cranial nerves and special senses -...
TRANSCRIPT
Word roots • vagus (L.): wandering
• trochlea (G.): pulley
• glossus (G.): tongue
• cochlea (L.): snail
• chiasm (L.): cross
• rectus (L.): straight
• ocul, -i, -o (L.): eye
• opt- (L.): eye (optic, opthalmic etc.)
Special senses
• 5 „„traditional‟‟ senses: Touch, smell, sight,
hearing and taste.
• “touch” is what we have already talked about,
and is a colloquial term for general sensation.
This is covered by peripheral nerves and
cranial nerves.
• The cranial nerves cover the special senses,
and equilibrium (not traditionally covered).
Cranial nerves • Cranial nerves (CN) are part of the
PNS.
• Nerves attach to the brainstem
(except for CNI and CNII - direct
connection to brain).
• Synapse within distinct nuclei
(collections of cell bodies) in brainstem
(equivalent to grey matter of the spinal
cord).
Mnemonics 12 cranial nerves
Oh
Oh
Oh
To
Touch
And
Feel
Very
Gooey
Veal
And
Ham
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Accessory
Hypoglossal
Some
Say
Marry
Money
But
My
Brother
Says
Big
Boobs
Matter
More
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII S - sensory
M - motor
B - both
Moore and Dally (2009). Clinically Oriented Anatomy
Cranial nerve nuclei
Collections of grey
matter within distinct
locations throughout
the brainstem.
These are equivalent
to the grey matter
collections (ventral
and dorsal horns) in
the spinal cord.
CN I : Olfactory Sensory only
Special sense: Smell
Passes through cribriform
plate of ethmoid bone
and synapses
immediately onto
olfactory bulb (second
order neurons)
No connection to thalamus
Internal view of the skull
CN II : Optic
Sensory only
Sight (special sensory)
Passes through optic
canal in sphenoid
bone
Neurons from retina
(back of eyeball)
Half of neurons cross
over at optic chiasm
(peripheral visual
fields)
Visual Pathway
Visual fields
Retinal fields
Optic nerve
Optic chiasm
Optic tract
Lateral geniculate
body (thalamus)
Optic radiation
Visual cortex
(occipital lobe)
First order neuron in eyeball
Second order neuron from
eyeball to thalamus
Third order neuron from
thalamus to occipital lobe
Eye Three layers of the
eyeball:
* fibrous coat
- cornea (transparent)
- sclera (white part)
* vascular coat (uvea)
- iris
- lens
- choroid (vessels)
* neural coat
- retina --> synapse to
neurons that form CN II
Ellis (2010) Clinical Anatomy
Vision
Vision
CN III:
Oculomotor
Motor (Autonomic and
Somatic)
Passes through
superior orbital fissure
of sphenoid bone
controls extrinsic eye
muscles (movements
of the eyeball)
controls size of pupil
and shape of lens
CN IV:
Trochlear
Motor (somatic)
Passes through
superior orbital fissure
Controls the Superior
oblique muscle
moves the eye down
and out
Small ligament holds the superior oblique
muscle in place. This acts like a pulley,
which is where this nerve gets it‟s name
from.
Superior view of left orbit
CN V:
Trigeminal Sensory and motor
(depending on
branches)
Three branches:
- Opthalmic (V1)
- Maxillary (V2)
- Mandibular (V3)
Only mandibular has
motor fibres (controls
muscles of
mastication)
Supraorbital notch
(part of V1)
Infraorbital foramen
(part of V2)
Mental foramen
(part of V3)
Exit foramina for CNV
(sensory branches)
CN V:
Trigeminal All three branches provide
sensory innervation to the
face
Each branch passes
through a different hole in
the skull:
- Opthalmic - superior
orbital fissure
- Maxillary - foramen
rotundum
- Mandibular - foramen
ovale
Sensory distribution of trigeminal nerve
Tongue
Moore and Dally (2009). Clinically Oriented Anatomy (modified)
Ellis (2010). Clinical Anatomy (modified)
CN VI:
Abducens
Motor (somatic)
Nerve passes through
superior orbital fissure
in the skull
controls the Lateral
rectus muscle
abducts the eyeball
Eye - many cranial nerves
involved! 3 muscles to control extrinsic eye
muscles
* CN III oculomotor - medial rectus,
superior recuts, inferior rectus,
inferior oblique
* CN IV trochlear - superior oblique
* CN VI abducens - lateral rectus
CNIII, the oculomotor nerve, has
parasympathetic fibres. This controls
the size of the pupil (how much light
enters the eye) and the shape of the
lens.
CN II, optic nerve carries the visual information
back to the visual cortex, where it is interpreted
and integrated with other information.
CN VII, facial nerve carries PSNS fibres to
teh lacrimal gland. This produces
lubricating film (tears) that keeps the eye
moist.
Moore and Dally (2009). Clinically Oriented Anatomy
CN VII:
Facial
Motor (somatic and
autonomic) and
special sensory
Passes through the
internal acoustic
meatus, through
temporal bone, exits
stylomastoid foramen
Special sensory to
tongue (taste)
Motor to muscles of
facial expression
Facial nerve
Special sensory:
Taste
Anterior 2/3 tongue
Moore and Dally (2009). Clinically Oriented Anatomy (modified)
The facial nerve also
supplies PSNS
innervation to the
lacrimal glands (tears)
and salivary glands.
CN VIII:
Vestibulocochle
ar
Sensory (special)
Hearing (cochlear
part)
Equilibrium
(vestilbular part)
Passes through
internal acoustic
meatus
Cochlea (L.) = snail
Marieb (2009). Human Anatomy and Physiology (modified).
Martini (2009). Human Anatomy and Physiology (modified).
Martini (2009). Human Anatomy and Physiology (modified).
CN IX:
Glossopharynge
al
Motor (somatic) and
sensory (special and
somatic)
Passes through the
jugular foramen
sensory for the tongue
(general sensation and
taste)
sensory for the pharynx
(throat)
Glossopharynge
al
nerve
The glossopharyneal nerve
provides general sensation
(touch, pain, temperature etc)
AND
special sensation to the
posterior 2/3 of the tongue
CN X: Vagus
Motor (somatic and
autonomic)
Passes through jugular
foramen
Voluntary motor control
of laryngeal muscles
(controls voice)
Autonomic (PSNS)
motor control of gut,
salivary glands, heart
rate (slows).
CN X: Vagus
CN XI:
Accessory Motor (somatic)
Ascends through
foramen magnum,
then passes through
jugular foramen
Trapezius
Sternocleidomastoid
Pons
Thalamus
Medulla
oblongata
CN XII:
Hypoglossal
Motor (somatic)
Passes through
hypoglossal canal (near
foramen magnum)
Distinct location - roots
between olives and
pyramids on medulla
oblongata
Voluntary motor control of
tongue muscles Anterior view of dissected
brain stem and thalamus
Tongue
Trigeminal nerve (CNV)
GENERAL SENSORY Facial nerve (CNVII)
TASTE
Glossopharyngeal
nerve (CNIX)
TASTE and GENERAL
SENSORY
MOTOR = HYPOGLOSSAL only! XII
Skull foraminae
Peripheral nerves (test
yourself)
Posterior compartment of the thigh
Radial nerve
Sensory innervation to the face
Motor innervation of facial muscles
Intrinsic foot muscles plantar surface
Spinal segments of brachial plexus
Peripheral nerves (test
yourself)
Posterior compartment of the thigh
Radial nerve
Sensory innervation to the face
Motor innervation of facial muscles
Intrinsic foot muscles plantar surface
Spinal segments of brachial plexus
Tibial n.
Posterior arm and forearm
muscles
C5-T1
Lateral and medial plantar nerves
(Tibial n.)
Trigeminal nerve CNV
Facial nerve CNVII
Test yourself
Test yourself Corpus callosum
Frontal lobe
Anterior cerebral
artery
Pons 4th ventricle
cerebellum
parieto-occipital
sulcus
