Comparison of the Sympathetic and Parasympathetic Divisions
of the Autonomic Nervous System |
| Feature |
Sympathetic Division |
Sacral Part of Parasympathetic Division |
Cranial Part of Parasympathetic Division |
| location of presynaptic nerve cell bodies |
intermediolateral cell column in the gray matter of spinal cord levels T1-L2 |
intermediate gray matter in spinal cord levels S2-S4 |
cranial nn. nuclei |
| axons exit the spinal cord through |
ventral roots |
ventral roots |
na |
| axons leave the spinal nerve through |
white rami communicans (spinal nerves T1-L2) |
pelvic splanchnic nerves (spinal nerves S2-S4) |
na |
| axons return to the spinal nerve for peripheral distribution through |
gray rami communicans (all vertebral levels) |
na |
na |
| postsynaptic nerve cell bodies are located in the |
paravertebral ganglia (sympathetic trunk) or prevertebral ganglia; medulla of suprarenal is considered a special postganglionic cell type |
terminal ganglia |
terminal ganglia |
| presynaptic axon length |
long |
long |
long; vagus n. has the longest presynaptic parasympathetic axons |
| postsynaptic axon length |
long (because they often travel on the surfaces of blood vessels to the organ to be innervated) |
short (because terminal ganglia are in or on the organ to be innervated) |
short (because terminal ganglia are in or on the organ to be innervated) |
| named nerves that carry postsynaptic axons |
branches of spinal nerves, perivascular plexuses which are named for the vessel (celiac, superior mesenteric, etc.) |
none (synapse occurs in or on the organ innervated) |
none (synapse occurs in or on the organ innervated) |
Definitions - Parts of the Sympathetic Nervous System |
| Nerve |
Source |
Branches |
Motor |
Sensory |
Notes |
| spinal n. |
formed at the point where the dorsal and ventral rootlets meet; it ends
where the dorsal and ventral primary rami diverge |
dorsal primary ramus; ventral primary ramus |
to skeletal mm.; some levels carry preganglionic sympathetic axons (T1-L2) |
general sense (touch, pressure, pain, heat, cold, etc.) from the entire
surface of the neck, trunk and extremities; visceral pain (via the white ramus
communicans and the sympathetic nervous system) |
located at the intervertebral foramen; there are 31 pairs of spinal nerves
- 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal |
| ventral primary ramus |
first branch off of the ventral side of the spinal nerve |
numerous |
to skeletal mm. of the neck, trunk and extremities; sympathetic innervation
to the skin |
general sense (touch, pressure, pain, heat, cold, etc.) to the skin of the
trunk (except the back) and extremities; visceral pain via the white rami of
the sympathetic nervous system (T1-L2) |
a mixed nerve containing both motor and sensory fibers |
| sympathetic chain ganglia |
preganglionic sympathetic fibers arrive via white rami communicantes of
ventral primary rami of spinal nerves T1-L2 |
postganglionic sympathetic fibers depart via gray rami communicantes to
all spinal nn.; internal & external carotid nn.; cervical cardiac brs.; thoracic
direct visceral brs.; greater, lesser & least thoracic splanchnic nn.; lumbar
splanchnic nn.; sacral splanchnic nn. |
dilator pupillae, vascular smooth muscle, arrector pili muscles, sweat glands,
suprarenal medulla, heart, lungs and gut |
pain from viscera |
located lateral to the vertebral bodies in the neck, thorax & abdominopelvic
cavity; the ganglia plus their interconnecting fibers are also known as the
sympathetic trunk; preganglionic cell bodies are located in the intermediolateral
gray matter of spinal cord levels T1-L2 |
| paravertebral ganglia |
preganglionic sympathetic fibers arrive via white rami communicantes of
ventral primary rami of spinal nerves T1-L2 |
postganglionic sympathetic fibers depart via gray rami communicantes to
all spinal nn.; internal & external carotid nn.; cervical cardiac brs.; thoracic
direct visceral brs.; greater, lesser & least thoracic splanchnic nn.; lumbar
splanchnic nn.; sacral splanchnic nn. |
dilator pupillae, vascular smooth muscle, arrector pili muscles, sweat glands,
suprarenal medulla, heart, lungs and gut |
pain from viscera |
located lateral to the vertebral bodies in the neck, thorax & abdominopelvic
cavity; the ganglia plus their interconnecting fibers are also known as the
sympathetic trunk; preganglionic cell bodies are located in the intermediolateral
gray matter of spinal cord levels T1-L2 |
| prevertebral ganglia |
splanchnic nn. |
plexuses to abdominal and pelvic viscera |
vascular smooth muscle of vessels that supply abdominopelvic viscera |
pain from abdominopelvic viscera |
also known as: preaortic ganglia, collateral ganglia; these ganglia include the celiac ganglion, aorticorenal
ganglion, superior mesenteric ganglion and inferior mesenteric ganglion; preganglionic
parasympathetic axons of vagal trunk origin pass through the preaortic ganglia
but do not synapse there |
| white ramus communicans |
cell bodies located in the lateral horn gray matter of spinal cord levels
T1-L2; |
none |
axons contained within white rami communicantes will synapse on postganglionic
cell bodies that will ultimately innervate the skin, viscera, glands, blood
vessels, etc. |
pain from viscera is carried back to the spinal cord through the white ramus
communicans |
white rami communicantes connect the sympathetic chain to spinal nerves
at vertebral levels T1-L2; carries preganglionic sympathetic axons |
| gray ramus communicans |
cell bodies located in the sympathetic chain ganglia |
none |
carries postganglionic sympathetic axons to the spinal nerve; spinal nerve
will carry those axons peripherally to the skin, blood vessels, etc. |
none |
gray rami communicantes connect the sympathetic chain to spinal nerves
at all vertebral levels |
