chapter 011

The Human Body in Health and Illness, 4th edition

Barbara Herlihy

Chapter 11:Nervous System: Spinal Cord and

Peripheral Nerves

Lesson 11-1 Objectives

• Describe the anatomy of the spinal cord and list its three functions.

• List five components of the reflex arc.

Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights

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Spinal Cord Structure

• Continuation of the brain stem

• Tubelike structure located in the spinal cavity

• Extends from foramen magnum to L1

• Diameter similar to the thickness of the thumb


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Lumbar Puncture

• CSF withdrawn from subarachnoid space between L3 and L4


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Spinal Cord Cross Section

• Gray matter– Inner H zone– Central canal

• White matter– Location of tracts


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Spinal Cord Tracts

Ascending: Sensory• Spinothalamic: Pain

pathway• Dorsal column• Spinocerebellar

Descending: Motor• Pyramidal: Major motor

tract• Extrapyramidal


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Spinal Cord Injuries


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Nerve Attachment to Spinal Cord


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Spinal Cord Function

• Sensory pathway• Motor pathway• Reflex center


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Reflex Arc: Five Components

• Receptor• Afferent neuron• Integrating

center• Efferent neuron• Effector organ


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Examples of Reflexes


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Lesson 11-2 Objectives

• List and describe the functions of the 12 pairs of cranial nerves.

• Identify the classification of spinal nerves.• List the functions of the three major plexuses.


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Nerve vs. Neuron

• Neuron: A single nerve cell

• Nerve: Bundles of neurons with fascia and blood supply


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Peripheral Nerves: Two Classification Systems

• Structural classification: Origin of the fiber– Cranial nerves– Spinal nerves

• Functional classification: Where nerves go and what they do– Somatic afferent nerves– Somatic efferent nerves– Autonomic nervous system (ANS)


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Cranial Nerves

• 12 pairs• Classification:

Sensory, motor, mixed

• Naming system: CN + Roman numeral (CN IV, CN V, CN X)


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Cranial Nerves (cont’d.)

• CN I: Olfactory nerve (smell)• CN II: Optic nerve (sight)• CN III: Oculomotor (most movements of

eyeball, eyelid, and pupil size)• CN IV: Trochlear (movement of eyeball)


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Cranial Nerves (cont’d.)• CN V: Trigeminal (chewing; sensations in face,

scalp, cornea, teeth)– Sensory arm of corneal reflex– Trigeminal neuralgia

• CN VI: Abducens (eyeball movement)• CN VII: Facial nerve (facial expression,

salivation, taste, tearing, and blinking)– Motor arm of corneal reflex– Bell’s palsy


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• CN VIII: Vestibulocochlear (hearing, balance)– Vestibular branch—balance– Cochlear branch—hearing– CN IX: Glossopharyngeal (swallowing, secretion of

saliva; taste)• Gag and blood pressure reflexes


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• CN X: Vagus (“wanderer” nerve) innervates many thoracic and abdominal organs and voice box; sensory arm of baroreceptor reflex

• CN XI: Accessory (head movement and shrugging shoulders, swallowing)

• CN XII: Hypoglossal (speech and swallowing)


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Spinal Nerves: 31 Pairs

• Cervical—8• Thoracic—12• Lumbar—5• Sacral—5• Coccygeal—1• Cauda equina


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Spinal Nerve: Plexuses

• Cervical – C1 to C4

• Brachial – C5 to C8, T1

• Lumbosacral – T12, L1-L5, S1-S4


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Some Important Spinal Nerves• From cervical plexus

– Phrenic

• From brachial plexus– Axillary– Radial, ulnar, median

• From lumbosacral– Femoral, obturator,

sciatic, tibial, common peroneal


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Examples of Nerve Involvement


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Dermatome• Area of skin

innervated by a spinal nerve

• Each named for the nerve serving it

• Used diagnostically to determine location of nerve damage


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chapter 011

Health & Medicine

imprint of elsevier

peripheral nerves

spinal cord injuriescopyright

pairs of cranial nerves

spinal cavity

spinal cordcopyright

cn x copyright

spinal cord tracts ascending