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Ch.14 PNS Outline
I.
All nervous system outside brain & sp. Cord
1.
Nerves (afferent & efferent)
a.
2.
3.
II.
Spinal & Cranial
Ganglia – nerve cell bodies
a.
Afferent (sensory)
b.
Efferent (motor)
Sensory receptors
Spinal Nerves (Fig. 14-1)
A.
31 pairs
B.
Thousands of nerve fibers in each
C.
All mixed
D.
Names (Fig. 14-1) – according to level of v. column at which they emerge
from:
1.
Cervical nerves – C1-C8 (8 pairs)
2.
Thoracic nerves (12 pairs)
3.
Lumbar nerves (5 pairs)
4.
Sacral nerves (5 pairs)
5.
Coccygeal nerves (1 pair)
E.
C1-C7 exit intervertebral foramen above named vertebrae
F.
C8 – exits b/t C7 & T1
G.
All other exit inferior to named vertebrae
H.
Cauda Equina – lumbar & sacral nerves in v. canal
I.
Structure of spinal nerves
1.
Roots (Fig. 14-2)
a.
Ventral (anterior) root (includes motor fibers)
b.
Dorsal (posterior) root (includes sensory fibers)
1)
Dorsal root ganglion (spinal ganglion)
2.
Roots & ganglia lay w/in spinal cavity
3.
Spinal nerve rami (Fig. 14-2) – branches off spinal nerve after
exiting foramen
a.
Dorsal ramus
1
b.
c.
J.
1)
Supplies somatic motor & sensory fibers to smaller
nerves
2)
Muscles & skin of posterior head, neck, trunk
Ventral ramus
1)
Motor & sensory fibers to anterior & lateral trunk &
extremities
2)
Form plexuses
Sympathetic ramus
1)
Autonomic nervous fibers split from ventral rami
2)
Join ganglia of sympathetic chain
3)
There, some continue to autonomic effectors via
splanchnic nerves
4)
Others join back to ventral ramus
Nerve plexuses (p. 415)
1.
Plexus - ventral rami subdivide and join to one another to form
individual nerves
a.
All but T2-T12
2.
Each muscle in limb receives its nerve supply from more than one
spinal nerve root
3.
Damage in one root does not affect all muscles of limb
2
4.
Four main pairs of plexuses (Fig. 14-1; Table 14.1)
a.
b.
c.
d.
e.
K.
Cervical plexus (Fig. 14-3; Table 14-1)
1)
Under sternocleidomastoid
2)
ventral rami C1 - C4, plus part of C5 & cranial
nerves XI and XII
3)
Major nerve: phrenic nerve
Brachial plexus (Fig. 14-4; Table 14-1)
1)
C5 through T1
2)
Innervates lower shoulder & all of the arm
Lumbar plexus (Fig. 14-5; Table
14-1)
1)
L1 - L4
2)
Innervates the thigh and leg
3)
Femoral nerve most important
Sacral plexus (Fig. 14-5;Table 14-1)
1)
L4 through S4
2)
Innervates the thigh and leg
3)
Tibial nerve and common peroneal nerve join to
form the sciatic nerve
Coccygeal plexus (small plexus) (Fig.14-5; Table 14-1)
1)
S5 plus part of S4, along with the
coccygeal nerve
2)
Innervates the floor of the pelvic
cavity
Dermatomes & myotomes (p. 418)
1.
2.
Dermatome (Figs. 14-6, 14-7)
a.
“skin section” – body map of sensory nerves
b.
each skin surface area supplied by sensory fibers of a given
sp nerve
Myotome (Figs. 14-6, 14-8)
a.
sk muscle or grps of
muscles that receive motor
axons from a given spinal
nerve
3
III.
IV.
Cranial Nerves (12 pairs) (Fig. 14-9)
A.
Types of axons in a cranial nerve (CN): sensory, motor, mixed (Table 142)
B.
Olfactory nerve—CN I (Fig. 14-9; Table 14-3)
C.
Optic nerve—CN II (Fig. 14-9; Table 14-3)
D.
Oculomotor nerve—CN III (Fig.14-9; Table 14-)
E.
Trochlear nerve—CN IV (Fig. 14-9; Table 14-3)
F.
Trigeminal nerve—CN V (Figs. 14-9, 4-10; Table 14-3)
G.
Abducens nerve—CN VI (Fig. 14-9; Table 14-3)
H.
Facial nerve—CN VII (Figs. 14-9, 14-11; Table 14-3)
I.
Vestibulocochlear nerve—CN VIII (Fig. 14-9; Table 14-3)
J.
Glossopharyngeal nerve—CN IX (Figs. 14-9, 14-12; Table 14-3)
K.
Vagus nerve—CN X (Figs. 14-9, 14-13; Table 14-3)
L.
Accessory nerve—CN XI (Figs.14-9, 14-14; Table 14-3
M.
Hypoglossal nerve—CN XII (Fig. 14-9; Table 14-3)
Divisions of the Peripheral Nervous System (p. 429)
A.
Divisions
1.
Sensory (afferent) division (Chapter 15)
2.
Motor (efferent) division
a.
Somatic motor nervous system
b.
Efferent autonomic nervous system
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B.
Somatic motor nervous system
1.
C.
Basic principles of somatic motor pathways
a.
Anterior horn neuron stimulates skeletal muscles (somatic
effectors) with acetylcholine
b.
Each skeletal muscle motor unit involves a single motor
neuron from the anterior horn
Somatic reflexes (p. 429)
1.
2.
Nature of a reflex
a.
Cranial reflex
b.
Spinal reflex
c.
Somatic reflex (involves skeletal muscle)
d.
Autonomic reflex (involves smooth muscle, cardiac
muscle, or glands)
Somatic reflexes of clinical importance
a.
Knee jerk reflex (Fig. 14-15)
1)
b.
Two-neuron reflex arc
a)
Sensory neurons
b)
Reflex center (synapses)
c)
Motor neurons
Ankle jerk reflex
1)
Two-neuron reflex arc
c.
Babinski reflex
d.
Corneal reflex
e.
Abdominal reflex
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