Cranial Nerve - Pons Flashcards
What two parts is the pons divided into?
- Tegmentum
2. Basis Pontis
Select the proper portion of the Pons:
Dorsal Portion
a. Tegmentum
b. Basis Pontis
a. Tegmentum
Select the proper portion of the Pons:
Contains pontine nuclei and crossing pontine fibers running transversely.
a. Tegmentum
b. Basis Pontis
b. Basis Pontis
Select the proper portion of the Pons:
Ventral Portion
a. Tegmentum
b. Basis Pontis
b. Basis Pontis
Select the proper portion of the Pons:
Contains cranial nuclei and ascending and descending tracts.
a. Tegmentum
b. Basis Pontis
a. Tegmentum
Select the proper portion of the Pons:
This region lies just below the forth ventricle.
a. Tegmentum
b. Basis Pontis
a. Tegmentum
Select the proper portion of the Pons:
Marked by large fasicles of fibers containing corticospinal, corticobulbar, and corticopointine axons.
a. Tegmentum
b. Basis Pontis
b. Basis Pontis
The Basis Pontis contains pontine nuclei and corssing pontine fibers running transversely which make up
middle cerebellar peducle
In the Basis Pontis, large fasicles of fibers containing corticospinal, corticobulbar, and corticopointine axons are running in what direction?
caudal
What are the 3 cerebellar peduncles
inferior, middle, and superior
All 3 cerebral peducles can be seen at what level?
pontine level
As a general principle, the cerebellar peduncles allow for
cerebellar afferents to enter (inferior and middle) and exit (superior) the cerebellum.
Which Cranial Nerves are associated with the pons?
CNVIII - Vestibularcochlear
CNVII - Facial
CNVI - Abducens
CNV - Trigeminal
What is the function of the Cochlear Division of CNVIII Vestibulochochlear Nerve?
relay of auditory information from specialized receptor, the cochlea.
Auditory information is distributed (IPSILATERALLY, CONTRALTERALLY, BILATERALLY) through the brain stem and cortical auditory areas.
Auditory information is distributed BILATERALLY through the brain stem and cortical auditory areas.
T/F: Unilateral lesions of the CNS auditory structures do not result in unilateral deafness.
True
T/F: Damage to the CNVIII or both cochlear nuclei will result in ipsilateral deafness.
True
If sensory stems are topographically organized, how is the entire auditory system organized?
tonotopically
Specifically what is the ultimate end goal of auditory pathways?
cerebral cortex:
- the superior surface of the superior temporal gyrus (within the lateral sulcus)
- Broadmann’s areas 41 and 42
- Pirmary Auditory Cortex
- Transverse Temporal Gyri of Heschl
T/F: Much cross-communication takes place in the auditory pathway before arriving at cortex.
True
The bilateral representation is complex and actual relay steps are unclear. It does however support the ability to localize sound to one side.
The Cochlear Nerve consists of axons or central processes of neurons containing what information?
bringing afferent information from the inner ear.
Where does the Cochlear Nerve enter the brainstem?
cerebellopontine angle
Once the Cochlear Nerve enters the brainstem at the cerebellopontine angle, what does it do?
bifurcates to synapse
After the Cochlear Nerve enters the brainstem and bifurcates where does it synapse?
in both dorsal and ventral cochlear nuclei
Where are the dorsal and ventral cochlear nuclei located?
both are superficial and located in rostral (open) medullar, adjacent to the based of the inferior cerebellar peduncle.
What are the seven synapses that occur for the Cochlear Nerve?
- Dorsal and Ventral Cochlear Nuclei
- Superior Olivary Nucleus
- Lateral Lemniscus
- Nucleus of Inferior colliculus
- Brachium of inferior colliculus
- Medial geniculate nucleus
- Primary auditory cortex
What is the pathway for the protective auditory reflex of turning head TO sound?
Inferior Colliculus >
Superior Colliculus >
Tectospinal Tract
Which nucleus is important for protection against loud noise?
Superior olivary nucleus
What are the two areas which the superior olivary nucleus can dampen noise?
- Stapes
2. Malleus
What cranial nerve does the olivary nucleus use to dampen noise at the stapes?
CNVII Facial
What cranial nerve does the olivary nucleus use to dampen noise at the malleus?
CNV Trigeminal
What muscle does the superior olivary nucleus project to the CNVII Facial to dampen noise at the stapes?
Stapedius Muscle
What muscle does the superior olivary nucleus project to the CNV Trigeminal to dampen noise at the malleus?
Tensor Tymapni Muscle
What is Acoustic Neuroma?
Tumor growing in the cerebellopontine angle, usually benign and beginning on the VIII Vestibulocochlear Nerve
What affect does the Acoustic Neuroma have on the Vestibular Component of VIII Vestibulochchlear?
irritative lesion; changes in perception of head position - spinning sensation, vertigo
What affect does Acousitc Neroma have besides the vestibular component?
Tinnitus (rinning of the ears); irritative lesion.
What nerves can Acoustic Neuroma also involve?
CNVII Facial
CNV Trigeminal
CNIX Glossopharyngeal
How can antibiotics affect the auditory system?
Antibiotic Toxicity - some antibiotics are toxic to the CNS (penicillin, streptomyocin) When given for ear infections, they can effect CNVIII Vestibulochoclear specifically.
Why can antibiotics effect CNVIII vestibulochoclear specifically?
This CN has a “weak” spot in the change from meninges to the connective tissue component of a peripheral nerve.
What is the function of CNV Trigeminal?
Mixed nerve for general sensation of the face and head area, as well as motor output to the muscles of mastication.
The sensory parts of CNV Trigeminal carry the same modalities as those carried in
both the dorsal column medial lemniscal and spinothalamic tract.
CNV Trigeminal carries general somatosensation for
anterior 2/3 of face
CNV Trigeminal is broken up into what divisions?
V1 - Opthalmic Division
V2 - Maxillary Division
V3 - Mandibular Division
CNV Trigeminal V1 - Opthalmic Division is responsible for somatosensation
above the eye
CNV Trigeminal V2 - Maxillar Division is responsible for somatosensation
below the eye, above the mouth
CNV Trigeminal V1 - Mandibular Division is responsible for somatosensation
jaw
Lower motor neurons of CNV Trigeminal innervate
muscles of mastication and a couple of other muscles:
- Nerve to Mylohyoid (mylohyoid muscle and the anterior belly of the digastric muscle)
- Tensor Tympani
Muscles of mastication are restricted to which division(s) of CNV Trigeminal?
Mandibular Division of CNV
Where do the axons for CNV Trigeminal motor division synapse in the middle pons?
Motor Trigeminal Nucleus (CNV)
What are the components of the CNVII Facial?
Sensory
Somatic Motor
Autonomic Motor
What is the function of the Sensory component of CNVII Facial?
Taste anterior 2/3 of tongue
What is the function of the Somatic Motor component of CNVII Facial?
Muscle Expression
and
Reflexive control of auditory sounds - Stapedius
What is the function of the Autonomic Motor component of CNVII Facial?
Lacrimal Gland
Submandibular Gland
Sublingual Glands
LMN in motor nucleus of VII innervate (IPSILATERAL, CONTRALTERAL, BILATERAL) muscles of facial expression.
LMN in motor nucleus of VII innervate IPSILATERAL muscles of facial expression.
What muscles of facial expression do LMN in motor nucleus of VII innervate ipsilatteraly?
Platysma and Stapedius
Where do LMN in motor of nucleus VIII exit?
anterolateral part of tegmentum of lower pons
CNVII Facial motor neurons in motor nucleus are for muscle on
half of face
somatotopic organisation
CNVII Facial UMN innervation (corticobulbar) is (IPSILATERAL, CONTRALTERAL, BILATERAL) to upper part of face representation.
UMN innervation (corticobulbar) is BILATERAL) to upper part of face representation.
CNVII Facial UMN innervation (corticobulbar) is (IPSILATERAL, CONTRALTERAL, BILATERAL) to lower part of face representation.
UMN innervation (corticobulbar) is CONTRALTERAL to lower part of face representation.
A lesion of the nucleus or the fibers of CNVII Facial LMN results in
LMN signs in the innervated muscle as motor neurons are final common pathway.
What are the signs of LMN lesions and are the signs ipsilateral or contralateral?
- Flaccid paralysis (atonia or hypotonia)
- Areflexia or hyporeflexia
- Atrophy of muscle (muscle wasting)
- Fasciculations and fibrillations
Signs should be ipsilateral because LMN in motor nucleus of VII innervate ipsilateral muscles of facial expression
Where are CNVII Facial preganglionic parasympathetic neurons located?
reticular formation in the caudal pons
What are CNVII Facial preganglionic parasympathetic neurons responsible for?
- Tear Production
2. Salivation
Where are CNVII Facial postganglionic cell bodies located for tear production?
pterygopalatine ganglion (lacrimal gland)
Where are CNVII Facial postganglionic cell bodies located for salivation?
submandibular ganglia (submandibular and sublingual glands)
What branch of the CNVII facial nerve is responsible for taste from anterior 2/3 of tongue?
chorda tympani
Through what tract do CNVII Facial Nerve Chorda Tympani run through?
Rostral part of Solitary Nucleus (NTS)
What synapses in the caudal part of NTS?
cardio-respiratory and gastrointestinal processes
Where does CNVII Facial Nerve Chorda Tympani project to from NTS?
VPM
CNVII Facial Nerve Chorda Tympani projects from NTS (IPSILATERALLY, CONTRALATERALLY, BILATERALLY) to VMP.
CNVII Facial Nerve Chorda Tympani projects from NTS IPSILATERALLY to VMP.
CNVII Facial Nerve Chorda Tympani projects from NTS ipsilaterally to VMP to ___
gustatory area of cortex - parietal lobe and insula
What is Bell’s Palsy?
CNVII Facial Nerve LMN deficit to muscles of facial expression.
CNVII Facial Nerve UMN lesions - deficit on (IPSILATERAL, CONTRALATERAL, BILATERALLY) lower face.
contralateral lower face only
Why is CNVII Facial Nerve UMN lesions deficit on contralteral lower face only?
UMN innervation (corticobulbar) is contralateral only to lower part of face representation.
What are symptoms of lesions for LMN deficit for CNVII Facial Nerve?
ipsilateral face
- Dry cornea; ulcerated cornea.
- Loss of taste over ipsilateral ant. 2/3 of tongue.
- Inability to produce saliva.
- Hyperacusis - stapedius can’t dampen sound.
-Only lower motor deficit of muscles of facial expression (Bell’s Palsy.)
What cranial nerves is Corneal Blink Reflex carried by?
CNV Trigeminal
CNVII Facial Nerve
What is the Blink Reflex?
courch the cornea and both eyes close
What is the Direct Reflex of blink reflex?
closure of touched eye (ipsilateral)
What is the Indirect or consensual response of blink reflex?
closure of untouched eye (contralteral)
Circuits of Blink Reflex: what is the receptor and what is its peripheral process CN?
free nerve ending in cornea (peripheral process of sensory neuron in the opthalmic division of CNV Trigeminal - elicit with cotton wisp)
Circuits of Blink Reflex: where does the afferent limb, opthalmic division of CNV Trigeminal, central process end?
Main Sensory Nucleus of V Trigeminal
Circuits of Blink Reflex: interneurons in Main sensory Nucleus of V project directly to ____ and ___.
interneurons in main sensory nucleus of V project directly to IPSILATERAL facial motor nucleus and to RF interneurons.
Circuits of Blink Reflex: the Direct Reflex efferent limb runs from ___ to ___
ipsilateral facial motor nucleus to orbicularis oculi - BLINK
Circuits of Blink Reflex: the Indirect Reflex efferent limb runs from ____ to ____
RF internerons project to contralateral facial motor nucleus to activate contralateral orbicularis oculi - BLINK
If the ipsilateral afferent limb, Opthalmic Division of CNV Trigeminal, from the Sensory Receptor to Main Sensory Nucleus V Trigeminal is cut, what will the result be?
No blink either side.
If the efferent limb from ipsilateral Facial Motor Nucleus VII to Orbicularis Oculi is cut, what will the result be?
Loss of direct response, ipsilateral facial paralysis
If the efferent limb from Main Sensory Nucleus V Trigeminal to ipsilateral Facial Motor Nucleus VII is cut, what will the result be?
Loss of direct response, no evidence of facial paralysis
If the RF interneuron from Main Sensory Nucleus V Trigeminal to contralateral Facial Motor Nucleus VII, what will the result be?
Loss of indirect response, no evidence of facial paralysis.
If the efferent limb from contralateral Facial Motor Nucleus VII to orbicularis oculi is cut, what will the result be?
Loss of indirect response, contralateral facial paralysis