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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