1. Cranial and Spinal Nerves
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Cranial and Spinal Nerves
ivyanatomy.com

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) 2

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 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) 5

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) 6

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 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 9

10. Cranial Nerve X Vagus nerve (CN X) “Wandering” Mixed nerve
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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 the vagus nerves extend from medulla downward through thorax and abdomen to supply many organs

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 11

12. Cranial Nerves The 12 pairs of cranial nerves
Pneumonic Device for remembring the 12 pairs of cranial nerves Oh
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Final VIII.Very
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Olfactory Optic Oculomotar Trochlear Trigeminal Abducens
VII. Facial VIII.Vestibulocochlear
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XI.
Glossopharyngeal Vagus
Accessory
XII. Hypoglossal

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 Figure 11.3 Nerves of the brachial plexus
Formed by C5-T1 spinal nerves Lies deep within shoulders
Branches include:
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 11.3 Nerves of the brachial plexus

17. Lumbosacral Plexus (3) Lumbosacral plexus Formed by T12-S5
Branches include:
Obturator nerve
Supply motor impulses to adductors of thighs
Femoral nerve
Supply motor impulses to muscles of anterior thigh and sensory impulses from skin of thighs and legs
Sciatic nerve
Supply muscles and skin of thighs, legs and feet
Figure 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
The ventral branches of spinal nerves give rise to three plexuses. In the thoracic region spinal nerves give rise to intercostal nerves.