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Electromyography is the measurement and analysis of the electrical activity in skeletal muscles. This technique is useful for diagnosing the health of the muscle tissue and the nerves that control them. [8] EMG measures action potentials, called Motor Unit Action Potentials (MUAPs), created during muscle contraction.
Additionally, the motor unit action potential is an all-or-none phenomenon - once the recruitment threshold (the stimulus intensity at which a motor unit begins to fire) is reached, it fires fully. Electrical stimulation of nerves reverses the recruitment order, due to the lower resistance of the larger motor neuron axons.
Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. [ 1 ] [ 2 ] EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram .
This is not a reflex, per se, in that the action potential travels from the site of the stimulating electrode in the limb to the spinal cord's ventral horn and back to the limb in the same nerve that was stimulated. The F-wave latency can be used to derive the conduction velocity of the nerve between the limb and spine.
Action potential propagation animation. The needle is normally attached to a recording device known as an electromyography machine. The results show the appearance of action potential or graded potential spikes. While interpretation of the results requires background knowledge, irregular data can be used to diagnose many diseases.
Intraoperative neurophysiological monitoring (IONM) or intraoperative neuromonitoring is the use of electrophysiological methods such as electroencephalography (EEG), electromyography (EMG), and evoked potentials to monitor the functional integrity of certain neural structures (e.g., nerves, spinal cord and parts of the brain) during surgery.
EEG, ECG, EOG and EMG are measured with a differential amplifier which registers the difference between two electrodes attached to the skin. However, the galvanic skin response measures electrical resistance and the Magnetoencephalography (MEG) measures the magnetic field induced by electrical currents ( electroencephalogram ) of the brain.
Using electromyography (EMG), the neural strategies of muscle activation can be measured. [6] Ramp-force threshold refers to an index of motor neuron size in order to test the size principle. This is tested by determining the recruitment threshold of a motor unit during isometric contraction in which the force is gradually increased.