Fine, irregular contraction of individual fibers called

In the intact animal or human, healthy skeletal muscle does not contract except in response to stimulation of its motor nerve supply. Destruction of this nerve supply causes muscle atrophy. It also leads to abnormal excitability of the muscle and increases its sensitivity to circulating acetylcholine. Fine, irregular contractions of individual fibers (fibrillation) appear. This is the classic picture of a lower motor neuron lesion. If the motor nerve regenerates, the fibrillations disappear.Ref: Ganong's Review of Medical Physiology Twenty-Third Edition