology
  • results are limited by methods
    used, mostly free from bias and
    are reproducible
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6
Q

EEG stands for

A

Electroencephalography

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7
Q

EEG: Method:

A

involves the recording of a gross average of electrical potentials of the cells and fibers in the brain areas closes to each electrode attached to the scalp

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8
Q

EEG: Basic Principle:

A
  • neurons generate electrical action
    potentials
  • the firing of many neurons creates
    a large electrical field in particular
    brain regions
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9
Q

Generation of small fields in pyramidal cells:

A

insert diagram

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10
Q

What are the 2 basic requirements for signal detection?

A
  • a whole population o fneurons
    must be active in synchonicity to
    generate a large enough electrical
    field at the level of the scalp
  • this population of neurons must
    be aligned in a parallel orientation
    so that they summate rather than
    cancel out
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11
Q

The amplitude of EEG signals depends upon:

A
  • the synchronous activity of
    underlying neurons
  • number of active cells, total
    amount of excitation, timing of
    activity are key contributors
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12
Q

What type of cells generate synchronous rhythmns?

A

Thalamic cells have a set of voltage-gated ion channels that allow each cell to generate rhythmic, self-sustaining discharge patters even in the absence of external inputs

the rhythmic activity of each thalamic pacemaker neuron then becomes synchronised with many other thalamic cells through cellular and chemical communication

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13
Q

Function of Brain Rhythms?

A
  • sensory input travels to thalamus,
    then directed to functional area of
    cortex
  • meaningless by-product of
    feedback circuits and connections
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14
Q

EEG Recordings:

A
  • electrical potentials are recorded
    from either the entire skull surface
    or from specific points
  • electrical potentials are recorded
    as traces
  • increased, synchronised activity is
    displayed as a larger amplitude
    than the baseline recording
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15
Q

Interpreting Sleep Through EEGs:

A
  • EEG recorded whilst asleep
  • observes monitored behavioural
    changes during sleep
  • traces obtained were analysed
    from amplitude and frequency of
    wave patterns
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16
Q

EEG:
- flat line
- peak
- trough

A

Flat line = half the neurons recorded are firing, half are inhibiting

Peak = all are firing in that area

Trough = none are firing in that area

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17
Q

Whilst sleeping, heart rate, breathing rate and brain activity

A

decrease

18
Q

Major behavioural changes whilst sleeping:

A
  • lack of gross movement (large
    amounts of muscle movement)
  • presence of Rapid Eye Movement
    (REM) cycles throughout a period
    of sleep
19
Q

Correlating EEG with Behaviour:

All are different stages:

A

insert slide

20
Q

EEG:

A

insert figure

21
Q

How many stages in sleep?

A
  • 4 stages non-REM sleep (N1,2,3)
  • 1 stage REM sleep
22
Q

Sleep: N1:

A
  • non-REM sleep
  • dominated by irregular, jagged,
    low voltage waves
  • brain activity is high but will start
    to decline
23
Q

Sleep: N2:

A
  • non-REM sleep
  • sleep spindles
  • K-complexes
24
Q

Sleep: N2: Sleep Spindles:

A
  • 12-14Hz burst for at least 500msec
  • generated by oscillating
    interactions between cells in the
    thalamus and the cortex
25
Q

Sleep N2: K-Complexes:

A
  • sharp, high amplitude positive
    wave
  • followed by a smaller, slow,
    negative wave
  • occurs randomly and in response
    to auditory stimuli
26
Q

Sleep: N3:

A
  • Non-REM
  • delta waves
27
Q

Sleep: N3: Delta Waves:

A
  • slow, large amplitude waves
  • neural activity is highly
    synchronised
28
Q

Sleep: Stage 4 N3:

A
  • Non-REM
  • increased delta wave activity
  • stage 3 and 4 are known together
    as slow-wave sleep (SWS)
  • sleepwalking, nightmares, bed
    wetting can occur at this stage of
    sleep
29
Q

Sleep: REM Stage (5):

A
  • rapid eye movement
  • irregular, low voltage fast waves,
    similar to those in stage 1 of non-
    REM sleep
  • increased brain activity, may be
    associated with a state of
    dreaming
30
Q

Describe the waves on EEG when awake with eyes open.

A

low amplitude = no synchronicity, all neurons are doing different things

beta waves in all stages

high frequency low amplitude = brain is active

31
Q

Describe the waves on EEG when awake with eyes closed.

A

high frequency similar to awake with eyes open = brain is active

higher amplitude than awake with eyes open = more synchronicity (visual neurons)

32
Q

In Non-REM sleep, neurons become more

A

synchronised (larger amplitude, lower frequency)

33
Q

In REM sleep, neurons are

A

synchronised but very active as dreaming

34
Q

Newborn babies wake every 1.5 hours because

A

struggle with transition from light sleep in non-REM to deep REM sleep

35
Q

How long does the entire sleep cycle last?

A
  • 90-120 minutes
  • first cycle starts at stage 1
  • subsequent cycles will start at
    stage 2 and continue through to
    REM sleep every 90 - 110 minutes
36
Q

REM Sleep: Physiological Changes:

A
  • postural muscles become more
    relaxed = deep REM sleep
  • heart rate, bp, rr are more variable
    than other stages of sleep
  • increased blood supply to
    reproductive organs
37
Q

Influences of Benzodiazepines on Sleep:

A
  • bind to gaba a receptors
  • Cl- channel
  • hyperpolarises cells
  • modulator not a ligand
  • allows Cl- channel to open for longer

increases the length or non-REM sleep but decreases REM sleep so will decrease effects of sleep

38
Q

EEG Limitations:

A
  • scalp electrodes are not sensitive
    enough to pick up individual action
    potentials
  • can not distinguish between
    excitatory, modulatory or
    inhibitory activity
  • limited anatomical specificity
    compared with other imaging tools
    such as fMRI
39
Q

Other physiological systems that contribute to sleep:

A
  • hormone systems
  • melatonin and cortisol rhythms
  • melatonin increases during sleep
  • cortisol decreases at the start and
    increases at the end
40
Q

Examples of Circadian Regulation:

A

cortisol high during the day, low at night
when put in light at night still persist but slightly altered

41
Q

Parasomnias:

A
  • disruptive sleep related disorders

Non-REM Parasomnias:
- sleep walking; still asleep but
exhibit limited awareness and
repsonsiveness to their
surroundings

 - night terrors: often scream in 
  their sleep, though most are not 
  responsive to outside stimuli 
  and will have no recollection of 
  the source of their terror upon 
  waking

REM Parasomnias:
- unusual vocalisations or
movements during REM sleep,
often as a reaction to a dream

42
Q

Circadian and Peripheral Cycle:

A

central pacemaker; when light positive signal, dark no signal

synchronises all hormonal systems

peripheral oscillators synchronise directed by the central pacemaker

jet lag is the lag between the central and peripheral

NSB (50 decks)

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