Muscle ContractionHeartHeart RateIsometric ContractionMyocardial ContractionUterine ContractionHeart FailureMuscle, SmoothHeart DiseasesHeart TransplantationHeart Defects, CongenitalElectric StimulationCalciumMuscle, SkeletalFetal HeartGuinea PigsVasoconstrictionIsotonic ContractionHeart AtriaMyocardiumHeart ValvesTime FactorsMuscle, Smooth, VascularMuscle RelaxationNorepinephrineMuscle FatigueElectromyographyRabbitsDose-Response Relationship, DrugDogsHeart BlockPotassium ChlorideRats, WistarRats, Sprague-DawleyVasoconstrictor AgentsMyocytes, CardiacMusclesGastrointestinal MotilityAtropineAcetylcholineTracheaPhenylephrineHeart Arrest, InducedHeart Function TestsPeristalsisUrinary BladderNifedipineHemodynamicsMyocardial IschemiaVentricular Function, LeftVas DeferensCarbacholPerfusionMuscle TonusIleumMyosin Light ChainsAorta, ThoracicCalcium Channel BlockersIsoproterenolCardiotonic AgentsPotassiumTorquerho-Associated Kinases15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic AcidAction PotentialsCaffeineAdenosine TriphosphateMyosinsCoronary DiseaseVerapamilEnzyme InhibitorsMuscle Fibers, SkeletalAdrenergic alpha-AgonistsMotor NeuronsVasodilator AgentsMesenteric ArteriesArteriesCardiac Output, LowSerotoninPressureCardiomegalyReflexOxygen ConsumptionExcitation Contraction CouplingEndothelin-1MyometriumPapillary MusclesAortaMyofibrilsStroke VolumeEchocardiographySarcoplasmic ReticulumCardiomyopathy, DilatedAdrenergic beta-AntagonistsSympathetic Nervous SystemHistamineCardiomyopathiesBiomechanical PhenomenaHeart Rate, FetalEndothelins