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Autonomic Nervous Autonomic Nervous SystemSystem

Autonomic Nervous Autonomic Nervous SystemSystem

Chapter 11

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ComparisonComparisonComparisonComparison

• Somatic systems- conscious awareness

• Autonomic sensory - not consciously perceivedMonitors internal conditions- blood gasses,

viscera operation, etc

• Autonomic motor- cardiac muscle, smooth muscle & glandsOften adjustment of internal controls in

relation to whole body needs

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Motor pathwaysMotor pathwaysMotor pathwaysMotor pathways

• Somatic motor neurons go directly from spinal cord to skeletal muscle

• Autonomic motor systems includes two motor neurons:

• Preganglionic neuron from CNS to autonomic neuron from cell body in ganglion to effector

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DivisionsDivisionsDivisionsDivisions

•Sympathetic division•Parasympathetic division•both divisions often innervate the

same effector•They have opposite effects•E.g. sympathetic stimulates heart

rate and parasympathetic slows it

Figure 11.1a

Figure 11.1b

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Sympathetic divisionSympathetic divisionSympathetic divisionSympathetic division

•Thoracolumbar division- outflow from thoracic & lumbar

segments of spinal cord

•Preganglionic fibers –•From lateral horns via ventral

roots• to sympathetic ganglia•synapse with postganglionic cells

in ganglia

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Sympathetic GangliaSympathetic GangliaSympathetic GangliaSympathetic Ganglia

• Sympathetic Trunk GangliaVertical rows on either side of vertebral

columnPost synaptic fibers mostly got to organs

above diaphragm

• Prevertebral gangliaAnterior to vertebral column- celiac, superior mesenteric & inferior

mesentericInnervate organs below diaphragm

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Preganglionic RoutingPreganglionic RoutingPreganglionic RoutingPreganglionic Routing

• To postganglionic neuron• 1. in trunk ganglion at level of root• 2. In ganglion higher or lower in chain• 3. in prevertebral ganglion• 4.Directly to target organ-adrenal

medullaaverage preganglionic neuron synapses

with 17 postganglionic neurons

Figure 11.2

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Parasympathetic Parasympathetic NeuronsNeurons

Parasympathetic Parasympathetic NeuronsNeurons

•Output at top-medulla nucleiCranial nerves II, VII,IX, X

•Bottom of spinal cord- sacral nerves

•Synapse in terminal gangliaNear or in the innervated organ

• localized to single effector organ

Figure 11.3

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NeurotransmittersNeurotransmittersNeurotransmittersNeurotransmitters

• Acetylcholine-All preganglionic fibers terminalsparasympathetic postganglionic terminalsA few postganglionic sympathetic terminalsShort-lived effects

• Norepinephrine-Most postganglioic sympathetic terminalsLonger effectsAmplified by adrenal release with epinephrine

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ANS ActivityANS ActivityANS ActivityANS Activity

•Balance between sympathetic & parasympathetic “tone” regulated through hypothalamus

•Only sympathetic to:Sweat glands, arrrector pili muscles,

kidneys, spleen, blood vessels & adrenal medulla

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Sympathetic EffectsSympathetic EffectsSympathetic EffectsSympathetic Effects

•fight-or-flight activitiesDilate pupilsIncrease HR, heart contraction & BPDilate airwaysConstrict blood vessels to non

essential organs: kidneys, GI tractDilate vessels to muscles, cardiac

muscle, liver & adiposeMobilize nutrients: glucose & fats

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Parasympathetic EffectsParasympathetic EffectsParasympathetic EffectsParasympathetic Effects

• Rest-and–digest act ivies• SLUDD

SalvationLacrimationUrinationDigestionDefecationDecrease- HR, airway diameter, pupil

diameter