Muscle TonusMuscle HypertoniaMusclesMuscle, SmoothMuscle ContractionMuscle ProteinsNeck MusclesMuscle, SkeletalMuscle Fibers, SkeletalMuscle, Smooth, VascularMuscle DevelopmentBrain ChemistryAutonomic Nervous SystemBrain InjuriesParasympathetic Nervous SystemBrain NeoplasmsMuscle FatigueMuscle Fibers, Fast-TwitchRats, WistarMuscle Denervation