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Figure 2: Relationship between the nervous system and the muscular system. (1) CNTF is released from the peripheral nerves and is one of the vital trophic factors for both the motor neuron and the myocytes. This growth factor is abundantly synthesized by Schwann cells. (2) MGF is locally released from the muscles and mainly activates satellite cells proliferation. (3) Some trophic factors (TrkB and myogenin) are innervation dependent. (4) Electrical impulse pattern modulates the muscle contractile properties and fiber-type profile.