SENSORY GANGLION
Figure 8­42
Downloaded
by
[Rutgers
University
130.219.8.11]
at
[04/08/15].
Copyright
©
McGraw-Hill
Global
Education
Holdings,
Collections of neurons in the peripheral nervous system are known as ganglia, in contrast to neuronal collections in
the central nervous system, which are called nuclei.
LLC.
There are two different types of ganglia in the peripheral nervous system: sensory ganglia and autonomic ganglia.
Not
The autonomic ganglia are further subdivided into sympathetic and parasympathetic ganglia, which have a similar-
to
ity of histologic structure. The dorsal root, or spinal ganglia, are examples of sensory ganglia and are located near
be
redistributed
the dorsal aspect of the spinal cord. In addition to physiologic differences, sensory and autonomic ganglia can be
contrasted morphologically mainly by the size and shape of their neurons and by the fact that synapses occur in
autonomic ganglia and are absent from sensory ganglia.
or
Afferent fibers from nerve terminals in the skin, skeletal muscle, tendon, or other structures enter the sensory
modified
ganglia, conducting the nerve impulse from the periphery. These fibers do not synapse in the ganglia but bifurcate
near their cell body and convey the impulse into the spinal cord through the dorsal root. Some of these axons make
in
synaptic contact with either interneurons in the lateral horn of the spinal cord or with the large motor neurons of
any
the ventral horn, thereby forming the reflex arc. Other axons from the dorsal root ganglia enter the spinal cord and
way
ascend to the brainstem.
without
The histologic features of sensory ganglia include the presence of relatively large, spherical pseudounipolar neuronal
cell bodies (arrowheads), attendant satellite cells, nerve fibers, and associated Schwann cells. The neuronal cell bod-
permission.
ies are usually arranged in clusters through which, and along side of which, pass the nerve fibers.
Even at the low magnification of this image, the locations of the neurons are clearly identified by the morphology of
their nuclei and densely stained nucleoli. The sensory ganglia are encapsulated by fibrous connective tissue that is
penetrated by afferent nerve fibers (arrow).
398

---