BaroreflexHeart RatePressoreceptorsSympathetic Nervous SystemBlood PressurePhenylephrineCarotid SinusVagus NerveAutonomic Nervous SystemReflexNitroprussideSolitary NucleusBradycardiaValsalva ManeuverDenervationCardiovascular SystemConsciousnessSupine PositionTrimethaphanArteriesVasoconstrictor AgentsReflex, AbnormalCardiovascular Physiological PhenomenaHeartLower Body Negative PressureTilt-Table TestParasympathetic Nervous SystemHypotension, OrthostaticVasomotor SystemGanglionic BlockersCarotid ArteriesHead-Down TiltTachycardiaPeroneal NervePostureDizzinessHypertensionAutonomic Nervous System DiseasesCentral Venous PressureHemodynamicsAutonomic DenervationVagus Nerve DiseasesElectrocardiographyMedulla OblongataSympathomimeticsRats, Sprague-DawleyModels, CardiovascularPhotoplethysmographyVasodilator AgentsCardiovascular DeconditioningGravity SuitsPulseAntihypertensive AgentsMicroinjectionsKidneyFourth VentricleSympathetic Fibers, PostganglionicChemoreceptor CellsAngiotensin IIVascular ResistanceExerciseInfusions, IntraventricularArterial PressurePure Autonomic FailureRats, Inbred SHRAtropine DerivativesNorepinephrineRespirationInjections, IntraventricularSyncope, VasovagalMuscle, SkeletalSinus of ValsalvaDogsHypotensionNeckRespiratory MechanicsNitroglycerinVagotomyTelemetryAdrenergic FibersSuctionLosartanSignal Processing, Computer-AssistedSinoatrial Node