SLE2/MODULE 6- Motor Units TECHNIQUES

Question 1

single motor unit refers to

Answer 1

the neuron + its fibers

Question 3

the force exerted by a muscle depends on ____

Answer 3

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

Question 4

techniques to study single MU (2)

Answer 4

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

Question 5

techniques to study population of MUs (2)

Answer 5

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

Question 6

who created the concentric needle electrode

Answer 6

Adrian + Bronk
-1929

Question 7

who created the fine wire electrode

Answer 7

Bigland + Lippold
-1954

Question 8

who created the fine wire with insulation removed

Answer 8

Gydkov et al.
-1984

Question 9

how do electrodes communicate electrical signals

Answer 9

by working in pairs

Question 10

what was the first intramuscular electrode developed

Answer 10

concentric needle electrode

Question 11

what is concentric needle electrode made of

Answer 11

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

Question 12

how is concentric needle electrode placed

Answer 12

placed into muscle + held in place with tiny plug

Question 13

electrodes of concentric needle electrode

Answer 13

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

Question 14

Bigland

Answer 14

the “queen of fatigue research”

Question 15

what did Bigland + Lippold do

Answer 15

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

Question 16

what is fine wire electrode made of

Answer 16

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

Question 17

what made fine wire electrode different

Answer 17

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

Question 18

what are the electrodes of the fine wire electrode

Answer 18

the 2 wires within the needle

Question 19

fine wire with insulation removed

Answer 19

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

Question 20

what is fine wire insulation removed electrode made of

Answer 20

-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

Question 21

where are intramuscular electrodes placed

Answer 21

directly into the muscle

Question 22

where are subcutaneous electrodes placed

Answer 22

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

Question 23

benefits of subcutaneous electrodes

Answer 23

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

Question 24

gold standard of electrodes

Answer 24

intramuscular electrodes
-recording is best
-more selective

Question 25

in Diba's opinion, which electrode is superior

Answer 25

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

Question 26

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

Answer 26

-1-3 fibers -15-20 fibers

Question 27

motor unit APs typically have what phase

Answer 27

bi or triphasic phase

Question 28

diameter of electrode wires

Answer 28

50 microns -the size of human hair

Question 29

electrode study- what did clicking sound indicate

Answer 29

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

Question 30

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

Answer 30

spike-triggered averaging (STA)

Question 31

spike-triggered averaging (STA)

Answer 31

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

Question 32

what does STA technique do

Answer 32

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

Question 33

spike-triggered averaging- what color is surface EMG

Answer 33

black

Question 34

spike-triggered averaging- what color is intramsucular EMG

Answer 34

green

Question 35

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

Answer 35

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

Question 36

spike-triggered averaging- how is the estimate shown

Answer 36

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

Question 37

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

Answer 37

spike-triggered averaging

Question 38

variations of STA

Answer 38

-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

Question 39

what is the overarching idea of all STA variations

Answer 39

-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

Question 40

limitations of STA

Answer 40

-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.

Question 41

MUNE

Answer 41

M wave / mean sMUAP

Question 42

MUNE technique stands for

Answer 42

motor unit number estimation (MUNE)

Question 43

MUNE technique

Answer 43

measures the number of motor neurons that innervate a muscle

Question 44

# MUNE iMUAP

Answer 44

intramuscular

Question 45

# MUNE sMUAP

Answer 45

surface level

Question 46

# MUNE how is M wave acquired

Answer 46

by shocking the nerve for the muscle of interest

Question 47

# MUNE how does M wave change

Answer 47

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

Question 48

how do we calculate MUNE

Answer 48

M wave / average of sMUAP

Question 49

M wave is ____

Answer 49

artifically induced

Question 50

see slide 22/23 + notes

Question 51

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

Answer 51

e) the spike is the motor unit action potential

Question 52

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

Answer 52

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

Question 53

post-poliomyelitis syndrome

Answer 53

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

Question 54

clinical features of post-poliomyelitis syndrome

Answer 54

-weakness -fatigue -pain

Question 55

normal count for extensor digitorum brevis

Answer 55

~200 with an amplitude of 100 uV

Question 56

amyotrophic lateral sclerosis (ALS)

Answer 56

degeneration of motor neurons

Question 57

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

Answer 57

e) all of these changes have occurred

Question 58

high-density grid-electrode arrays

Answer 58

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

Question 59

what was used to drive a prosthetic limb

Answer 59

EMG signals produced by REINNERVATED muscle -targeted reinnervation

Question 60

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

Question 61

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

Question 62

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

Question 63

*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