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*NEUROMUSCULAR ASPECTS OF EXERCISE > SLE2/MODULE 6- Motor Units TECHNIQUES > Flashcards

SLE2/MODULE 6- Motor Units TECHNIQUES Flashcards

1
Q

single motor unit refers to

A

the neuron + its fibers

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2
Q
A
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3
Q

the force exerted by a muscle depends on ____

A

the cumulative force that is contributed by the MUs that have been turned on

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4
Q

techniques to study single MU (2)

A

-intramuscular + subcutaneous electrodes
-spike-triggered averaging (STA)

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5
Q

techniques to study population of MUs (2)

A

-motor unit number estimation
-high-density grid-electrode arrays

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6
Q

who created the concentric needle electrode

A

Adrian + Bronk
-1929

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7
Q

who created the fine wire electrode

A

Bigland + Lippold
-1954

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8
Q

who created the fine wire with insulation removed

A

Gydkov et al.
-1984

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9
Q

how do electrodes communicate electrical signals

A

by working in pairs

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10
Q

what was the first intramuscular electrode developed

A

concentric needle electrode

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11
Q

what is concentric needle electrode made of

A

insulated copper wiring
-has exposd end
-placed within hydodermic needle

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12
Q

how is concentric needle electrode placed

A

placed into muscle + held in place with tiny plug

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13
Q

electrodes of concentric needle electrode

A

needle + wires make up the 2 electrodes
-exposed end of copper wiring projects into opening of needle + forms 1 electrode
-the other electrode is the needle itself

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14
Q

Bigland

A

the “queen of fatigue research”

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15
Q

what did Bigland + Lippold do

A

improved the selectivity if what wires could do
-you could select specific MUs you want to track in your research

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16
Q

what is fine wire electrode made of

A

insulated wires with bare ends that were inserted into a hypodermic needle
-no plug
-wire comes in OTHER end
-the sharp end of the needle has a bend

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17
Q

what made fine wire electrode different

A

signals recorded with these electrodes (the 2 wires within the needle) were a lot more selective
-highly variable because electrode could move during recording

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18
Q

what are the electrodes of the fine wire electrode

A

the 2 wires within the needle

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19
Q

fine wire with insulation removed

A

subcutaneous electrode
-improved upon the previous 2 electrodes (concentric needle + fine wire electrodes)

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20
Q

what is fine wire insulation removed electrode made of

A

-first wire has 2 recording sites + in between those 2 recording sites, there is 1 recording site on the second wire
-comprised 2 insulated wires
-wires were glued together so they did not move away from each other when placed in the muscle

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21
Q

where are intramuscular electrodes placed

A

directly into the muscle

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22
Q

where are subcutaneous electrodes placed

A

right on top of muscle fibers, but below subcutaneous tissue (fat/skin)

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23
Q

benefits of subcutaneous electrodes

A

not moving as much so not variable recordings
-BUT can only detect APs from superficial muscles because of the placement being right over the muscle

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24
Q

gold standard of electrodes

A

intramuscular electrodes
-recording is best
-more selective

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25
Q

in Diba’s opinion, which electrode is superior

A

subcutaneous
-because you can follow MUs across continuous longer term contractions

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26
Q

depending on the electrode, you can record from ____ fibers to ____ fibers belonging to different motor units

A

-1-3 fibers
-15-20 fibers

27
Q

motor unit APs typically have what phase

A

bi or triphasic phase

28
Q

diameter of electrode wires

A

50 microns
-the size of human hair

29
Q

electrode study- what did clicking sound indicate

A

there is a code that is created so that any time that wave form hits a certain amplitude there is a clicking sound projected through the speaker

30
Q

what technique can estimate the number of functioning MUs in a muscle

A

spike-triggered averaging (STA)

31
Q

spike-triggered averaging (STA)

A

basically using 1 MU’s function to get an estimate of the other MUs involved + their contributions to net force

-extracts the force contributed by a SINGLE MU to the net muscle force during sustained voluntary contractions
-APs produced by the MU trigger an averaging device that samples the muscle force at that time point
-calculates a running average from many triggered events

32
Q

what does STA technique do

A

extracts force developed by 1 motor unit during a sustained voluntary contraction
-we can measure the info from that small intramuscular recording to get an estimate of what the bigger picture of force contribution is

33
Q

spike-triggered averaging- what color is surface EMG

A

black

34
Q

spike-triggered averaging- what color is intramsucular EMG

A

green

35
Q

spike-triggered averaging- is it possible to observe the corresponding surface MU potential for any 1 discharge of a MU using a intramuscular EMG

A

NO
-however it is possible to generate an average of the surface EMG centered around the times of discharge of the MU

36
Q

spike-triggered averaging- how is the estimate shown

A

shown for an average generated using 10 discharges of the motor unit, and the estimate improves when 20 discharges are used as trigger events, and then 30, 40, 50, …140

37
Q

how can twitch force + the time to peak force (contractio time ) be measured in humans

A

spike-triggered averaging

38
Q

variations of STA

A

-researchers have modified STA over the past few years
-there are some variations on how it is applied in different protocols
-some papers use a classical method; others use an updated method

39
Q

what is the overarching idea of all STA variations

A

-to evaluate the mechanical activities of single MUs, the STA technique extracts the amount contributed by a single MU to the net muscle activity during sustained voluntary contractions
-the APs produced by the motor unit trigger an averaging device that samples the muscle activity at that particular time point + calculates a running average from many triggered events
-the average is the surface EMG, which is related to the muscle force

40
Q

limitations of STA

A

-how do factors that increase and decrease amplitude cancellation influence the size of the potentials extracted from the surface EMG?
-data collection takes about 2-3 minutes – this may confound the twitch profile by twitch potentiation and/or fatigability.
-generally recording units turned on at low forces, or low recruitment thresholds.

41
Q

MUNE

A

M wave / mean sMUAP

42
Q

MUNE technique stands for

A

motor unit number estimation (MUNE)

43
Q

MUNE technique

A

measures the number of motor neurons that innervate a muscle

44
Q

MUNE

iMUAP

A

intramuscular

45
Q

MUNE

sMUAP

A

surface level

46
Q

MUNE

how is M wave acquired

A

by shocking the nerve for the muscle of interest

47
Q

MUNE

how does M wave change

A

M wave changes in time + increases until it hits M max (as high or low as it can be)

48
Q

how do we calculate MUNE

A

M wave / average of sMUAP

49
Q

M wave is ____

A

artifically induced

50
Q

see slide 22/23 + notes

A
51
Q

which of the following statements about the spike-triggered averaging (STA) technique is correct?

a) the trigger event is an electric stimulus applied to the nerve
b) STA can be used to extract an average value from an intracellular EMG recording
c) amplitude is measured in ms
d) the size of the response would be similar for weak and strong motor units
e) the spike is the motor unit action potential

A

e) the spike is the motor unit action potential

52
Q

which of these statements about the MUNE technique is incorrect?

a) the size of the response of each motor unit will depend on its innervation number
b) the average amplitude of the motor unit responses is measured in voltage
c) the amplitude of the M wave is always greater than the sum of the recorded motor unit responses
d) the method can record the individual responses of all motor units in the muscle
e) the technique is a reasonable estimate but imperfect

A

d) the method can record the individual repsonses of all motor units in the muscle

53
Q

post-poliomyelitis syndrome

A

a neurological disorder that occurs in individuals who have recovered from paralytic poliomyelitis
-as aging occurs, muscles naturally shrink, but with this disorder, there is severe atrophy of the motor unit besides aging

54
Q

clinical features of post-poliomyelitis syndrome

A

-weakness
-fatigue
-pain

55
Q

normal count for extensor digitorum brevis

A

~200 with an amplitude of 100 uV

56
Q

amyotrophic lateral sclerosis (ALS)

A

degeneration of motor neurons

57
Q

see slide 30 for graphs

what have these 2 diseases done to this muscle? (depicting post-polio syndrome + ALS)

a) varies across individuals
b) most have fewer motor units
c) most have smaller amplitude potentials
d) will impact force output
e) all of these changes have occurred

A

e) all of these changes have occurred

58
Q

high-density grid-electrode arrays

A

look a MUs over a large surface of muscle
-composed of multiple detection points
-any location where there are 2 dots next to each other is a recording site
-shows it is possible to detect APs of motor units as they propagate
-consider these amped up on steroids of the usual bipolar electrode you would stick onto a muscle

59
Q

what was used to drive a prosthetic limb

A

EMG signals produced by REINNERVATED muscle
-targeted reinnervation

60
Q

there are various methods that can be used to study motor units, recording from either a SINGLE motor unit or MANY motor units within the entire population that innervate a single muscle

A
61
Q

methods to study single motor units provide information about either the ELECTRICAL or MECHANICAL OUTPUT by means of intramuscular or subcutaneous electrodes or via the SPIKE-TRIGGERED AVERAGING technique, respectively

A
62
Q

methods to study motor unit populations comprise high-density grid- electrode arrays and MOTOR UNIT NUMBER ESTIMATION techniques

A
63
Q

*be able to name the techniques
*recognize the labels or parts of each of the technique, what type of info they are getting, how that info is transferred from an analog thing that I am doing as a human being to see on a computer screen

A

*NEUROMUSCULAR ASPECTS OF EXERCISE (9 decks)

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