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Human Physiological Measurement > EEG and EMG > Flashcards

EEG and EMG Flashcards

1
Q

What does EEG record

A

Electrical activity in the outer regions of the brain, primarily cortex
Records mass acuity of 1000s-millions of neurones firing

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2
Q

What is the mass discharge recorded by EEG

A
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3
Q

EEG Used to examine

A

Coma, brain defects, brain death, epilepsy

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4
Q

EEG Method

A

Electrodes placed at anatomically defined points
19 recordings, 1 reference

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5
Q

What is each electrode connected to

A

Input amplifier (1000-100,000 times)

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6
Q

What does EEG signal represent

A

Difference between voltages at 2 electrode sites

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7
Q

Bipolar montage

A

Each channel represents difference between 2 adjacent electrodfe

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8
Q

What is a montage

A

Can record eeg between different electrode combinations = montage

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9
Q

What is used as a common reference

A

Average signal

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10
Q

Normal activity is described in terms of:

A

Rhythmic activity and transients

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11
Q

Rhythm is activity is divided into…

A

Frequency bands

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12
Q

Describe delta waves

A

0-4Hz
Highest amplitude, slowest waves
Seen in slow wave sleep

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13
Q

Describe theta waves

A

4-7Hz
Young children
Drowsiness and arousal in adults
Meditation

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14
Q

Describe alpha waves

A

8-12Hz
Seen on closing eyes and relaxation
Disappears on opening eyes and mental maths

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15
Q

Describe beta waves

A

12-30Hz
Disappear with motor movement

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16
Q

Describe beta waves

A

12-30Hz
Disappear with motor movement
Associated with busy or anxious thinking

17
Q

Describe new-born waves

A

Mainly irregular theta and delta waves
Lacks rhythmic activity

18
Q

What is wakefulness characterised by

A

Alpha waves

19
Q

Drowsiness is characterised by:

A

Increased amplitude, slower alpha waves
Reduced HR and muscle artefact

20
Q

EEG and stage 1 sleep characterised by

A

Alpha waves suppressed, beta waves increase, some theta waves

21
Q

Stage 2 sleep:

A

Background beta and theta activity with some delta
Sleep spindles (sigma) 12-14Hz
Also K complexes - sharp wave followed by delta and spindle

22
Q

Stage 3 sleep:

A

Large amplitude delta waves <1Hz
Sleep spindles and K complexes remain

23
Q

Stage 4 sleep:

A

More prominent delta waves
Some K complexes

24
Q

Hyperventilation and EEG

A

Hypocapnia, decr BP, cerebral vasoconstriction
Increased theta waves

25
Q

Intermittent photic stimulation and EEG

A

Light lashes at 4-20Hz
Cause visual evoked potentials
Can be used to: identify sites of lesions and provoke epileptic activity

26
Q

Characteristic of epileptic EEG

A

Spike and wave activity
Localised in focal
Seen in every electrode in general
focal can spread giving secondary generalised activity

27
Q

What does EMG record

A

Electrical activity from skeletal muscles

28
Q

What type of electrodes are used on EMG

A

Surface electrodes
Intramuscular needle electrodes

29
Q

What is EMG used to distinguish

A

Neurogenic and myopathies causes of motor unit dysfunction

30
Q

What do nerve conduction studies involve

A

Stimulating nerve from 2 sides eg near elbow and at wrist

31
Q

EMG procedure

A

Fine needle inserted intramuscularly
Potentials from fibres in vicinity of tip recorded
Compound action potentials from fibres in the same motor unit recorded
Upon insertion brief discharge normally subsides after a few sewconds

32
Q

EMG activity is examined for what

A

Activity at rest
Number of motor units under voluntary control
Duration and amplitude of AP in each motor unit

33
Q

What happens in weak voluntary contraction

A

Series of motor unit potentials recorded as different motor units are recruited

34
Q

What happens in maximal contraction

A

Potentials overlap, impossible to identify single potentials

35
Q

What is amplitude determined by

A

The number of fibres within the motor unit

36
Q

Characteristics of myopathic disease

A

Number of muscle fibres in each unit reduced as fibre atrophy and die

Human Physiological Measurement (7 decks)

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