Download neurology part1_lab10_10_5_2011

Cranial Nerves
Neuro lab: 10 part1 (the first hour of the lab)
Wednesday 11-5-2011
Last lecture we talked about the some of cranial nerves: oculomotor nerve,
optic nerve & abducent nerve & today we r going to continue talking about
Trigeminal nerve, facial & vestibulocochlear nerve
We previously mentioned the oculomotor nerve supplies all muscles of the
eye except (lateral rectus by abducent) & (superior oblique by troclear
nerve)
Each nerve has its own nucleus it might be motor or sensory & the largest
cranial nerve is the Trigeminal nerve
First: Trigeminal nerve
Which is mixed nerve sensory & motor both of them originate from its
own nucleus (sensory part-medial-from sensory nucleus) & (motor partlateral-from motor nucleus) both of them can be seen at the level of
medulla oblongata.
Sensory part of the trigeminal nerve enter inside the sensory ganglia
(trigeminal ganglia) contains pseudounipolar cells the fibers that exit from
it will divide into ascending & descending fibers.
 Ascending (sensory) fibers: they are fibers comes from the
periphery, most of its fibers will go to the main sensory nucleus
carry information of touch & pressure.
 Descending (sensory) fibers : most of its fibers go to the spinal
nucleus & carry information of pain & temperature
 Some of the fibers go to the (Mesencephlon) which receive
proprioception information
** All these fibers ((ascending, descending & proprioception)) will group
together & go to specific nucleus in the thalamus ** I think it’ll go to the
tectal station but I m not sure about it ** then to the cortex ((S1: postcentral
gyrus)) so the sensory fibers have different modalities
** All sensations will go to the thalamus except olfaction.
The motor part of the trigeminal nerve (which is located at the level of
pons) will descend to motor nucleus that supplies muscles of mastication
also o we have to know that it doesn’t make any synapse in the trigeminal
ganglia
The neurons of proprioception only pass beside the ganglia & make no
synapse.
All theses fibers will pass to the contra lateral side then through medial
leminscus to the thalamus then to the cortex
 Motor part of trigeminal:
The fibers will descend to the motor nucleus-at the level of pons medial to
the sensory nucleus- through trigeminal nerve then go to the muscles of
mastication
We have previously mentioned that the trigeminal ganglia is a
sensory ganglia & it will be divided into 3 parts
1-ophthalmic V1: from the superior orbital fissure
2-Maxillary V2: Foramen Rotundum
3-Mandibular V3: foramen ovale
 So the trigeminal nerve is sensory for the face
 SVE special visceral efferent for muscles like tensor palatini ,tensor
tympani & ant belly of digastric …etc
 GSA general somatic afferent from the skin of the face to trigeminal
ganglia to spinal or sensory ganglia
Sensory branches of the trigeminal nerve
1. The ophthalmic nerve (V1) carries sensory information from the scalp and
forehead, the upper eyelid, the conjunctiva and cornea of the eye, the nose
(including the tip of the nose, except alae nasi), the nasal mucosa, the
frontal sinuses, and parts of the meninges
2. The maxillary nerve (V2) carries sensory information from the lower
eyelid and cheek, the nares and upper lip, the upper teeth and gums, the
nasal mucosa, the palate and roof of the pharynx, the maxillary, ethmoid
and sphenoid sinuses, and parts of the meninges.
3. The mandibular nerve (V3) carries sensory information from the lower
lip, the lower teeth and gums, the chin and jaw (except the angle of the
jaw, which is supplied by C2-C3), parts of the external ear, and parts of
the meninges. The mandibular nerve carries touch/position and
pain/temperature sensation from the mouth. It does not carry taste
sensation (chorda tympani is responsible for taste), but one of its
branches, the lingual nerve carries multiple types of nerve fibers that do
not originate in the mandibular nerve.
So to sum up the trigeminal nerve has 4 nuclei
1- Spinal nucleus
2- Sensory nucleus
3- Motor nucleus
4- Mesencphalic nucleus
Also we knew that trigeminal ganglia is sensory ganglia group the
sensation to the nucleus in the brain stem whatever it was sensory motor
spinal then to the contralateral thalamus then to the primary sensory cortex
&it may so to the secondary sensory gyrus for the memory also we
mentioned that it is divided into 3 parts ophthalmic, maxillary &
mandibular, we also notices that there is minimal overlapping opposite to
the dermatomes where the overlapping is noticed.
Second: Facial Nerve (7th cranial nerve)
It’s mixed nerve has 3 main nuclei:
 Main motor nucleus
 Parasympathetic nucleus
 Sensory nucleus
The facial colliculus is an elevated area located on the dorsal pons. It is
formed by motor fibers of the facial nerve as they loop over the
abducens nucleus. Thus a lesion to the facial colliculus would result in
facial muscle paralysis.
  Motor Nucleus of facial nerve:
Responsible for the motor of the muscles of the face we can notice that
the motor fibers originate from it loop around the abducent nerve forming
(facial colliculus) to descend to facial muscles
* We have to know that the supplement of the face by the facial nerve is
divided into Upper part & Lower part
*The upper part receive corticonuclear fibers : which are fibers from the
cortex –previously mentioned the cranial nerves control the spinal nerves
by corticonuclear ((also called corticobulber)) which control the upper
part of the facial muscles & it is controlled by both hemispheres BUT
The lower part is controlled by the contralateral side of the cortex
  Sensory Nucleus of facial nerve:
It’s going to bring sensation from the face “ant 2/3 of the tongue” to
geniculate ganglia ((like the sensory trigeminal ganglia it contains
pseudounipolar cells to the sensory nucleus of facial nerve
So  From peripheral muscle like ant 2/3 of the tongue to geniculate
ganglia to the sensory ganglia of facial nerve ((we have to know that it’s
not separated it’s part of nucleus Solitaris—upper part of solitaris in
the medulla)) where it synapses to the thalamus then to the cortex
(postcentral gyrus) this is special sensation but general sensation of the
tongue by lingual nerve.
SoNucleus solitaris is a sensory nucleus that receive only sensory
information from sensory part of cranial nerves or sensory cranial nerves
& its upper part receive from facial nucleus
**Imp note: 1) There is no synapse in the geniculate ganglia of facial
nerves only there is cell bodies. 2) Ganglia: group of cell bodies outside
CNS 3) nucleus solitaris in the medulla oblongata
 Parasympathetic nucleus of facial nerve
It’s very near to the motor nucleus in the brain stem & it has 2 nuclei 1)
superior salivatory nucleus 2) lacrimal nucleus both of them send
preganglionic fibers to geniculate ganglia (No synapse) then go to the
parasympathetic to synapse then postsynaptic fibers to the glands &
smooth muscles
**If all the fibers (parasyp, sensory&motor)) gather they will form facial
nerve
**sensory for the ant 2/3 of the tongue by chorda tympani to geiculate
then contralateral thalamus
**Motor for muscles like mylohyoid & digastric... Etc
**parasymp originate of 2 nuclei which are called sup salivatory nucleus
& lacrimal nucleus their fibers are preganglionic parasymp to
pterygopalatine ganglion ((to the lacrimal gland)) &submandibular
ganglion ((to submandibular gland & sublingual gland))
The passage of facial nerve outside the cranial cavity through the
internal auditory meatus then outside the skull through stylomastoid
foramen through the parotid gland it’ll divide into 5 branches.
Types of its fibers:
a.
b.
c.
d.
SVE: special visceral efferent (for muscles of facial expression)
SVA: special visceral afferent
GSA: general somatic afferent
((I didn’t hear it well)) sorry please anyone know it write it on the
facebook group sorry again
According to dr alia she said that most of the questions in the exam are
about trigeminal & facial nerves also we have to know all the anatomical
info because they are included.
Third:Vestibulocochlear Nerve:
It’s the 8th cranial nerve, responsible for hearing & equilibrium , it’s
purely sensory
The information about hearing & equilibrium are carried through it which
enter to the internal auditory meatus with the facial nerve to the brain
stem at the junction between pons & medulla oblongata
It’s divided into 2 parts cochlear part responsible for hearing &
vestibular part for balance & equilibrium
(A) Vestibular ganglia is sensory ganglia contain cell bodies of
vestibular nerve & it’s in the periphery contain group of cell bodies but
vestibular nuclei it’s centrally located in the central nervous system
specifically in the brain stem.
Axons of the vestibular nerve synapse in the vestibular nucleus on the lateral
floor and wall of the fourth ventricle in the pons and medulla.
It arises from bipolar cells in the vestibular ganglion, ganglion of Scarpa,
which is situated in the upper part of the outer end of the internal auditory
meatus.
So vestibular nerve starts from periphery to the cell bodies in vestibular
ganglia ((which is in the internal auditory meatus)) to centrally toward brain
((brain stem)) then to the cortex but before it’ll pass through the thalamus.
**vestibular nerve make synapse in the vestibular complex send efferent
fibers for balance to cerebellum, spinal cord through vestibulospinal tract
then through MLF but the other fibers go to the vestibulospinal tract
(epsilateral).
We have to know that both cerebellum & vestibular nerve are responsible
for the balance
NOW the question the must come to our minds “why does it send its fibers
to cerebellum & spinal cord???!!!!
ANS: for controlling; this means cerebellum control it by the spinal cord
&part of it will be bound with the muscle of the eyes for movement during
running …etc
   Vestibular canal sends fibers to vestibular ganglia (sensory
ganglia) NO synapse to vestibular complex that sends some fibers to the
MLF, cerebellum & spinal cord to the thalamus finally to the cortex
(B) Cochlear Nerve:
Conduction from organ of corti inside cochlea to cochlear nucleus in the
brain stem then synapse ant & posterior ((ventral & dorsal)) to inferior
peduncle through hearing pathway synapse in the trapezoid body which has
nuclei of cochlear nerve –after synapse it must go to cortex but this doesn’t
occur- to the lateral leminscus to inf colliculus where it synapse then to the
tectum in the mid brain responsible for hearing.
NOTES:
 Superior colliculus for vision
 Inferior colliculus for hearing  to the medial genicualte body MGB
to the cortex ( temporal lobe 41 & 42 ) by radiation like what occurs
in the optic nerve
 Cochlear nerve pass at the junction between pons & medulla & enter
its nucleus (cochlear nucleus)…etc –previous pathway-
………to be continued
Done By: Dareen Matarweh :D
(Never give up on something if you think you can fight for it.
REMEMBER:
"It’s difficult to wait but it's more difficult when you regret.")