cranial nerves and spinal nerves

1. ivyanatomy.com
section 5, chapter 11
Cranial and Spinal Nerves

2. Peripheral Nervous System
The PNS consists of
12 pairs of Cranial nerves arising from the brain
31 pairs of Spinal nerves arising from the spinal cord
Sensory fibers relay information from receptors to CNS
Somatic (voluntary) fibers connecting to the skin and skeletal muscles
Autonomic fibers connecting to viscera (involuntary)
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3. Structure of a
Peripheral Nerve
Peripheral nerves consist of
bundles of nerve fibers encased
by connective tissue.
Fasicle – organized bundle
of nerve fibers.
Connective Tissue Coverings
1.Epineurium – outermost layer
2.Perineurium – Surrounds fasicles
3.Endoneurium –
surrounds individual nerve fibers

4. Structure of a Peripheral Nerve
Blood vessels pass through perineurium and epineurium. Capillaries
within endoneurium provide oxygen and nutrients to the neurons.
Figure 11.24. Scanning electron micrograph of a peripheral
nerve. Nerve fibers are organized into bundles, called fascicles.

5. Nerve and Nerve Fiber
Classification
• Sensory nerves - conduct impulses into brain or spinal cord
• Motor nerves - 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)
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6. Cranial Nerves (CN) I - IV
Olfactory nerves (CN I) transmit impulses
associated with smell
Optic nerves (CN II) transmit impulses associated
with vision
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 (superior oblique)
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7. Cranial Nerve V
Trigeminal nerve (CN V) - 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

8. 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 and 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.

9. Cranial Nerves VIII and IX
Vestibulocochlear nerve (CN VIII)
Vestibular branch - Sensory from equilibrium
receptors of ear
Cochlear branch - Sensory from hearing receptors
Glossopharyngeal nerve (CN IX)
Sensory of tongue - taste
Motor to salivary glands
Motor to pharynx - swallowing
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10. Cranial Nerve X
• Vagus nerve (CN X) “Wandering”
Mixed nerve
• Somatic motor to muscles of
speech and swallowing
• 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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

11. 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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12. Cranial Nerves
The 12 pairs of cranial nerves
I. Olfactory
II. Optic
III. Oculomotar
IV. Trochlear
V. Trigeminal
VI. Abducens
VII. Facial
VIII.Vestibulocochlear
IX. Glossopharyngeal
X. Vagus
XI. Accessory
XII. Hypoglossal
Pneumonic Device for remembring the
12 pairs of cranial nerves
I. Oh
II. Once
III. One
IV. Takes
V. The
VI. Anatomy
VII. Final
VIII.Very
IX. Good
X. Vacations
XI. Are
XII. Heavenly

13. Cranial Nerves

14. 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)

15. Nerve Plexuses
A Nerve plexus is a complex network formed by anterior branches of spinal nerves
• The fibers of various spinal nerves are sorted and recombined
• There are three (3) nerve plexuses:
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)

16. Brachial Plexus
(2) Brachial plexus
Formed by C5-T1 spinal nerves
Lies deep within shoulders
Branches include:
1. Radial Nerve
• extensor muscles of forearm, wrist, and fingers
• 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
Figure 11.33 Nerves of the brachial plexus

17. 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.

18. Thoracic Spinal Nerves
The thoracic spinal nerves give rise to
intercostal nerves
• Supply intercostal muscles
• Supply muscles of upper abdominal
wall
• Receive sensory from skin of the
thorax and abdomen
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.
End of section 5,
chapter 11