Lecture 7-9 - Motor System & Electromyography Flashcards
What is the thick filament of a muscle fibre?
Myosin
What is the thin filament of a muscle fibre?
Actin
What is the basic explanation of a power stroke?
Calcium binds with troponin, moving tropomyosin aside, exposing the actin-myosin binding site, and triggering power strokes to begin occurring
What is a motor unit?
a single motorneuron and all of the muscle fibres it innervates
What is a motor pool?
all of the motor units innervating a given muscle
What are the type of muscle fibres?
Type I (SO, S), IIA (FO, FR), IIAB (FOG, FI), IIB (FG, FF)
Which muscle fibres fatigue slowly?
Slow oxidative
What are slow twitch muscle fibres?
Oxidative
What are fast, fatiguable fibres?
Glycolytic
Which muscle fibres are darker in a myoglobin stain?
Slow oxidative fibres (aerobic)
Are smaller motor units more or less excitable than larger ones?
more!
What motor units ‘get recruited’ first?
smaller motor units
What motor units turn off first?
Larger motor units
T/F: Larger MU’s innervate more muscle fibres
True
What does a surface electromyography measure?
Average overall output of a muscle
Where are the electrodes placed in a EMG?
Placed of the muscle belly (thickest part) and aligns with the direction of the muscle fibres (pennation angle)
How do we prep for a EMG?
Clean skin, lightly abrade to remove dead skin cells, sometimes shave
What is rectification in terms of EMG processing?
absolute value of the EMG
What is smoothing in terms of EMG processing?
averages the rectified EMG
What is MVC?
Maximal Voluntary Contraction
What is indwelling EMG used for?
To measure smaller or deeper muscles
What is a benefit of indwelling EMG?
you can extract single MU spikes
What is the recruitment order of motor units?
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
How does training effect motor neurson?
With strength training we can increase the amplitude of EMG during a MVC
What about the muscle force production changes with training?
MU spiking patterns
What are the MU spiking pattern changes thought to be caused by?
Modulation in cortical input onto motorneurons (control of muscle by brain) and changes in muscle fibre type composition
What happens to EMG results during bedrest, casting or while in space?
EMG amplitude decreases
How does a EMG correlate with force output?
Linearly
What happens to our EMG as we train?
Larger electrical outputs
What are the difference between indwelling and surface EMG?
Indwelling:
- can look at smaller and deeper muscles
- can sort and categorize MU’s
Surface:
- gives us overall information of muscles (all MU’s)
What do smaller MU’s require less input?
They have less SA for charges to leak out
