Papillary MusclesMuscle ContractionMusclesMyocardial ContractionIsometric ContractionMuscle, SmoothMuscle, SkeletalMuscle ProteinsMuscle, Smooth, VascularGuinea PigsChordae TendineaeMuscle Fibers, SkeletalMitral Valve InsufficiencyHeartMuscle DevelopmentMitral ValveMuscle FatigueUterine ContractionElectric StimulationCalciumFerretsMuscle RelaxationAction PotentialsMyocardiumHeart VentriclesRabbitsMuscle Fibers, Fast-TwitchMuscle DenervationMuscle Fibers, Slow-TwitchAequorinMyocytes, Smooth MuscleElectromyographyTime FactorsDogsCatsMitochondria, MuscleHeart Rupture, Post-InfarctionMuscle SpindlesIsoproterenolRats, WistarMyofibrilsCineradiographyDose-Response Relationship, DrugVentricular FunctionDepression, ChemicalNeck MusclesMembrane PotentialsOculomotor MusclesBiomechanical PhenomenaMuscle, StriatedHeart RuptureElectrophysiologyPurkinje FibersRespiratory MusclesMuscle WeaknessVasoconstrictionQuadriceps MuscleRats, Sprague-DawleyRyanodineAbdominal MusclesMuscle CellsPotassium ChlorideSarcoplasmic ReticulumPotassiumEndocardiumPhenylephrineNifedipineStimulation, ChemicalMitral Valve AnnuloplastyCalcium Channel BlockersNorepinephrineMasseter MuscleOuabainVerapamilMasticatory MusclesFacial MusclesIsotonic ContractionCardiomyopathiesCross CirculationIntercostal MusclesAnti-Arrhythmia AgentsTracheaCaffeineMicroelectrodesSarcolemmaHeart Conduction SystemMotor NeuronsAdrenergic beta-AgonistsCells, CulturedMuscular AtrophySarcomeresCardiotonic AgentsEchocardiographyAcetylcholineStress, MechanicalMyosin Heavy ChainsHeart RateHindlimbPerfusionCarnivora