14Autonomic Nervous System (ANS)ANS Versus Somatic Nervous System (SNS)EffectorsEfferent PathwaysNeurotransmitter EffectsComparison of Somatic and Autonomic SystemsDivisions of the ANSRole of the Parasympathetic DivisionRole of the Sympathetic DivisionAnatomy of ANSSlide 12Parasympathetic Division OutflowSlide 14Sympathetic OutflowSlide 16Sympathetic Trunks and PathwaysSlide 18Slide 19Pathways with Synapses in Chain GangliaPathways to the HeadPathways to the ThoraxPathways with Synapses in Collateral GangliaPathways to the AbdomenPathways to the PelvisPathways with Synapses in the Adrenal MedullaVisceral ReflexesSlide 28Referred PainNeurotransmitters and ReceptorsCholinergic ReceptorsNicotinic ReceptorsMuscarinic ReceptorsAdrenergic ReceptorsEffects of DrugsDrugs that Influence the ANSSlide 37Interactions of the Autonomic DivisionsSympathetic ToneParasympathetic ToneCooperative EffectsUnique Roles of the Sympathetic DivisionThermoregulatory Responses to HeatRelease of Renin from the KidneysMetabolic EffectsLocalized Versus Diffuse EffectsEffects of Sympathetic ActivationLevels of ANS ControlSlide 49Hypothalamic ControlAgingEmbryonic Development of the ANSDevelopmental Aspects of the ANS114The Autonomic Nervous System2Autonomic Nervous System (ANS)The ANS consists of motor neurons that: Innervate smooth and cardiac muscle and glandsMake adjustments to ensure optimal support for body activitiesOperate via subconscious controlHave viscera as most of their effectors3ANS Versus Somatic Nervous System (SNS)The ANS differs from the SNS in the following three areasEffectorsEfferent pathwaysTarget organ responses4EffectorsThe effectors of the SNS are skeletal musclesThe effectors of the ANS are cardiac muscle, smooth muscle, and glands5Efferent PathwaysHeavily myelinated axons of the somatic motor neurons extend from the CNS to the effectorAxons of the ANS are a two-neuron chainThe preganglionic (first) neuron has a lightly myelinated axonThe ganglionic (second) neuron extends to an effector organ6Neurotransmitter EffectsAll somatic motor neurons release Acetylcholine (ACh), which has an excitatory effectIn the ANS:Preganglionic fibers release AChPostganglionic fibers release norepinephrine or ACh and the effect is either stimulatory or inhibitoryANS effect on the target organ is dependent upon the neurotransmitter released and the receptor type of the effector7Comparison of Somatic and Autonomic SystemsFigure 14.28Divisions of the ANSThe two divisions of the ANS are the sympathetic and parasympatheticThe sympathetic mobilizes the body during extreme situationsThe parasympathetic performs maintenance activities and conserves body energy The two divisions counterbalance each other’s activity9Role of the Parasympathetic DivisionThe parasympathetic division is the “rest-and-digest” systemConcerned with keeping body energy use lowInvolves the D activities – digestion, defecation, and diuresisIts activity is illustrated in a person who relaxes after a mealBlood pressure, heart rate, and respiratory rates are lowGastrointestinal tract activity is highThe skin is warm and the pupils are constricted10Role of the Sympathetic DivisionThe sympathetic division is the “fight-or-flight” systemInvolves E activities – exercise, excitement, emergency, and embarrassmentPromotes adjustments during exercise – blood flow to organs is reduced, flow to muscles is increasedIts activity is illustrated by a person who is threatenedHeart rate increases, and breathing is rapid and deepThe skin is cold and sweaty, and the pupils dilateGastroinstestinal Tract motility decreases11Anatomy of ANSDivision Origin of Fibers Length of FibersLocation of GangliaSympathetic Thoracolumbar region of the spinal cordShort preganglionic and long postganglionicClose to the spinal cordParasympathetic Brain and sacral spinal cordLong preganglionic and short postganglionicIn the visceral effector organs12Anatomy of ANSFigure 14.313Parasympathetic Division OutflowCranial Outflow Cranial Nerve Ganglion Effector Organ(s)Occulomotor (III) Ciliary EyeFacial (VII) PterygopalatinSubmandibularSalivary, nasal, and lacrimal glandsGlossopharyngeal (IX)Otic Parotid salivary glandsVagus (X) Located within the walls of target organsHeart, lungs, and most visceral organsSacral Outflow S2-S4Located within the walls of the target organsLarge intestine, urinary bladder, ureters, and reproductive organs14Parasympathetic Division OutflowFigure 14.415Sympathetic OutflowArises from spinal cord segments T1 through L2Sympathetic neurons produce the lateral horns of the spinal cordPreganglionic fibers pass through the white rami communicantes and synapse in the chain (paravertebral) gangliaFibers from T5-L2 form splanchnic nerves and synapse with collateral ganglia Postganglionic fibers innervate the numerous organs of the body16Sympathetic OutflowFigure 14.517Sympathetic Trunks and PathwaysThe paravertebral ganglia form part of the sympathetic trunk or chainTypically there are 23 ganglia – 3 cervical, 11 thoracic, 4 lumbar, 4 sacral, and 1 coccygeal18Sympathetic Trunks and PathwaysFigure 14.619Sympathetic Trunks and PathwaysA preganglionic fiber follows one of three pathways upon entering the paravertebral gangliaSynapse with the ganglionic neuron within the same ganglionAscend or descend the sympathetic chain to synapse in another chain ganglionPass through the chain ganglion and emerge without synapsing20Pathways with Synapses in Chain GangliaPostganglionic axons enter the ventral rami via the gray rami communicantesThese fibers innervate sweat glands and arrector pili musclesRami communicantes are associated only with the sympathetic division21Pathways to the HeadPreganglionic fibers emerge from T1-T4 and synapse in the superior cervical ganglionThese fibers:Serve the skin and blood vessels of the headStimulate dilator muscles of the irisInhibit nasal and salivary glands22Pathways to the ThoraxPreganglionic fibers emerge from T1-T6 and synapse in the cervical chain gangliaPostganglionic fibers emerge from the middle and inferior cervical ganglia and enter nerves C4-C8These fibers innervate the heart via the cardiac plexus, as well as innervating the thyroid and the skinOther T1-T6 preganglionic fibers synapse in the nearest chain gangliaPostganglionic