Figure 3.

Increased Motor Neuron Terminal Sprouting after Motor Neuron Death. In healthy adults, each muscle fiber is innervated by a single motor neuron. With neurodegenerative disease or trauma, some motor neurons die (or undergo axonal detachment) and their muscle fibers are denervated. The adjacent motor neuron terminals sprout to reinnervate the denervated muscle fibers. As the pathology progresses, the number of muscle fibers innervated by each motor neuron increases up to 5- to 8-fold preserving ventilatory and airway protective functions of respiratory motor network, However, further sprouting and increased discharge activity may lead to neuromuscular transmission problems and muscle dysfunction.