C h a p t e r 3 4
Organization and Control of Neural Function
849
sympathetic nervous system often is referred to as the
thoracolumbar division of the ANS. These pregangli-
onic neurons have axons that are largely myelinated and
relatively short. The postganglionic neurons of the sym-
pathetic nervous system are located in the paravertebral
ganglia of the sympathetic chain that lie on either side
of the vertebral column, or in prevertebral sympathetic
ganglia such as the celiac ganglia, the branches of which
innervate the liver, stomach, and other visceral organs
(Fig. 34-23). Besides postganglionic efferent neurons,
the sympathetic ganglia contain interconnecting neurons
similar to those associated with complex circuitry in the
brain and spinal cord, many of which inhibit modulate
preganglionic-to-postganglionic transmission.
TABLE 34-3
Characteristics of the Sympathetic and Parasympathetic Nervous Systems
Characteristic
Sympathetic Outflow
Parasympathetic Outflow
Location of preganglionic cell bodies T1–T12, L1 and L2
Cranial nerves: III, VII, IX, X; S2 to S4
Relative length of preganglionic fibers Short—to paravertebral chain of ganglia or
to aortic prevertebral of ganglia
Long—to ganglion cells near or in the
innervated organ
General function
Catabolic—mobilizes resources in
anticipation of challenge for survival
(preparation for “fight-or-flight” response)
Anabolic—concerned with
conservation, renewal, and storage
of resources
Nature of peripheral response
Generalized
Localized
Neurotransmitter at ganglion
ACh
ACh
Receptor at ganglion
Transmitter of postganglionic neuron
Type of transmitter receptors at target
synapse
Target effectors
Nicotinic (N
N
)
NE (most synapses)*
NE and Epi (secreted by adrenal gland)
Alpha (
α
) and Beta (
β
)
Smooth muscle, cardiac muscle, and
secretory cells throughout body
Nicotinic (N
N
)
ACh
Muscarinic (M)
Most viscera of the head and the
thoracic, abdominal, and pelvic cavities
Ach, acetylcholine; NE, norepinephrine; Epi, epinephrine
*Postganglionic sympathetic nerve fibers to sweat glands, piloerector muscles, and a few blood vessels are
cholinergic.
To head (e.g., pupillary muscles)
and carotid arteries with periarterial plexus
Spinal nerves to
effector organs in body
wall and limbs
To stomach and
other abdominal
viscera
To lower limbs
Below L2
Above T1
Spinal cord
Intermedio-
lateral horn
Ventral horn
Spinal
nerve
Ventral
root
Sympathetic trunk (chain)
with paravertebral ganglia
Ventral and
dorsal rami
Gray ramus
communicans
White ramus
communicans
Prevertebral
ganglion
Synapse
Splanchnic
nerves
FIGURE 34-23.
Sympathetic
pathways. Sympathetic
preganglionic fibers (blue) leave
the spinal cord by way of the
ventral root of the spinal nerves,
enter the ventral primary rami, and
pass through the white rami to the
prevertebral or paravertebral ganglia
of the sympathetic chain, where
they synapse with postganglionic
neurons (black). Other preganglionic
neurons (red dotted lines) travel
directly to their destination in the
various effector organs.
