Download 6-2 Cranial and Spinal Nerves

Cranial and Spinal Nerves
Suzanne D'Anna
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Cranial Nerves
emerge from the brain
 emerge through holes in the cranium
- cranial foramina
 12 pairs of cranial nerves
 Contains:
- sensory fibers (afferent)
- motor fibers (efferent)
- both sensory and motor fibers

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Cranial Nerves
I
II
III
IV
V
VI
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Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
VII
VIII
IX
X
XI
XII
(cont.)
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Accessory
Hypoglosseal
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I Olfactory
sensory nerve
 Function:
- smell (olfactory bulbs)

anosmia - loss of sense of smell
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II Optic
sensory nerve
 Function:
- vision (retina)

anopsia - defective vision
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III Oculomotor
mixed nerve (primarily motor)
 Functions:
- eyeball movement (4 eyeball muscles
and 1 eyelid muscle)
- lens accommodation
- pupil constriction
- muscle proprioception

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III Oculomotor

(cont.)
Injury or lesion may cause:
- strabismus - squinting
- ptosis - drooping of upper eye lid
- diplopia - loss of accommodation for
near vision and double vision
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IV Trochlear
mixed nerve (primarily motor)
 Functions:
- eyeball movement (superior oblique
muscles)
- muscle proprioception

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V Trigeminal
mixed nerve
 Functions:
- sensations ( face, scalp, teeth, lips,
eyeballs, nose and throat lining)
- general sensations from the tongue
- proprioception (face and scalp)
- chewing (muscles of mastication)

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VI Abducens
mixed nerve (primarily motor)
 Functions:
- eyeball movement (lateral rectus
muscle)
- muscle proprioception

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VII Facial
mixed nerve
 Functions:
- taste (anterior 2/3 of tongue)
- proprioception (face and scalp)
- facial expression (muscles of the face)
 Injury:
Bell’s palsy - loss of taste, inability to close
eyes

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VIII Vestibulocochlear
sensory nerve
 Functions:
- balance (vestibular apparatus of the
internal ear)
- hearing (cochlea of internal ear)

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VIII Vestibulocochlear

(cont.)
Injury may cause:
- tinnitus - ringing of the ear or
deafness
- vertigo - feeling of rotation, dizziness
- ataxia and nystagmus - involuntary
rapid movement of the eyeball
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IX Glossopharyngeal
mixed nerve
 Functions:
- taste (posterior 1/3 of the tongue)
- proprioception for swallowing (throat
muscles)
- blood pressure receptors (carotid
sinuses)

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X Vagus
mixed nerve
 Functions:
- chemoreceptors (blood oxygen
concentration, aortic bodies)
- pain receptors (respiratory and digestive
tracts)
- sensations (external ear, larynx, and
pharynx)
- taste (tongue)
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
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X Vagus

(cont.)
Functions:
- heart rate and stroke volume
(pacemaker and ventricular muscles)
- peristalsis (smooth muscles of the
digestive tract)
- airflow (smooth muscles in bronchial
tubes)
- speech and swallowing (muscles of
larynx and pharynx)
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XI Accessory
mixed nerve (primarily motor)
 Function:
- head rotation (trapezius and
sternocleidomastoid muscles

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XII Hypoglosseal
mixed nerve (primarily motor)
 Functions:
- speech and swallowing (tongue and
throat muscles)

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Classification of Spinal Nerves
all emerge from spinal cord
 emerge through holes formed by notches
on adjoining vertebrae
 31 pairs
 all mixed nerves (containing both sensory
and motor)
 named and numbered according to region
and level of spinal cord from which they
emerge

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Classification of Spinal Nerves
(cont.)

8 pairs of cervical nerves
- first cervical pair emerges between
atlas (first cervical vertebra) and
occipital bone
- first 7 emerge above vertebra of the
same number
- 8th emerges between 7th cervical
vertebra and 1st thoracic vertebra
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Classification of Spinal Nerves
(cont.)
12 pairs of thoracic nerves
 5 pairs of lumbar nerves
 5 pairs of sacral nerves
 1 pair of coccygeal nerves
- all emerge below vertebra of the same
number
- emerge through intervertebral foramina

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Plexuses
(plexus = braid)
network of adjacent nerves
cervical plexus:
 brachial plexus:
 lumbar plexus:
 sacral plexus:

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C1 - C5
C5 - T1
L1 - L4
L4 - S4
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Brachial Plexus
C4
C5
C6
C7
C8
T1
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Lumbo-Sacral Plexus
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Dermatomes
specific segment of skin which each
spinal nerve innervates
 knowledge can help physician
determine which segment of the spinal
cord or which spinal nerve is affected

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