Basic EMG Flashcards
What determines the duration of the MUAP?
The number of muscle fibers within a motor unit
What happens to the MUAP duration when the territory of a motor unit increases?
The MUAP duration increases
What effects do age and termperature have on MUAP duration?
- Increasing age = increasing MUAP duration
- Decreasing temperature = increasing MUAP duration
Polyphasia in a MUAP is a measure of what?
Synchrony. The degree to which muscle fibers in a motor unit fire at the same time. The greater the polyphasia the less synchronous the muscle fibers in a motor unit are firing.
What determines MUAP amplitude?
It’s a reflection of the few muscle fibers that are closest to the needle. Most of the muscle fibers contribute very little to the amplitude.
What is the slowest that a MUAP can fire under voluntary control?
4 to 5 Hz
Anything less is not under voluntary control
How is sound correlated with MUAP duration and amplitude?
- Duration is correlated with pitch
- Increased duration = lower pitch
- Amplitude is correlated with volume
- Increased amplitude = increased volume
What is the ratio of the firing frequeny to the number of motor units firing?
5:1
Thus when the frequency is 10 Hz, 2 motor units will be visible on the screen
What is the typical max firing frequency for most muscles?
30 - 50 Hz
The motor neuron/axon is the generator for what waveforms?
- Fasciculation
- Myokymia
- Tetany
- Cramp
- Neuromyotonia
The neuromuscular junction is the generator for what waveform?
End-plate noise
The terminal axon is the generator for what waveform?
End-plate spike
The muscle fiber is the generator for what waveforms?
- Fibrillations
- Positive sharp waves
- Myotonia
Multiple muscle fibers is the generator for what waveforms?
Complex repetitive discharges
The Neuromuscular junction is the generator for what waveform?
End plate noise
The terminal axon is the generator for what waveform?
End plate spike
Multiple muscle fibers is the generator for what waveform?
Complex repetitive discharges
The muscle fiber is the generator for what waveforms?
Fibrillations
Positive sharp waves
Myotonic discharges
