6.2 Signals of the Muscles and Motions

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Muscle fiber

Individual motorunit action potentials

(MUAPTs)

Needle

electrode

raw-EMG (single channel)

α-Motoneuron

Spinal cord

nerve

Fig. 6.6: Schematic representation of a motor unit (left) consisting of a α neuron and several muscle

fibers: The cell body of the α neuron in the anterior horn of the spinal cord emits the action poten-

tial, which then innervates action potentials in the muscle fibers via the motor end plates of the

branched axon at the junctions. The formation of the EMG sequence results from the sum of the

individual action potentials of the involved motor units (MU)⁷ (right).

themselves (myopathy) or the neurons that excite the muscle fibers (neuropathy) (cf.

Figure 6.6).

Basically, an EMG can be recorded with the same technique as already presen-

ted for the measurement of an ECG. EMG needles allow the contacting of single motor

units up to the detection of the action potential of single muscle fibers. This is not

possible with surface electrodes due to their much poorer spatial resolution. Surface

electrodes in the form of electrode arrays, on the other hand, are better suited for stud-

ies of the spatial and temporal propagation of the action potential in the individual