31-07-2012, 11:15 AM
Electromyograph (EMG)
Electromyograph.ppt (Size: 174.5 KB / Downloads: 75)
What is EMG?
EMG is an instrument used for recording the electrical activity of the muscles.
Modes of EMG
Electromyogram:-
The electromyogram(EMG) is a recording of the electrical activity of muscles, for the study of muscular contraction.
Electromyograph:-
This EMG signals are picked up by means of metal electrodes attached to the muscles wall and then amplified and recorded by a suitable instrument which is called Electromyograph.
Electromyography:-
The recording process of electrical activity of muscles that is the action potential of muscles, is called Electromyography.
EMG Electrodes:
Electrodes used for EMG maybe-
1.surface electrode.
2.needle electrode.
3.fine wire electrode.
Surface, needle and fine wire electrodes are all used for different type of EMG measurement. The surface electrodes are generally used where induction are suitable, needle or fine wire electrodes that penetrate the skin and contact the muscle fiber to be measured are needed.
In EMG recording bipolar recording is usually used where by two electrodes are placed near the muscle and differential potential between these electrodes is recorded and observed. The electrodes maybe placed either externally on the skin over the muscle (in case of surface electrodes), or inside the muscle by means of needle electrodes.
RECODING PROCESS OF EMG:
The surface electrodes may be disposable, adhesive types or the ones which can be used repeatedly.
A ground electrode is necessary for providing a common reference for measurement. These electrodes pick up the potential produced by the contracting muscle fibers. The signal can then be amplified and displayed on the screen of a cathode ray tube. It is also applied to an audio amplifier connected to a loudspeaker. A trained EMG interpreter can diagnose various muscular disorders by listening to the sound produced when the muscle potentials are fed to the loudspeaker. The block diagram shows a typical set-up for EMG recordings. The oscilloscope displays EMG waveforms. The tape recorder is included in the system to facilitate playback and study of the EMG sound waveforms at a later convenient time.
Application for EMG:
To distinguishing the nerve form muscle disease i.e. myopathic or neropathic disease.
To detect the partial paralysis.
To detect the fibrillation and fasciculation.
The measure the nerve conduction in nerve for diagnosis the damage myelin sheath where it is slow.