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Autonomic Nervous System 11
Unit 1
Chapter 11
Comparison
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• Somatic systems- conscious awareness
• Autonomic sensory - not consciously
perceived
• Autonomic motor- cardiac muscle,
smooth muscle & glands
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Monitors internal conditions- blood gasses,
viscera operation, etc
Often adjustment of internal controls in relation to
whole body needs
• 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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Motor pathways
• 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
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Divisions
Figure 11.1a
Figure 11.1b
Sympathetic division
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• Thoracolumbar division• Preganglionic fibers –
• From lateral horns via ventral roots
• to sympathetic ganglia
• synapse with postganglionic cells in
ganglia
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outflow from thoracic & lumbar segments
of spinal cord
Sympathetic Ganglia
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• Sympathetic Trunk Ganglia
Vertical rows on either side of vertebral column
Post synaptic fibers mostly got to organs above
diaphragm
Anterior to vertebral columnceliac, superior mesenteric & inferior mesenteric
Innervate organs below diaphragm
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• Prevertebral ganglia
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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
medulla
average preganglionic neuron synapses
with 17 postganglionic neurons
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Preganglionic Routing
Figure 11.2
Parasympathetic Neurons
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• Output at top-medulla nuclei
Cranial nerves II, VII,IX, X
Near or in the innervated organ
• localized to single effector organ
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• Bottom of spinal cord- sacral nerves
• Synapse in terminal ganglia
Figure 11.3
Neurotransmitters
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• Acetylcholine-
• NorepinephrineMost postganglioic sympathetic terminals
Longer effects
Amplified by adrenal release with epinephrine
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All preganglionic fibers terminals
parasympathetic postganglionic terminals
A few postganglionic sympathetic terminals
Short-lived effects
ANS Activity
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Sweat glands, arrrector pili muscles,
kidneys, spleen, blood vessels & adrenal
medulla
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• Balance between sympathetic &
parasympathetic “tone” regulated
through hypothalamus
• Only sympathetic to:
Sympathetic Effects
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Dilate pupils
Increase HR, heart contraction & BP
Dilate airways
Constrict blood vessels to non essential
organs: kidneys, GI tract
Dilate vessels to muscles, cardiac muscle,
liver & adipose
Mobilize nutrients: glucose & fats
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• fight-or-flight activities
Parasympathetic Effects
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Salvation
Lacrimation
Urination
Digestion
Defecation
Decrease- HR, airway diameter, pupil diameter
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• Rest-and–digest act ivies
• SLUDD