Chapter 11, Section 5

Cranial and Spinal Nerves

• 12 pairs of Cranial nerves arising from the brain

• 31 pairs of Spinal nerves arising from the spinal cord

Peripheral Nervous System

•Sensory fibers relay information from receptors to CNS

• Somatic (voluntary) fibers connecting to the skin and skeletal muscles

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• Somatic (voluntary) fibers connecting to the skin and skeletal muscles

• Autonomic fibers connecting to viscera (involuntary)

Structure of a

Peripheral Nerve

Peripheral nerves consist of

bundles of nerve fibers encased

by connective tissue.

Fasicle – organized bundle

Connective Tissue Coverings

1. Epineurium – outermost layer

2. Perineurium – Surrounds fasicles

3. Endoneurium –

surrounds individual nerve fibers

Fasicle – organized bundle

of nerve fibers.

Blood vessels pass through perineurium and epineurium. Capillaries within

endoneurium provide oxygen and nutrients to the neurons.

Structure of a Peripheral Nerve

Figure 11.24. Scanning electron micrograph of a peripheral

nerve. Nerve fibers are organized into bundles, called fascicles.

Nerve and Nerve Fiber

Classification

• Sensory nerves

• Conduct impulses into brain or spinal cord

• Motor nerves

• Conduct impulses to muscles or glands

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• Conduct impulses to muscles or glands

• Mixed (both sensory and motor) nerves

• Contain both sensory nerve fibers and motor nerve fibers

• Most nerves are mixed nerves

• ALL spinal nerves are mixed nerves (except the first pair)

Cranial Nerves (CN) I - IV

• Olfactory nerve (CN I)

• Fibers transmit impulses

associated with smell

• Optic nerve (CN II)

• Fibers transmit impulses

associated with vision

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• Oculomotor nerve (CN III)

• Motor impulses to

muscles that move the

eyes, the eyelids, iris, and

the lens

• Trochlear nerve (CN IV)

• Motor impulses to

muscles that move the eyes

Cranial Nerve V

• Trigeminal nerve (CN V)

• “Three (3) twins”

• Motor to muscles of mastication

(chewing)

• 3 Branches

• Ophthalmic branch – sensory

around eyes

• Maxillary branch – sensory of

upper jaw & teeth

• Mandibular branch – sensory of

lower jaw & teeth

Cranial Nerves VI and VII

• Abducens nerve (CN VI)

• Motor impulses to lateral rectus

muscles of eye = eye movement

• Facial nerve (CN VII)

• Sensory from taste receptors• Sensory from taste receptors

• Motor to muscles of facial expression

Figure 11.27 the facial nerves are associated

with taste receptors on the tongue and with

muscles of facial expression.

Cranial Nerves VIII and IX

• Vestibulocochlear nerve (CN VIII)

• Aka auditory nerve

• Sensory nerve

•Two (2) branches:

• Vestibular branch

• Glossopharyngeal nerve (CN IX)

• Sensory of tongue - taste

• Motor to salivary glands

•Motor to pharynx - swallowing

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• Vestibular branch

• Sensory from equilibrium

receptors of ear

• Cochlear branch

• Sensory from hearing

receptors

Cranial Nerve X

• Vagus nerve (CN X)

• “Wandering”

• Mixed nerve

• Somatic motor to muscles of

speech and swallowing

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• Autonomic motor to viscera of

thorax and abdomen

• Sensory from pharynx, larynx,

esophagus, and viscera of thorax

and abdomen

Figure 11.28 the vagus nerves

extend from medulla downward

through thorax and abdomen to

supply many organs

Cranial Nerves XI and XII

• Accessory nerve (CN XI)

• Motor to muscles of soft palate,

pharynx and larynx

•Motor to muscles of neck and back

• Hypoglossal nerve (CN XII)

• Motor to muscles of the

tongue

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•Motor to muscles of neck and back

Cranial Nerves

I. Olfactory

II. Optic

III. Oculomotar

I. Oh

II. Once

III. One

Pneumonic Device for remembring the

12 pairs of cranial nerves

The 12 pairs of cranial nerves

III. Oculomotar

IV. Trochlear

V. Trigeminal

VI. Abducens

VII. Facial

VIII.Vestibulocochlear

IX. Glossopharyngeal

X. Vagus

XI. Accessory

XII. Hypoglossal

III. One

IV. Takes

V. The

VI. Anatomy

VII. Final

VIII.Very

IX. Good

X. Vacations

XI. Are

XII. Heavenly

Cranial Nerves

Spinal Nerves

• ALL are mixed nerves (except the first pair)

• 31 pairs of spinal nerves:

• 8 cervical nerves (C1 to C8)

• 12 thoracic nerves (T1 to T12)

• 5 lumbar nerves (L1 to L5)

• 5 sacral nerves (S1 to S5)

• 1 coccygeal nerve (Co or Cc)

Nerve Plexuses

• Nerve plexus

• Complex networks formed by anterior branches of spinal nerves

• The fibers of various spinal nerves are sorted and recombined

• There are three (3) nerve plexuses:

• (1) Cervical plexus

• Formed by anterior branches of C1-C4 spinal nerves

• Lies deep in the neck

• Supply to muscles and skin of the neck

• C3-C4-C5 nerve roots contribute to phrenic nerves bilaterally

Phrenic Nerves conduct motor impulses to the diaphragm

(C3,4, and 5 keep the diaphragm alive)

• (2) Brachial plexus

• Formed by C5-T1

• Lies deep within shoulders

• Branches include:

1. Radial Nerve

• extensor muscles of forearm, wrist, and fingers

•May be damaged with crutches

Brachial Plexus

•May be damaged with crutches

2. Ulnar Nerve

• Intrinsic muscles of hand

• Funny bone

3. Median Nerve

• Flexor muscles of forearm, wrist, and fingers

• Inflamed with carpal tunnel syndrome

Figure 11.33 Nerves of the brachial plexus

Lumbosacral Plexus

• (3) Lumbosacral plexus

• Formed by T12-S5

• Branches include:

1. Obturator nerve • Supply motor impulses to adductors of thighs

2. Femoral nerve• Supply motor impulses to muscles of anterior thigh

and sensory impulses from skin of thighs and legs

3. Sciatic nerve• Supply muscles and skin of thighs, legs and feet

Figure 11.34 Nerves of the lumbosacral plexus.

•The thoracic spinal nerves give rise to

intercostal nerves• Supply intercostal muscles

• Supply muscles of upper abdominal

wall

Thoracic Spinal

Nerves

Figure 11.32. The ventral branches of

spinal nerves give rise to three

plexuses. In the thoracic region spinal

nerves give rise to intercostal nerves.

• Receive sensory from skin of the

thorax and abdomen

End of Chapter 11, Section 5