Transcript Cranial Nerves

Cranial Nerves
 Originates from brain (mainly brain
stem) and passes through foramina
of skull
 There are 12 pairs of cranial nerves
 They have both name and number
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There are mixed cranial
nerves, sensory cranial nerves
and motor cranial nerves
All motor cranial nerves contain a
small number of sensory fibers
that is proprioceptive
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Olfactory nerve I
 The axons that makes
the olfactory nerve
starts from nasal
mucosa.
 They make 20 small
bundles of fibers that
pierce the cribriform
plate
 Olfactory nerve carry
the sense of smell
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Optic nerve II
 Axons start in retina
 They carry visual
information to brain.
 Most of the optic
tract fibers terminate
in thalamus.(lateral
geniculate nucleus)
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Occulomotor nerve III
 Starts from
occulomotor nucleus
in the ventral part of
the midbrain.
 Extends to various
external eye
muscles
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Trochlear nerve IV
 Originates from
the midbrain
 They go to the
superior oblique
muscle of the
eye
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Trigeminal nerve V
 It splits into three
large branches
 It makes ophtalmic
nerve, maxillary
nerve, mandibular
nerve
 Carry sensory
information from
face and teeth
 Its motor nerve
controls mastication
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Abducence nerve VI
 Its fibers originate from pons
and extends to the lateral rectus
muscle of the eye.
 This muscle abducts the eye.
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CN VI
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Facial nerve VII
 Arise from the lower part of the pons.
 Innervates superficial muscles of face
and skull.
 Its autonomic fibers innervate the
submaxillary and sublingual salivary
glands and lacrimal glands.
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Vestibulocochlear nerve
Has two distinct divisions:
Vestibular and cochlear
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Vestibular branch
 Arise from semicircular canals
in internal ear and terminates in
pons medulla and cerebellum.
 Its function is to maintain
equilibrium.
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Cochlear branch
 Starts from the organ of corti and
terminate between medulla and pons.
 Conduct the sense of hearing.
 Its some times called auditory or
acoustic nerve.
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Glossopharyngeal nerve IX
 It is a mixed nerve.
 Supplies the tongue and pharynx
 It also supplies the carotid sinus
 Its fibers extend to medulla.
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Vagus nerve X
 Contains sensory and motor fibers
 It has many widely distributed branches
 Sensory fibers supply, pharynx, larynx,
trachea, heart, carotid body, lungs,
bronchi, esophagus, stomach, small
intestine and gall bladder
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motor fibers of vagus nereve
 Are mainly autonomic.
 They controls muscles for swallowing
 Most of them are parasympathetic.
 They also go to pharynx, larynx,
thoracic organs and abdominal organs.
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Accessory nerve XI
Is a motor nerve
Is considered an
accessory nerve to vagus.
It was formerly called the
spinal accessory nerve
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Hypoglossal nerve XII
 The motor fibers supplies the
muscles of the tongue
 It also have sensory
(proprioceptive) nerves.
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Divisions of peripheral nervous system
Sensory division
Motor division
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Somatic motor nervous system
 Includes all the voluntary movements
outside the CNS
 The end motor neuron stimulates the
effector muscle by means of
acetylcholine
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Somatic reflexes
 A reflex is a predictable response to an
stimulus
 Based on the center of a reflex we have
cranial and spinal reflexes.
 We also have somatic reflexes and
autonomic reflexes
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Autonomic reflexes
 Is either muscle contraction or glandular
secretion
 Cause Smooth or cardiac muscle
contraction or secretion of a gland
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Important somatic reflexes
 Knee jerk reflex
 Ankle jerk reflex
 Babinski reflex
 Corneal reflex
 Abdominal reflex
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Knee jerk reflex
 Is extension of lower leg in response to
tapping patellar tendon
 It is also a spinal cord reflex, segmental
reflex, stretch reflex, extensor reflex and
deep tendon reflex.
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Ankle jerk reflex
 It is called achilles reflex
 Cause plantar flexion
 Its center is in the first and second
segment of the cord
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Babinski reflex
 Is extension of
great toe
 Infants show
this reflex up to
1 ½ yrs
 After that it is
considered
abnormal
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Corneal reflex
 Is blinking in response to touching the
cornea
 It is mediated by the ophtalmic branch
of fifth cranial nerve
 Centers in the pons and motors in
seventh cranial nerve
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Abdominal reflex
 Is drawing in of the abdominal wall in
response to stroking the side of the
abdomen
 Its center is in 9th to 12th spinal nerves
 In pregnancy it is abscent.
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