Cranial Nerves - Pons Flashcards by Emily Symon

What are the two parts of the pons?

(1) Tegmentum

(2) Basis Pontis

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What part of the pons is the dorsal portion containing cranial nerves and ascending and descending tracts?

Tegmentum

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What part of the pons lies just below the fourth ventricle?

Tegmentum

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What part of the pons is the ventral portion containing pontine nuclei and crossing pontine fibers running transversely which make up the middle cerebellar peduncle?

Basis Pontis

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What 3 large fascicles of fibers are contained within the ventral portion of the pons (basis pontis)?

corticospinal
corticobulbar
corticopontine

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The fibers of the ventral pons runs in which direction?

the caudal direction

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The cerebellar peduncles can be seen at what level?

the pontine level

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The cerebellar afferents enter the cerebellum through what parts of the cerebral peduncles?

inferior and middle

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The cerebellar afferents exit the cerebellum through what part of the cerebral peduncles?

superior

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What 4 cranial nerves are associated with the pons?

CN VIII (vestibulocochlear)
CN VII (facial)
CN VI (abducens)
CN V (trigeminal)

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What division of the CN VIII relays auditory information from the cochlea?

Cochlear division

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Auditory information is distributed bilaterally through what two areas?

the brainstem and cortical auditory areas

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Would a unilateral lesion of CNS auditory structures result in unilateral deafness?

NO (due to bilateral distribution)

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Damage to the CN VIII or both cochlear nuclei results in what? ipsilateral or contralateral?

ipsilateral deafness

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Is the cochlear system (auditory) topographically or tonotopically organized?

tonotopically organized

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What is the ultimate goal of auditory pathways? Be specific.

cerebral cortex (the superior surface of the superior temporal gyrus; Brodmann’s areas 41 and 42; primary auditory cortex; Transverse Temporal Gyri of Heschl

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When does cross-communication of auditory information occur? Before or after arriving at the cortex?

before arriving at cortex

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The bilateral representation of auditory information supports the ability to do what?

localize sound to one side

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The cochlear nerve consists of axons or central processes of neurons bringing afferent information from where?

the inner ear

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The cochlear nerve enters the brainstem where?

at the cerebellopontine angle

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After entering the brainstem, the cochlear nerve bifurcates to synapse in what?

bifurcates to synapse in BOTH dorsal and ventral cochlear nuclei

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Nuclei of the cochlear nerve are located where?

nuclei are superficial and located in rostral (open) medulla, adjacent to the base of the inferior cerebellar peduncle

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What are the 7 nuclei where the ascending pathways of the cochlear nerve synapse after the cochlear nuclei?

dorsal and ventral cochlear nuclei
superior olivary nucleus
lateral lemniscus
nucleus of inferior colliculus
brachium of inferior colliculus
medial geniculate nucleus
primary auditory cortex

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Pathway of protective auditory reflex?

inferior colliculus –> superior colliculus –> tectospinal tract ==> reflex turning of head to sound

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What does the superior olivary nucleus project to to dampen noise at the stapes?

Superior olivary nucleus projects to CN VII - stapedius muscle

What does the superior olivary nucleus project to to dampen noise at the malleus?

Superior olivary nucleus projects to CN V - tensor tympani

What is known as a tumor growing in the cerebellopontine angle?

acoustic neuroma

Where does the acoustic neuroma tumor (usually benign) begin?

on CN VIII

What is the result of an irritative lesion of the vestibular component of the cochlear nerve?

changes in perception of head position - spinning sensation, vertigo

Tinnitus refers to an irritative lesion that results in what?

ringing of the ears

In addition to CN VIII, acoustic neuroma can also involve what 3 other cranial nerves?

CN VII, V, IX

What 2 antibiotics are toxic to the CNS?

- penicillin | - streptomyocin

What CN has a "weak" spot in the change from the meninges to the connective tissue component of a peripheral nerve?

CN VIII

When toxic antibiotics are given for ear infections, they can effect what CN, specifically?

CN VIII

What cranial nerve is a mixed nerve for general sensation of the face and head area, as well as motor output tot he muscles of mastication?

CN V - trigeminal

The sensory part of the trigeminal nerve carry the same modalities as those carried in in what 2 systems/tracts?

the dorsal column system and the spinothalamic tract

The trigeminal nerve provides general somatosensation to what part of the face?

anterior 2/3 of the face

What are the 3 divisions of the trigeminal nerve?

V1 - opthalamic division; above the eye V2 - maxillary division; below the eye, above the mouth V3 - mandibular division; jaw

The LMNs of the trigeminal nerve innervate what?

muscles of mastication

The LMNs of the mandibular division of CN V are located where?

Motor nucleus of V (Trigeminal Motor Nucleus)

The LMNs of facial nerve are located where?

motor nucleus of VII (Facial Motor Nucleus)

The LMNs of facial nerve innervate what? contralateral or ipsilateral?

ipsilateral muscles of facial expression, platysma, and stapedius

Where do the axons of LMNs of the facial nerve exit the pons?

exits at anterolateral part of tegmentum of lower pons

UMNs innervation (corticobulbar) of facial nerve is bilateral to what part of the face?

bilateral to upper part of face representation

UMNs innervation (corticobulbar) of facial nerve is contralateral to what part of the face?

contralateral only to lower part of face representation

A lesion of the nucleus or the fibers of motor neurons of facial nerve result in what?

result in LMN signs in the innervated muscles - ipsilateral deficit

Where are the preganglionic parasympathetic neurons of the facial nerve located?

located in the reticular formation in the caudal pons

Where are the postganglionic cell bodies for tear production located?

pterygopalatine ganglion (lacrimal gland)

Where are the postganglionic cell bodies for salivation located?

submandibular ganglia (submandibular and sublingual glands)

The cell bodies for taste (from anterior 2/3 of tongue) are found where?

rostral part of the solitary nucleus (NTS)

The axons of taste (from anterior 2/3 of tongue) project where?

project from the NTS ipsilaterally to the VPM then to the gustatory area of the cortex - parietal lobe and insula

What is the pathology that results from a LMN deficit to muscles of facial expression?

Bell's Palsy

UMN lesions of the facial nerve result in what?

deficit on contralateral lower face only

What is the blink reflex?

touch the cornea and both eyes close

Direct response of the blink reflex?

closure of the touched eye

Indirect or consensual response of the blink reflex?

closure of the untouched eye

What is the receptor of the blink reflex?

free nerve ending in cornea (peripheral process of sensory neuron in the opthalamic division of CN V (elicit with cotton wisp)

The central process of the afferent limb of the blink reflex ends in what nucleus?

central process ends in main sensory nucleus of V

The interneurons of the blink reflex in the main sensory nucleus of V project where?

project directly to ipsilateral facial motor nucleus and to RF interneurons

The direct reflex efferent limb of the blink reflex projects from what nucleus to where?

ipsilateral facial motor nucleus to orbicularis oculi (BLINK)

The indirect reflex efferent limb of the blink reflex projects from what nucleus to where? to activate what?

RF interneurons project to contralateral facial motor nucleus to activate contralateral orbicularis oculi (BLINK)

Symptoms of lesions to the facial nerve?

- LMN deficit of ipsilateral face - dry cornea; ulcerated cornea - loss of taste over ipsilateral anterior 2/3 of tongue - inability to produce saliva - hyperacusis - stapedius can't dampen sound

Motor nuclei located in the pons (4)?

- Abducens Nucleus (CN VI) - Superior Salivary Nucleus (CN VII) - Facial Motor Nucleus (CN VII) - Trigeminal Motor Nucleus (CN V)

Sensory nuclei located in the pons (6)?

- Solitary Nucleus (taste part) - Superior Vestibular Nuclei - Lateral Vestibular Nuclei - Main Sensory Trigeminal Nucleus - Mesencephalic Trigeminal Nucleus - Spinal Trigeminal Nucleus

Sensory component of facial nerve?

taste of anterior 2/3 of tongue

Somatic motor component of facial nerve?

muscles of expression; reflexive control of auditory sounds - stapedius

Autonomic motor component of facial nerve?

lacrimal gland, submandibular and sublingual gland

Loss of somatic motor component (muscles of facial expression) results in what?

Bell's Palsy