The PNS is composed of the groups of neurons (ganglia) and bundles of axons (nerves) that are outside of the brain and spinal cord. Ganglia are of two types, sensory or autonomic. Sensory ganglia contain unipolar sensory neurons and are found on the dorsal root of all spinal nerves as well as associated with many of the cranial nerves. Autonomic ganglia are in the sympathetic chain, the associated paravertebral or prevertebral ganglia, or in terminal ganglia near or within the organs controlled by the autonomic nervous system.
Nerves are classified as cranial nerves or spinal nerves on the basis of their connection to the brain or spinal cord, respectively. The twelve cranial nerves can be strictly sensory in function, strictly motor in function, or a combination of the two functions. Sensory fibers are axons of sensory ganglia that carry sensory information into the brain and target sensory nuclei. Motor fibers are axons of motor neurons in motor nuclei of the brain stem and target skeletal muscles of the head and neck. Spinal nerves are all mixed nerves with both sensory and motor fibers. Spinal nerves emerge from the spinal cord and reorganize through plexuses, which then give rise to systemic nerves. Thoracic spinal nerves are not part of any plexus, but give rise to the intercostal nerves directly.
abducens nerve
sixth cranial nerve; responsible for contraction of one of the extraocular muscles
axillary nerve
systemic nerve of the arm that arises from the brachial plexus
brachial plexus
nerve plexus associated with the lower cervical spinal nerves and first thoracic spinal nerve
cervical plexus
nerve plexus associated with the upper cervical spinal nerves
cranial nerve
one of twelve nerves connected to the brain that are responsible for sensory or motor functions of the head and neck
cranial nerve ganglion
sensory ganglion of cranial nerves
dorsal (posterior) root ganglion
sensory ganglion attached to the posterior nerve root of a spinal nerve
endoneurium
innermost layer of connective tissue that surrounds individual axons within a nerve
enteric nervous system
peripheral structures, namely ganglia and nerves, that are incorporated into the digestive system organs
enteric plexus
neuronal plexus in the wall of the intestines, which is part of the enteric nervous system
epineurium
outermost layer of connective tissue that surrounds an entire nerve
esophageal plexus
neuronal plexus in the wall of the esophagus that is part of the enteric nervous system
extraocular muscles
six skeletal muscles that control eye movement within the orbit
facial nerve
seventh cranial nerve; responsible for contraction of the facial muscles and for part of the sense of taste, as well as causing saliva production
fascicle
small bundles of nerve or muscle fibers enclosed by connective tissue
femoral nerve
systemic nerve of the anterior leg that arises from the lumbar plexus
fibular nerve
systemic nerve of the posterior leg that begins as part of the sciatic nerve
gastric plexuses
neuronal networks in the wall of the stomach that are part of the enteric nervous system
glossopharyngeal nerve
ninth cranial nerve; responsible for contraction of muscles in the tongue and throat and for part of the sense of taste, as well as causing saliva production
hypoglossal nerve
twelfth cranial nerve; responsible for contraction of muscles of the tongue
intercostal nerve
systemic nerve in the thoracic cavity that is found between two ribs
lumbar plexus
nerve plexus associated with the lumbar spinal nerves
median nerve
systemic nerve of the arm, located between the ulnar and radial nerves
nerve plexus
network of nerves without neuronal cell bodies included
oculomotor nerve
third cranial nerve; responsible for contraction of four of the extraocular muscles, the muscle in the upper eyelid, and pupillary constriction
olfactory nerve
first cranial nerve; responsible for the sense of smell
optic nerve
second cranial nerve; responsible for visual sensation
paravertebral ganglia
autonomic ganglia superior to the sympathetic chain ganglia
perineurium
layer of connective tissue surrounding fascicles within a nerve
phrenic nerve
systemic nerve from the cervical plexus that enervates the diaphragm
plexus
network of nerves or nervous tissue
prevertebral ganglia
autonomic ganglia that are anterior to the vertebral column and functionally related to the sympathetic chain ganglia
radial nerve
systemic nerve of the arm, the distal component of which is located near the radial bone
sacral plexus
nerve plexus associated with the lower lumbar and sacral spinal nerves
saphenous nerve
systemic nerve of the lower anterior leg that is a branch from the femoral nerve
sciatic nerve
systemic nerve from the sacral plexus that is a combination of the tibial and fibular nerves and extends across the hip joint and gluteal region into the upper posterior leg
sciatica
painful condition resulting from inflammation or compression of the sciatic nerve or any of the spinal nerves that contribute to it
spinal accessory nerve
eleventh cranial nerve; responsible for contraction of neck muscles
spinal nerve
one of 31 nerves connected to the spinal cord
sympathetic chain ganglia
autonomic ganglia in a chain along the anterolateral aspect of the vertebral column that are responsible for contributing to homeostatic mechanisms of the autonomic nervous system
systemic nerve
nerve in the periphery distal to a nerve plexus or spinal nerve
terminal ganglion
autonomic ganglia that are near or within the walls of organs that are responsible for contributing to homeostatic mechanisms of the autonomic nervous system
tibial nerve
systemic nerve of the posterior leg that begins as part of the sciatic nerve
trigeminal ganglion
sensory ganglion that contributes sensory fibers to the trigeminal nerve
trigeminal nerve
fifth cranial nerve; responsible for cutaneous sensation of the face and contraction of the muscles of mastication
trochlear nerve
fourth cranial nerve; responsible for contraction of one of the extraocular muscles
ulnar nerve
systemic nerve of the arm located close to the ulna, a bone of the forearm
vagus nerve
tenth cranial nerve; responsible for the autonomic control of organs in the thoracic and upper abdominal cavities
vestibulocochlear nerve
eighth cranial nerve; responsible for the sensations of hearing and balance
[link] To what structures in a skeletal muscle are the endoneurium, perineurium, and epineurium comparable?
[link] The endoneurium surrounding individual nerve fibers is comparable to the endomysium surrounding myofibrils, the perineurium bundling axons into fascicles is comparable to the perimysium bundling muscle fibers into fascicles, and the epineurium surrounding the whole nerve is comparable to the epimysium surrounding the muscle.
Visit this site to read about a man who wakes with a headache and a loss of vision. His regular doctor sent him to an ophthalmologist to address the vision loss. The ophthalmologist recognizes a greater problem and immediately sends him to the emergency room. Once there, the patient undergoes a large battery of tests, but a definite cause cannot be found. A specialist recognizes the problem as meningitis, but the question is what caused it originally. How can that be cured? The loss of vision comes from swelling around the optic nerve, which probably presented as a bulge on the inside of the eye. Why is swelling related to meningitis going to push on the optic nerve?
The optic nerve enters the CNS in its projection from the eyes in the periphery, which means that it crosses through the meninges. Meningitis will include swelling of those protective layers of the CNS, resulting in pressure on the optic nerve, which can compromise vision.
1. What type of ganglion contains neurons that control homeostatic mechanisms of the body?
A) sensory ganglion
B) dorsal root ganglion
C) autonomic ganglion
D) cranial nerve ganglion
C
2. Which ganglion is responsible for cutaneous sensations of the face?
A) otic ganglion
B) vestibular ganglion
C) geniculate ganglion
D) trigeminal ganglion
D
3. What is the name for a bundle of axons within a nerve?
A) fascicle
B) tract
C) nerve root
D) epineurium
A
4. Which cranial nerve does not control functions in the head and neck?
A) olfactory
B) trochlear
C) glossopharyngeal
D) vagus
D
5. Which of these structures is not under direct control of the peripheral nervous system?
A) trigeminal ganglion
B) gastric plexus
C) sympathetic chain ganglia
D) cervical plexus
B
1. Why are ganglia and nerves not surrounded by protective structures like the meninges of the CNS?
The peripheral nervous tissues are out in the body, sometimes part of other organ systems. There is not a privileged blood supply like there is to the brain and spinal cord, so peripheral nervous tissues do not need the same sort of protections.
2. Testing for neurological function involves a series of tests of functions associated with the cranial nerves. What functions, and therefore which nerves, are being tested by asking a patient to follow the tip of a pen with their eyes?
The contraction of extraocular muscles is being tested, which is the function of the oculomotor, trochlear, and abducens nerves.