The Nervous System: Introduction, Spinal Cord, and Spinal Nerves 245
Cervical
Plexus C1–C4
Nerve supply to muscles of
the neck and shoulder. Includes
the phrenic nerve which
stimulates the diaphragm
Brachial Plexus
C5 – C8, T1
Axillary, radial, median,
musculocutaneous, and
ulnar nerves
Conus
medullaris^
Lumbar Plexus
T12, L1–L4
Femoral and
obturator nerves^
Cauda
Sacral Plexus L5, S1–S2 equina L4–
(^) Sciatic (largest
nerve in the body),
common peroneal,
and tibial nerve
C1C2 (^)
C3
C5C4
C6
C7C8 (^)
T1^
T2^
T3^
T4^
T5^
T6^
T7
(^) T8
T9^
T10^
T11^
T12^
L1^
L2^
L3^
L4^
L5^
S1^
S2
S4S3
S5
Cervical
spinal^
nerves
Thoracic
spinal
nerves
Lumbar
spinal
nerves
Sacral
spinal
nerves^
Coccyx
spinal ®
nerve Learning (1)
Cengage ©
Figure 10- 10 The names and emergent levels of the 31 spinal
nerves.
Summary Outline
- The peripheral nervous system (PNS) consists
of the afferent peripheral system (sensory neurons) and
the efferent peripheral system (motor neurons).
Introduction.
- The nervous system is the body’s control center and
communication network.^ - It shares in the maintenance of homeostasis with
the endocrine system.
General Organization
- The central nervous system (CNS) consists of the
brain and spinal cord.
3. The efferent peripheral system can be subdivided into
the somatic nervous system, which sends sig-nals to
skeletal muscles, and the autonomic nervous system
(ANS), which sends signals to cardiac and smooth
muscles and glands.^
4. The ANS has two divisions: the sympathetic
division,- which stimulates and speeds up activity,
and the parasympathetic division, which restores or
slows down certain activities but stimulates the
body’s vegetative activities.