Lecture 7-9 - Motor System & Electromyography

Question 1

What is the thick filament of a muscle fibre?

Answer 1

Myosin

Question 2

What is the thin filament of a muscle fibre?

Answer 2

Actin

Question 3

What is the basic explanation of a power stroke?

Answer 3

Calcium binds with troponin, moving tropomyosin aside, exposing the actin-myosin binding site, and triggering power strokes to begin occurring

Question 4

What is a motor unit?

Answer 4

a single motorneuron and all of the muscle fibres it innervates

Question 5

What is a motor pool?

Answer 5

all of the motor units innervating a given muscle

Question 6

What are the type of muscle fibres?

Answer 6

Type I (SO, S), IIA (FO, FR), IIAB (FOG, FI), IIB (FG, FF)

Question 7

Which muscle fibres fatigue slowly?

Answer 7

Slow oxidative

Question 8

What are slow twitch muscle fibres?

Answer 8

Oxidative

Question 9

What are fast, fatiguable fibres?

Answer 9

Glycolytic

Question 10

Which muscle fibres are darker in a myoglobin stain?

Answer 10

Slow oxidative fibres (aerobic)

Question 11

Are smaller motor units more or less excitable than larger ones?

Answer 11

more!

Question 12

What motor units ‘get recruited’ first?

Answer 12

smaller motor units

Question 13

What motor units turn off first?

Answer 13

Larger motor units

Question 14

T/F: Larger MU’s innervate more muscle fibres

Answer 14

True

Question 15

What does a surface electromyography measure?

Answer 15

Average overall output of a muscle

Question 16

Where are the electrodes placed in a EMG?

Answer 16

Placed of the muscle belly (thickest part) and aligns with the direction of the muscle fibres (pennation angle)

Question 17

How do we prep for a EMG?

Answer 17

Clean skin, lightly abrade to remove dead skin cells, sometimes shave

Question 18

What is rectification in terms of EMG processing?

Answer 18

absolute value of the EMG

Question 19

What is smoothing in terms of EMG processing?

Answer 19

averages the rectified EMG

Question 20

What is MVC?

Answer 20

Maximal Voluntary Contraction

Question 21

What is indwelling EMG used for?

Answer 21

To measure smaller or deeper muscles

Question 22

What is a benefit of indwelling EMG?

Answer 22

you can extract single MU spikes

Question 23

What is the recruitment order of motor units?

Answer 23

Smaller MU get recruited first (slow oxidative muscle fibres), then larger ones get recruited sense they require more stimulus. Larger MU’s get de-recruited first, smaller ones last

Question 24

How does training effect motor neurson?

Answer 24

With strength training we can increase the amplitude of EMG during a MVC

Question 25

What about the muscle force production changes with training?

Answer 25

MU spiking patterns

Question 26

What are the MU spiking pattern changes thought to be caused by?

Answer 26

Modulation in cortical input onto motorneurons (control of muscle by brain) and changes in muscle fibre type composition

Question 27

What happens to EMG results during bedrest, casting or while in space?

Answer 27

EMG amplitude decreases

Question 28

How does a EMG correlate with force output?

Answer 28

Linearly

Question 29

What happens to our EMG as we train?

Answer 29

Larger electrical outputs

Question 30

What are the difference between indwelling and surface EMG?

Answer 30

Indwelling:
- can look at smaller and deeper muscles
- can sort and categorize MU’s

Surface:
- gives us overall information of muscles (all MU’s)

Question 31

What do smaller MU’s require less input?

Answer 31

They have less SA for charges to leak out