Injury to a peripheral nerve, resulting in disconnection from its target (synapse), as well as fasciculation (spontaneous bursts of action potentials in degenerating motor neurons, with accompanying observable contractions in the entire motor unit) and fibrillation (spontaneous bursts of action potentials and accompanying very small twitches in isolated, denervated muscle fibers). Following denervation muscles usually become weak and atrophied (see figure below), and stretch reflexes are reduced. Peripheral neuropathy in diabetes mellitus can give rise to denervation.
