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Human Anatomy
The Autonomic Nervous System
ANS
ANS
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Regulates various physiological
processes unconsciously, for instance:
Cardiovascular
Respiration
Digestion
Body temperature
Excretion
2 Subdivisions of the ANS
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Sympathetic NS
“fight or flight”
Parasympathetic NS
“rest and repose”
Anatomy of ANS
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Consists of only 2 neurons
Preganglionic neuron (#1)
Ganglionic neuron (#2)
The ganglion is a structure where
the axon of the preganglionic neuron synapses
(release of neurotransmitter) with
the ganglionic neuron (dendrite or cell body)
The axon of the ganglion synapses with the
target cell or organ.
Anatomy of the ANS
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Differences between sympathetic and
parasympathetic are:
Location of preganglionic (#1) cell body
Location of the ganglia
Neurotransmitters released at synapses
Effects on target organs
Sympathetic Anatomy
• Once again, just 2 cells
• Preganglion (#1) cell body in gray matter
of spinal cord ---- levels T1 – L2
• Thoracolumbar system
Sympathetic Anatomy
Thoracolumbar
Sympathetic Anatomy
• Synapse of preganglionic (#1) with
ganglionic (#2) neurons happens in the
ganglion
• 3 cervical ganglia
• 3 abdominal ganglia
• Neurotransmitter is acetylcholine (ACh)
Sympathetic Anatomy
Thoracolumbar
Sympathetic Ganglia
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Paravertebral ganglia
Cervical
Superior
Middle
Inferior
Abdominal
Celiac
Superior mesenteric
Inferior mesenteric
Sympathetic Anatomy
Thoracolumbar
Sympathetic Anatomy
• Ganglionic (#2) axons are relatively long
• Synapse at target cell or organ
• Neurotransmitter is norepinephrine (NE)
Sympathetic Anatomy
Thoracolumbar
Parasympathetic Anatomy
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Once again, just 2 cells
Preganglionic (#1) cell body in either:
Brainstem
Spinal cord ---- S2 – S4
Craniosacral system
Parasympathetic Anatomy
Craniosacral
Parasympathetic Anatomy
• Synapse of preganglionic with ganglionic
neurons happens in the ganglion
• Ganglia are located on the target organs
Parasympathetic Anatomy
Craniosacral
Parasympathetic Anatomy
• Ganglionic axons are relatively short
• Synapse at target cell or organ
• Neurotransmitter is acetylcholine (ACh)
Parasympathetic Anatomy
Craniosacral
Summary
FIGURE 17-2
p. 445
Summary
• Sympathetic
1. Thoracolumbar
2. Paravertebral
ganglia
3. ACh then NE
• Parasympathetic
1. Craniosacral
2. Ganglia at target
3. ACh and ACh
Biological Effects
• Most organs have dual innervation
1. CV
• S – increase heart rate, force of ventricle
contraction, increase blood pressure by
constricting smooth muscles of arteries
• P -- opposite
Biological Effects
2. Respiration
• S – dilation of bronchiole smooth muscle
which increases diameter
• P – opposite
3. Digestion
• S – decreases activity of organs and
glands
• P -- opposite
Biological Effects
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Vision
S – dilation of pupil
P – constriction of pupil
Reprodction
S – causes ejaculation in males
P – sexual arousal (erection) in both
sexes