Fundamentals of Anatomy and Physiology

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

2. The peripheral nervous system (PNS) consists
   of the afferent peripheral system (sensory neurons) and
   the efferent peripheral system (motor neurons).

Introduction.

1. The nervous system is the body’s control center and
   communication network.^


2. It shares in the maintenance of homeostasis with
   the endocrine system.

General Organization

1. 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.