Figure 2: Motor unit action potentials
obtained by needle electromyography examination: a) normal, b) myopathic,
and c) neurogenic. In myopathies, the reduced number of muscle fibres
per motor unit leads to less summation effect, resulting in small and
spiky signals. In neuropathies, the denervated muscle fibres will become
reinnervated by other surviving nerve endings, thereby expanding the motor
unit territory by up to 40%. Activation of this enlarged motor unit results
in a large and bizzare-looking discharge. (Each division in the vertical
axis represents 200
V
for a) and b) and 500V
for c).)
