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
1
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
2
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
3
4
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)
5
6
Occulomotor nerve III
 Starts from
occulomotor nucleus
in the ventral part of
the midbrain.
 Extends to various
external eye
muscles
7
8
Trochlear nerve IV
 Originates from
the midbrain
 They go to the
superior oblique
muscle of the
eye
9
10
11
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
12
13
Abducence nerve VI
 Its fibers originate from pons
and extends to the lateral rectus
muscle of the eye.
 This muscle abducts the eye.
14
CN VI
15
16
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.
17
18
19
Vestibulocochlear nerve
Has two distinct divisions:
Vestibular and cochlear
20
Vestibular branch
 Arise from semicircular canals
in internal ear and terminates in
pons medulla and cerebellum.
 Its function is to maintain
equilibrium.
21
22
23
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.
24
25
Glossopharyngeal nerve IX
 It is a mixed nerve.
 Supplies the tongue and pharynx
 It also supplies the carotid sinus
 Its fibers extend to medulla.
26
27
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
28
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.
29
30
31
Accessory nerve XI
Is a motor nerve
Is considered an
accessory nerve to vagus.
It was formerly called the
spinal accessory nerve
32
33
34
Hypoglossal nerve XII
 The motor fibers supplies the
muscles of the tongue
 It also have sensory
(proprioceptive) nerves.
35
36
Divisions of peripheral nervous system
Sensory division
Motor division
37
Somatic motor nervous system
 Includes all the voluntary movements
outside the CNS
 The end motor neuron stimulates the
effector muscle by means of
acetylcholine
38
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
39
Autonomic reflexes
 Is either muscle contraction or glandular
secretion
 Cause Smooth or cardiac muscle
contraction or secretion of a gland
40
Important somatic reflexes
 Knee jerk reflex
 Ankle jerk reflex
 Babinski reflex
 Corneal reflex
 Abdominal reflex
41
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.
42
43
Ankle jerk reflex
 It is called achilles reflex
 Cause plantar flexion
 Its center is in the first and second
segment of the cord
44
45
Babinski reflex
 Is extension of
great toe
 Infants show
this reflex up to
1 ½ yrs
 After that it is
considered
abnormal
46
47
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
48
49
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.
50
51