“…In addition, the muscle fibers of the tongue's extrinsic muscles are almost exclusively fast-contracting and mainly fatigue-resistant. 17,24,32,34 Although the cell population of the hypoglossal nucleus is composed of both intrinsic and extrinsic (for tongue shaping and positioning, respectively) muscle motoneurons, 2,21,37 the membrane properties (e.g., input resistance) of hypoglossal motoneurons appear to be relatively homogeneous. 27,38 However, the retractor and protrusor compartments of the hypoglossal nucleus may be characterized by different inputs and neurotransmitters.…”