Anatomy 5.7b PNS_Esguerra

Anatomy 5.7b     

January
17,
2012
 Dr.
Esguerra


The Peripheral Nervous System


 OUTLINE  I.
Functional
Components
of
Peripheral
Nerves
 II.
Spinal
Cord,
Roots
&
Nerves
 III.
Structure
of
Spinal
Nerves
 IV.
Segmental
Innervation
 V.
Cranial
Nerves
 VI.
Brainstem
Rule
of
“4”
 


  Objectives: Please refer to Anatomy 5.7a  

Italicized text were directly lifted from the recording of Dr. Esguerra’s  lecture  Text in Times New Roman were lifted from our references

I. FUNCTIONAL COMPONENTS OF PERIPHERAL NERVES 

‐ Olfactory
and
gustatory
receptors
 ‐ Muscles
of
branchiomeric
origin
–
the
ones that are 

derived from branchial arches (ms of mastication, facial  ms, larynx, pharynx, etc.) 
   Table 1.2 Sensory/Motor + Somatic/Visceral 

 

SOMATIC  (Somatic Nervous  System) 

SENSORY
 (Afferents)


SOMATIC
SENSORY
 General
Somatic
 Afferent
(GSA)


MOTOR
 (Efferents)


SOMATIC
MOTOR
 General
Somatic
 Efferent
(GSE)


• Peripheral nerves is a collective term for the cranial and spinal

nerves

• Each particle nerve fiber can be distinguished to 3 sets of 

functions:    o Afferent (Sensory) vs. Efferent (Motor) 

 Sensory
(Afferent)
Nerve
 ‐ CNS:
(Pseudo‐)
Unipolar
neurons
conducting
impulses
 from
sensory
organs
to
the
CNS
 ‐ Bundles of nerve fibers of the posterior root that carry nervous impulses to the central nervous system ‐ The cell bodies of these nerve fibers are situated in a swelling on the posterior root called the posterior root ganglion  Motor
(Efferent)

 ‐ CNS:
Multipolar
neurons
conducting
impulses
from
the
 CNS
to
effector
organs
muscles
and
glands
 ‐ Arises from the anterior root of the spinal cord
 ‐ Consists of bundles of nerve fibers carrying nerve impulses away from the central nervous system 
 o Somatic vs. Visceral 

Note:  ‐ GVE – only AUTONOMIC   ‐ GVA – visceral reflexes    Table 1.3 Summaries of Functional Components 

Somatic
 General  Visceral


Table 1.1 Somatic vs Visceral 

ATTRIBUTE 

Embryological
 Origin
of
Tissue


Examples
of
 Adult
Tissue
 Perception


SOMATIC SYSTEM  “Body
 Wall”:Somatic
 
 (Parietal)
Mesoderm
 
 (Dermatome,
 Myotome)
 Derms
of
skin,
 skeletal
muscle,
 connective
tissues
 Conscious,
 Voluntary


VISCERAL SYSTEM  
 “Organs”
Splanchnic
 
 (Visceral)
 Mesoderm,
 Endoderm
 
 
 
 Glands,
Cardiac
 muscles,
smooth
 muscles
 Unconscious,
 Involuntary



 o General vs. Special 

 General:
All
functions
of
spinal
nerves
and
some
cranial
 nerves
with
similar
functions
  Special:
Those
with
specialized
functions
(e.g.
Some
cranial
 nerves
 ‐ Special
sense
organ
of
the
eye
and
the
ear


Somatic
 Special  Visceral


Afferent
(GSA)
(CN
 V,
VII,
IX,
X)
 Efferent
(GSE)
(CN
 III,
IV,
VI,
XII)
 Afferent
(GVA)
(CN
 VII,
IX,
X)
 Efferent
(GVE)
(CN
 III,
VII,
IX,
X)
 Afferent
(SSA)
(CN
II,
 VII)
 Afferent
(SVA)
(CN
I,
 VII,
IX,
X)
 Efferent
(SVE)
(CN
V,
 VII,
IX,
XI)


Note:   ‐ GSA
and GSE  somatic nervous system 
 ‐ GVA
and GVE  ANS 
 ‐ There
is no special somatic efferent
  

II. SPINAL CORD, ROOTS & NERVES  • Spinal nerve roots pass from the spinal cord to the level of their respective intervertebral foramina, where they unite to form a spinal nerve • Spinal nerve is formed with the joining of the two roots coming  out of the spinal cord – dorsal and ventral roots  • Mixture of motor and sensory fibers  • Anterior Ramus – Larger; supply the muscles and skin over the anterolateral body wall and all the muscles and skin of the limbs.  • Posterior Ramus – Smaller; supply the muscles and skin of the back 

Group
21
|
Grant,
Guadalupe,
Guevara
N,
Guevarra
M,
Guillermo
L,
Guillermo
M,
Gutierrez,
Hernandez,
Herradura 




VISCERAL  (Autonomic Nervous  System)  VISCERAL
SENSORY
 General
Visceral
 Afferent
(GVA)
 (ex. Distention of  bowels, blood presse)  VISCERAL
MOTOR
 General
Visceral
 Efferent
(GVE)
 (ex. Promotes motility  or secretion of  glands.) 

Page
1
of
6


• Ganglia
–
connected to the spinal cord by two rami (dorsal and  ventral) communicantes, May be divided into sensory ganglia of spinal nerves (posterior root ganglia) and cranial nerves and autonomic ganglia.  o 3
Cervical
 o 10‐11
Thoracic
 o 4
Lumbar
 o 4
Sacral
 o 1
Coccygeal

  14
White
Rami
Communicantes
(T1‐L2)
–
more distal than  the Gray ramus   31
Gray
Rami
Communicantes
  


o Disruption
of
sensory
neurons
(dorsal ramus):
back paresthesia  (but the ventral ramus is intact)
 o Disruption
of
motor
neurons
(dorsal ramus):
Paralysis of deep  back muscles  


IV. SEGMENTAL INNERVATION  • Peripheral
nerves:
multiple
spinal
nerves
from
different
cord
 levels
 • Plexus
formation:
mixing
of
nerves
from
different
cord
levels
by
 union
and
division
of
bundles
 


III. STRUCTURE OF SPINAL NERVES  • Somatic
Pathways
 o Mixed
Spinal
Nerve
 o Somatic
Sensations
  Touch,
pain,
temperature,
pressure
  Proprioception:
joints,
muscles
  Somatic
Motor
Activity:
Innervate
Skeletal
Muscle
  GSA – fiber in the DORSAL root
  GSE – fiber in the VENTRAL root
 
 • Dorsal
and
Ventral
Rami
 o Territory
of
Dorsal
Rami:
Everything
else
but
the
head
(which
is
 innervated
by
the
ventral
rami)
 


Figure 5.1 Schematic demarcation of dermatomes 

  Figure 3.1 Sections through the thoracic region of the spinal cord showing  examples of nerve fibers entering or leaving the central nervous system;  ascending and descending nerve fibers (tracts or pathways) are also shown.   

 IMPACT
OF
LESIONS
 o Disruption
of
sensory
(afferent)
neurons:
Paresthesia (loss of  sensation)
 o Disruption
of
motor
(efferent)
neurons:
Paralysis (problem in  the roots) 
 o Disruption
of
both
sensory
and
motor
neurons:
Paresthesia &  Paraylsis









 • DERMATOMES
 o Single
spinal
nerve
 o Cutaneous
(skin)
sensory
territory
of
a
single
spinal
nerve
 o Dermatome
maps
  Based
on
clinical
findings
of
deficits
in
cutaneous
sensation
 –
one can localized the area of pain 
  Diagnostic
aids:
localization
of
lesions
to
cord
levels
  Limits
to
specificity
due
to
overlap
of
dermatomes
  Does not coincide with the actual peripheral nerve because  of the plexus they have 
 • MYOTOMES
 o Mass
of
muscle
innervated
by
a
single
spinal
nerve
 o NOT by location but by distribution
 o Myotome
maps
  Particular
functions
are
linked
to
muscle
innervated
by
 particular
cord
levels
  Example:
C5
lesion



Group
21
|Grant,
Guadalupe,
Guevara
N,
Guevarra
M,
Guillermo
L,
Guillermo
M,
Gutierrez,
Hernandez,
Herradura

 

Page
2
of
6
 


‐ Weakness
in
flexion
of
elbow
&
shoulder
 ‐ Weakness
in
abduction
&
lateral
rotation
of
shoulder





o SVA
–
visceral
sensation
of
taste
and
smell
 o SSA
–
somatic
sensations
of
vision,
hearing
and
equilibrium


o Distribution
of
a
single
spinal
root
throughout
a
plexus
 o Myotome
–
return
to
the
C5
lesion
example
  Abduction:
supraspinatus
&
deltoid
  Lateral
Rotation:
infraspinatus
&
teres
minor
  Fexion:
biceps
brachii
&
brachalis


V. CRANIAL NERVES  • 12
Cranial
Nerves
 o Olfactory
(I)
 o Optic
(II)
 o Oculomotor
(III)
 o Trochlear
(IV)
 o Trigeminal
(V)
 o Abducens
(VI)
 o Facial
(VII)
 o Vestibulocochlear
(VIII)
 o Glossopharyngeal
(IX)
 o Vagus
(X)
 o Spinal
Accessory
(XI)
 o Hypoglossal
(XII)
 • They have all functional components plus SPECIAL functions  

Figure 5.1 Different stages in the development of the spinal cord showing the neural crest cells, which will form the first afferent neurons in the sensory pathway

  Table 5.1. Functional Components of Cranial Nerves 

Table 5.2 Cranial Nerves according to function 

 

SENSORY
 (Afferents)


MOTOR
 (Efferents)


SOMATIC  SOMATIC
SENSORY
 General
Somatic
 Afferent
(GSA)
 VISION
&
HEARING
 Special
Somatic
 Afferent
(SSA)
 SOMATIC
MOTOR
 General
Somatic
 Efferent
(GSE)
 No
Special
Somatic
 Efferent
(SSE)


VISCERAL  VISCERAL
SENSORY
 General
Visceral
 Afferent
(GVA)
 SMELL
&
TASTE
 Special
Visceral
 Afferent
(SVA)
 VISCERAL
MOTOR
 General
Visceral
 Efferent
(GVE)
 BRANCHIOMERIC
 Special
Visceral
 Efferent
(SVE)



 • Positions
of
Functional
Components
in
Developing
Neural
Tube
 o Embryologically, the cut of neural tube is at the area of the  basal and alar plate, divided by the sulcus limitans   Basal plate – anterior thickening   Alar plate – posterior thickening  o Development of spinal cord has no movement, alar plate basal  of our dorsal horn; basal plate base of the ventral horn   o However there is a lateral rotation of the alar plate in the  brainstem, therefore it is more lateral here and the area of the  basal plate is ventral   o Efferent nuclei – basal; afferent – alar plate – becomes lateral  o GSE nuclei – most medial  o GSA nuclei – most lateral with an exception in the SSA due to  hearing.   • All
spinal
nerves
and
some
cranial
nerves
 o GSA
–
conscious
sensation
 o GVA
–
visceral
sensation
 o GVE
–
autonomic
nerve
fibers
 o GSE
–
voluntary
motor
to
skeletal
muscles
derived
from
 myotomes
or
somites
 • Some
Cranial
nerves
 o SVE
–
voluntary
motor
skeletal
muscles
derived
from
 branchiomeres


Sensory (CN I, II, VIII)
 
 Olfactory
 Optic
 Vestibulocochlear


Motor (CN III, IV,  VI, XI, XII)
 Oculomotor
 Trochlear
 Abducens
 Spinal
Accessory
 Hypoglossal


Mixed (CN V, VII,  IX, X)
 Trigeminal
 Facial
 Glossopharyngeal
 Vagus


  I. OLFACTORY NERVE (CN I)  • Functional
Components:
SVA
 • Run
from
the
nasal
mucosa
to
the
olfactory
bulb
–
there are many  olfactory nerves
 • Extend
thru
the
cribriform
plate
–
opening in the cranium where  the nerve passes
 • Lesion
to
these
nerves
or
cribriform
plate
fracture
may
yield
 anosmia (loss
of
smell)
 • CN
I
Schema
–
nuclei are called mitral and tufted cells located in  the olfactory bulb to reach the rhinencephalon (entorhinal area)
 o Note: Tufted cells and granular cells are smaller nerve cells  which synapse with the mitral cells
 
 II. OPTIC NERVE (CN II)  • Functional
Components:
SSA
 • Begin
at
the
retina
(axons of the ganglion),
run
through
the
optic  canal
to
the
optic chiasm
cross
over
and
continue
as
the
optic  tract
and
synapse
in
the lateral geniculate body
(thalamus)
 o Nucleus
of
optic
n.
=
lateral
geniculate
body
 • Optic
nerve
damage
yields
blindness
in
the
eye
served
by
the
 nerve
 • Optic
tract
damage
yields
partial
visual
loss
of both eyes because  of the shared fiber coming from both sides
 • Visual
defects:
Anopsias
/hemi‐anopsia
 Note: CN I and CN II are those nerves wherein their nuclei is not located at the brainstem. 


Group
21
|Grant,
Guadalupe,
Guevara
N,
Guevarra
M,
Guillermo
L,
Guillermo
M,
Gutierrez,
Hernandez,
Herradura

 

Page
3
of
6
 


III. OCULOMOTOR (CN III)  • “Eye
Mover”
 • Functional
Components:
GSE,
GVE
(due to innervations of the PNS)  (+GSA)

 o No cranial nerve is purely motor  • Originate
at
the
ventral
midbrain
 • Exit
skull
through
superior
orbital
fissure
 • Synapse
on:
 o Extraocular
muscles
  Superior
oblique,
inferior,
medial
and
superior
recti
(GSE)
 o Parasympatheic
innervation
to
iris
constrictor
muscle
and
ciliary
 muscle
(GVE)
  Any cranial nerve with a PNS or ANS has GVE function    Sympathetic is all In the thoracicolumbar part even if it is in  the head
 • Disorders
can
result
in
eye
paralysis:
Diplopia(double vision)
or
 Ptosis
(innervates the levator palpebrae ms)

 • CN
III
Nucleus
–
located
at
rostral
midbrain
 o Edinger‐Westphal
Nucleus
(GVE)
– for iris constrictor and ciliary ms  Consists of preganglionic parasympathetic fibers and terminate in the ciliary ganglion  Found posterior of oculomotor nucleus o Oculomotor
Nucleus
(GSE)
–
movement of EOM except for  superior oblique and lateral rectus    Its very much medial in the position of the brain stem; close  to your ventricular system 
  Found in anterior part of gray matter surrounding the cerebral aqueduct of the midbrain  Lies at the level of superior colliculus 
 IV.
TROCHLEAR
NERVE
(CN
IV)
 • Controls
the
superior
oblique
muscle
which
depresses
the
eye
via
 pulling
on
the
superior
oblique
tendon
which
loops
over
a
 ligamentous
pulley
known
as
the
Trochlea
 • Originates
on
the
dorsal
midbrain
exit
skull
through
the
superior
 orbital
fissure
and
synapses
on
the
superior
oblique
 • Functional
Components:
GSE
(+GSA
for
proprioception)
 • CN
IV
Nucleus
 o Trochlear
Nucleus
(GSE)
 o Found inferior to the oculomotor nucleus at the level of inferior colliculus 
 V.
TRIGEMINAL
NERVE
(CN
V)
 • Functional
Components:
GSA,
SVE
 • Biggest
cranial
nerve
 • Arises
from
ventrolateral
pons
with
Trigeminal
(Gasserian)
 ganglion
and
eventually
splits
into
3
divisions
 o Ophthalmic
(V1)
–
Superior
orbital
fissure;
goes
to
forehead;
 purely
sensory
 o Maxillary
(V2)
–
Foramen
rotundum;
goes
to
cheek;
purely
 sensory
 o Mandibular
(V3)
–
Foramen
ovale;
mixed
sensory
and
motor
 • Sensory
info
(touch,
temperature,
pain
and
position
sense)
from
 face
 • Motor
to
muscles
of
mastication
(branchiomeric)
 • CN
V
Nuclei
 o Mesencephalic
(midbrain)
nucleus
(GSA)
  For
proprioception

  Lateral
part
of
gray
matter
around
cerebral
aqueduct
at
 caudal
pons

 o Motor
nucleus
(SVE)
  Medial
to
sensory
nucleus



 At
rostral
pons

  Innervate
the
muscle
of
mastication,
tensor
veli

palatini
and
 other
muscles.

 o Main
sensory
nucleus
(GSA)
  For
touch
and
temperature

  Lateral
to
motor
nucleus
at
rostral
pons

  Continuous
below
with
the
spinal
nucleus

 o Spinal
nucleus
(GSA)
  Extends
inferiorly
through
whole
length
of
medulla
and
into
 part
of
the
spinal
cord
as
far
as
C2
segment
 
 VI.
ABDUCENS
NERVE
(CN
VI)
 • Functional
Components:
GSE
(+GSA)
 • Innervates
the
lateral
rectus
(extraocular)
muscle
 • Arises
from
lower
ventral
pons
passes
through
the
superior
orbital
 fissure
to
innervate
lateral
rectus
 • CN
VI
nucleus
 o Abducens
nucleus
(GSE)
  Notes:
 ‐ All
nerves
that
innervate
the
extraocular
muscles
exit
through
 the
superior
orbital
fissure.
 ‐ No
CN
is
purely
motor
since
there
will
always
be
a

sensory
 component
that
will
act
for
proprioception.




 VII.
FACIAL
NERVE
(CN
VII)
 • Functional
Components:
SVE,
GVE,
SVA,
GVA,
GSA

 • Originates
at
the
lower
pons
(Cerebellopontine
angle)
with
two
 nerve
roots
(Nervus
intermedius
and
facial
motor)
 • Exit
to
internal
acoustic
meatus
 • Motor
to
muscles
of
facial
expression
(branchiomeric):
(SVE)
 • Parasympathetic
motor
impulses
to
Lacrimal
Gland
and
 Submandibular,
Sublingual
&
Salivary
Glands
(GVE)
 • Sensory
information
from
taste
buds
on
anterior
2/3
of
the
 tongue
(SVA)
 • Sensation
over
skin
within
ear
canal
(GSA)
 • Deep
nasal
and
oral
cavities
via
geniculate
ganglion
(GVA)
 • Pterygopalatine
and
submandibular
ganglion
 • CN
VII
Nuclei
 o Facial
Motor
Nucleus
(SVE)
  Deep
in
the
reticular
formation
at
caudal
pons
 o Superior
Salivatory
Nucleus
(GVE)
  Found
posterolateral
of
the
motor
nucleus
of
CN
VII
  For
sublingual
and
submaxillary
gland
respectively
 o Lacrimatory
nucleus
(GVE)
  Parasympathetic
secretomotor
nerve
supply
to
the
lacrimal
 gland
 o Solitary
Nucleus
(SVA,
GVA)
  Rostral
part:
Taste
  Caudal
part:
Visceral
afferent
 o Spinal
Nucleus
of
CN
V
(GSA)
  For
sensation
of
ear
canal
  Note:  ‐ Superior salivatory, solitary, and spinal nucleus of
 cranial V are the components for nervus intermedius.
 
 VIII.
VESTIBULOCOCHLEAR
NERVE
(CN
VIII)
 • Functional
Components:
SSA
(For
hearing
and
balance)
 • Originates
at
the
pons
(Cerebellopontine
angle)
closely
associated
 with
CN
VII
 • Exit
through
Internal
Acoustic
meatus
to
innervate
the
inner
ear
 • 2
Divisions
 o Vestibular


Group
21
|Grant,
Guadalupe,
Guevara
N,
Guevarra
M,
Guillermo
L,
Guillermo
M,
Gutierrez,
Hernandez,
Herradura

 

Page
4
of
6
 


 Afferent
fibers
from
equilibrium
receptors
in
inner
ear
  Balance
 o Cochlear
  Afferent
fibers
from
cochlea
in
the
inner
ear
  Hearing
 • CN
VIII
Nuclei
 o Vestibular
Nuclei
(SSA)
  Superior,
Lateral,
Medial,
Descending
(Spinal
or
Inferior)
 o Cochlear
Nuclei
(SSA)
  At
pontomedullary
junction
in
caudal
pons
  Dorsal
(Posterior),
Ventral
(Anterior)
 
 IX.
GLOSSOPHARYNGEAL
NERVE
(CN
IX)
 • Functional
Components:
SVA,
GVE,
SVE,
GVA,
GSA
 • Fibers
emerge
from
lateral
medulla
at the post. olivary sulcus
 closely
associated
with
CN
X
 • Exists
skull
through
jugular
foramen
 • With
two
sensory
ganglia
(Superior
and
Inferior)
and
one
 parasympathetic
ganglion
(Otic)
–
for the parotid gland
 • Motor
Functions:
 o Motor
fibers
to
stylopharyngeus
muscle
(branchiomeric):
(SVE)
 o Parasympathetic
fibers
to
parotid
salivary
glands
(GVE
)
 • Sensory
Functions:

 o Taste
and
general
sensation
from
Pharynx
and
posterior
1/3
of
 tongue
(SVA)
 o General
Visceral
Afferent
(GVA)
information
from
 chemoreceptors
on
the
level
of
O2,
CO2
and
N
in
the
blood
(ex.
 carotid
body),
information
from
baroreceptors
on
BP
(ex.
 carotid
sinus)
 o Sensation
of
posterior
1/3
of
tongue
(GVA)
 o Sensation
on
skin
of
external
auditory
canal
(GSA)
 
 X.
VAGUS
NERVE
(CN
X)
 • Functional
Components:
GVE,
SVE,
GVA,
SVA,
GSA
 • Only
cranial
nerve
to
extend
beyond
head
and
neck
 • Fibers
emerge
from
lateral
medulla
inferior
to
CN
IX
and
leave
the
 skull
through
jugular
foramen
and
course
downwards
into
the
 thorax
and
abdomen
 • Has
two
sensory
ganglia
(Superior
and
Inferior)
 • Motor
Functions:
 o Parasympathetic
efferents
to
the
heart,
lungs
and
abdominal
 organs
up to the level of the distal one‐third of the transverse  colon (GVE)
 o Motor
fibers
to
palatal
pharyngeal
and
laryngeal
muscles
 (branchiomeric)
SVE
 • Sensory
Functions:
 o General
visceral
input
from
thoracic
and
abdominal
organs
 from
chemoreceptors
in
major
blood
vessels
(GVA)
 o From
taste
buds
in
posterior
pharynx
(SVA)
 o General
sensation
from
skin
in
ear
canal
(GSA)

 Ex. Ear and cotton buds ‘gag reflex’  • CN
IX
&
X
Nuclei
 o Nucleus
ambiguus
(SVE)
–
ms of branchiomeric origin (pharynx,  larynx, etc.; motor nucleus
 o Dorsal
motor
nucleus
(GVE)
–
for vagus; parasympathetic to GI  tract
 o Inferior
salivatory
nucleus
(GVE)
–
for parotid gland of  glossopharyngeal (parasympathetic nuclei)
 o Solitary
nucleus
(SVA,
GVA)
–
taste, pharynx, and GIT
 o Spinal
nucleus
of
CN
V
(GSA)
–
skin and external canal of ear

 XI.
SPINAL
ACCESSORY
NERVE
(CN
XI)


• Formed
by
the
union
of
a
cranial
root
and
a
spinal
root
 o CR
arises
from
lateral
medulla
(post‐olivary
sulcus),
while
the
 spinal
root
arises
from
cervical
spinal
cord
 o SR
passes
thru
the
foramen
magnum
and
joins
with
CR
to
form
 the
accessory
nerve;
They
then
leave
the
skull
via
the
jugular
 foramen
and
then
separates into cranial and spinal division
 • Cranial
division
then
separates
and
joins
vagus
and
innervates
 muscles
of
the
larynx,
pharynx
and
soft
palate
 • Spinal
division
innervates
the
sternocleidomastoid
and
trapezius
 muscles
 • CN
XI
Nuclei
 o Nucleus
Ambiguus
(SVE);
Motor
(Cranial
Root)
 o Accessory
Nucleus
(GSE);
Spinal
Root
 
 XII.
HYPOGLOSSAL
NERVE
(CN
XII)
 • Functional
Components:
GSE
(because the tongue is considered  skeletal)
(+GSA)
 • Arise
from
the
ventral
medulla
(Pre‐olivary
sulcus)
and
exit
the
 skull
via
the
hypoglossal
canal
and
innervate
the
tongue
 • Innervate
the
intrinsic
and
extrinsic
muscles
of
the
tongue
 o Swallowing,
speech,
food
manipulation
 • CN
XII
Nucleus
 o Hypoglossal
Nucleus
(GSE)
–
expected in the midline
 o With
eminence
above

Hypoglossal
trigone

 o Exit
via
pre‐olivary
sulcus
  Note:
 ‐ Sensory afferent are lateral and efferent once are the the medial  one seperated by the sulcus limitans   ‐ All nuclei are in the brainstem except CN 1 (olfactory bulb) and CN  2 (lateral geniculate body)    **Please refer to appendix A for table on Cranial Nerve Sensory  Nuclei  


VI. BRAINSTEM RULE OF “4”  • 4
medial
structures
starting
with
“M”
(medially located)
 o Motor
(Corticospinal)
pathway
 o Medial
Leminiscus
 o Medial
Longitudinal
Fasciculus
 o Motor
Nuclei
&
Nerves
 • 4
side
(lateral)
structures
starting
with
“S”
 o Spinocerebellar
pathway
 o Spinothalamic
pathway
 o Sensory
CN
V
nuclei
 o Sympathetic
pathway
 • 4
CN
in
Medulla
(CN 9‐12),
4
CN
in
Pons
(CN 5‐8),
4
CN
above
Pons
 (CN 1‐4)
 • 4
Motor
nuclei
in
medial
brainstem
divide
equally
into
12
(except
 1
&
2):
3,
4,
6,
12
 
 
 
 
 
 
 
 
 
 


• Functional
Components:
SVE,
GSE
(+GSA)
depends on the part
 Group
21
|Grant,
Guadalupe,
Guevara
N,
Guevarra
M,
Guillermo
L,
Guillermo
M,
Gutierrez,
Hernandez,
Herradura

 

Page
5
of
6
 


CRANIAL
NERVES
APPENDIX
 
 CN
 CN
ROOT


FUNCTIONAL
 COMPONENT
 (Major)


NUCLEUS


LOCATION


I 

Olfactory 

SVA 

Mitral and tufted cells 

Olfactory bulb 

II  V 

Optic  Trigeminal 

SSA  GSA 

Lateral Geniculate Body  Mesencephalic of V 

Thalamus  Midbrain  Pons  Cervical  Spinal Cord  Pons  Medulla 

VII 

Nervus Intermedus 

SVA 

Main Sensory and  Spinal of V  Solitary 

VIII 

Vestibular  Cochlear  Glossopharyngeal 

GSA  SSA  SSA  GSA  GVA 

Spinal of V  Vestibular  Cochlear  Spinal of V  Solitary (caudal) 

Pons  Medulla  Pons  Medulla  Medulla  Pons  medulla  Medulla 

SVA 

Solitary (rostral) 

Pons 

GSA 

Spinal of V 

Pons  Medulla 

GVA 

Solitary (caudal) 

Medulla 

IX 

X 

Vagus 

III 

Oculomotor 

SVA  GSE 

Solitary (rostral)  Oculomotor 

Pons  Midbrain 

IV  V 

Trochlear  Trigeminal  

GVE  GSE  SVE 

Edinger‐Westphal  Trochlear  Motor of V 

Midbrain  Midbrain  Pons 

VI 

Abducens 

GSE 

Abducens 

Pons 

DISTRIBUTION


Smell – Olfactory  Epithelium  Vision ‐ Retina  Joint and muscle  receptors of face  Skin and mucous  membranes of head  Taste – Anterior 2/3 of  tongue   Skin – external ear  Balance – Labyrinth  Hearing – Organ of Corti  Skin – external ear  Mucous membrane of  Pharynx, Carotid  Body/Sands, Middle ear  Taste – Posterior 1/3 of  tongue  Skin – external ear  meninges  Mucous membrane of  larynx, trachea, and GIT;  Aortic receptors   Taste ‐ oropharynx  Most extraocular ms.  Levator Palpebrae ms.  Iris constrictor; Ciliary ms  Superior Oblique ms  Jaw ms Tensor, Tympani  Tensor, Veli Palatin,  Anterior Belly of Digastric  Lateral Rectus ms. 




Group
21
|Grant,
Guadalupe,
Guevara
N,
Guevarra
M,
Guillermo
L,
Guillermo
M,
Gutierrez,
Hernandez,
Herradura

 

Page
6
of
6