Pons 3 (CN 5) Flashcards
what CN is found in the middle of the pons? how does it exit/enter?
CN5
laterally
does every brainstem level have a trigeminal nucleus?
yes, trigeminal nuclei at all levels of the brainstem
where is the medial lemniscus inside in the mid pons?
inside the tegmentum
what kind of sensory info does the ventral trigeminothalamic tract contain?
-where will it synapse?
2nd order crossed sensory info (from the opposite face)
-will synapse/terminate in the VPM thalamus
what kind of info does the dorsal trigeminothalamic tract contain? from what face?
- where will it synapse?
- what is it a constituent of
2nd order uncrossed sensroy info
- from the ipsi face
- will synapse/terminate in the VPM thalamus
- one constituent of the “trigeminal lemniscus”
where in the brainstem section can you see both the motor nucleus of V and the principal sensory nucleus of V
mid pons
level of CN 5
-motor nucleus is medial to the chief sensory nucleus of V
CN5 is threaded btwn the motor nucleus of V and the principal sensory nucleus of V
- where is the sensory info headed?
- where did the motor info orginiate and wehre is it headed?
- snsory headed towards principal nucleus
- motor info orginate from motor nucleus of V and is headed towards the muscles of mastication
CN 5 travels through the _____ and emerges wehre?
MCP
emerges out the lateral aspects of the midpons
a lesion in the midpons damaging the ML and STT (together now) would do what?
affect the general somatic sensations from the contralateral body
what do the fibers of CN 5 for the GSA mediate? what do the SVE innervate?
GSA: mediate general sensation from the face, eye, nasal, and oral cavities
SVE: innervates muscles of mastication (smaller motor component)
which division of the trigeminal nerve has motor fibers as well as general sensory fibers?
V3-mandibular division
where are V1, V2, and V3 located
V1 and V2 in the wall of the cavernous sinus
V3 is not in the cavernus sinus
where are motor commands coming from (at the mid pons level) and what will they head through
coming from the motor nucleus of V and will be heading through V3 to the muscles of mastication
how is sensory info coming in and into what?
sensory info is coming in via V1, V2, and V3 into the brainstem
-some info will be diving down to the medulla (spinal nucleus and tract of V) whereas other info will be heading to the principal sensory nucleus of V
will the motor nucleus of V receive corticobulbars (UMNs)?
yes
- it is motor to striated skeletal msucle, it is a LMN
- receives bilateral corticobulbars
where can the sensory afferents of CN5 synpase on
spinal trigeminal nuclues, chief snesory nucleus or the mesencephalic nucleus
what are the CNs that send sensory afferents to the spinal trigeminal nucleus
7, 9, 10-all convey sensory info from the skin around the ear to the spinal nucleus of V
5-conveys info from the face/head/orbit/dura from each of its 3 divisions (V1, V2, V3) to this same nucleus
where does the chief nucleus of V gets its sensory info from?
CN 5
what is the mesncephalic nucleus of V involed w/ ?
what things are invovled w/ this
proprioception
- TM joint
- muscles of mastication
where is the spinal trigeminal nucleus in mid pons?
gone, the kissing nuclei of V replace
what are the 4 trigeminal nuclei
spinal trigeminal nucleus
chief sensory nucleus of V
mesencephalic nucleus
motor nucleus of V
where do the peripheral processes bring in sensory info from?
what kind of snesory info do they contain
from the periphery via V1, V2, and V3
- info about pain, temp, and touch
- contains all 3 types of sensory fibers (pain, temp,touch)
the cells of the trigeminal ganglion send out “central prcoesses” to what
to the brainstem via CN5
- sensory afferents want to find a snesory trigeminal nucleus to synapse upon
- CN 5 enters the brainstem at the mid pons level
wehre do pain and temperature fibers synapse on in the 1st order trigeminalothalamic tract (periphery to CNS nucleus)
dive down to synapse on the caudal spinal trigeminal nucleus, located in the lateral medulla
what happens to light touch info on the 1st order trigeminalothalamic tract (peripher to CNS nucleus)
light touch bifucates, some goes to the rostral spinal trigeminal nucleus; some goes to the cheif sensory nucleus
what happens to 2 pt tactile in the 1st order trigeminothalamic tracts
goes exclusively to the cheif sensory nucleus
is there any 2 point tactile info in the medulla?
no
what do the 2nd order axons in the trigeminothalaitc tract synapse
thalamus
where does the ventral trigeminothalamic tract start
- where does it cross and what does it rise to synapse on
- what is it anatomically associated w/
- what kind of info does it convey
starts in the spinal trigeminal nucleus as well as in the principal sensory nucleus
- crosses the midline and rises to synapse on VPM thalamus
- anatomicall asso w/ the medial lemniscus
- conveys info about 3 types of general sneosry modalities NOT proprioception though
if you have a pt w/ unilateral loss of tactile facial sensation, the lesion is problaby…..
peripheral -1st order
where do 3rd order axons do?
where will they synapse
travel through the post limb of the internal capsule to finally synapse in the “face” area of the somatosensory cortex in the parietal lobe (post central gyrus)
- uncrossed
- PLIC to cortex basically…
where does medial lemniscus convey info from
where does trigeminal lemniscus convey info from
body
head/face
where does light touch info from the cornea head down to synapse in
the rostral spinal trigeminal nucleus
why does light touch info bifurcate?
sends corneal light touch down to the spinal trigeminal nucleus but allows other light touch info to go to the cheif sensory nucleus
-light touch info from the cornea can be close to the motor nuclei of VII…in the low PONS for corneal reflex
- why do corneal reflex afferents not ascned to VPM thalamus?
- where do they terminate
- what are their 2nd order neurons and wehre are they headed
- what are their 3rd order neurons and what do they innervate
bc it is a “reflex” and so doesn’t get the cortex involved
- terminate on the rostral spinal nucleus of V
- 2nd order neurons were internerons heading to the both motor nuclei of VII
- 3rd order neuron are the CN 7 LMNs that go out to innervate both orbicular oculi muscles to help you blink
in the corneal reflex, wehre are the interneurons sent out to synpase
both motor nuclei of VII
-polysnaptic …uses an interneuron
what happens after the motor fibers leave the motor nucleus of VII then loop around the nucleus of VI in the facial colliculus?
exit the low pons to eventually find the orbicularis oculi muscles to close both eyes
WE’RE AT THE PONS LEVEL
wehre do the corneal reflex fibers terminate in
the rostral spinal nucleus of V
if the left CN 7 is lesioned (a LMN or peripheral CN 7 palsy) and the right cornea is stimulated w/ a cotton wisp (light touch), what kind of response will you get
direct
if the right CN 7 is lesioned and the right cornea is stimulated, what type of response will you get
consensual
if the right CN 5 is lesioned and the right cornea is stimulated, what type of response will you get?
neither direct nor consensual
what can a lesion to V3 on one side lead to
deviation of the mandule to the side of the lesion, strong pushes the weak
-compare right and left masseter msucles during jaw clench
why do unilateral UMN lesions not produce jaw weakness?
bc the motor nuc of V gets bilateral UMN corticobulbars
what can UMN lesions cause? how can it be tested and what are you looking for
hyperreflexia
-clinically tested w/ the jaw jerk refelx, wehre you are looking for abnomrally, prominent, exaggerated jaw jerk
wehre do afferents of the jaw jerk refelx have its 1st cell body?
- wehre do 1st order peripheral processes of the mesencephalic nucleus come from?
- where is the central process sent out to synapse on?
NOT the trigeminal ganglion
- 1st cell body for the proprioceptive afferents from the jaw actually is the mesencephalic nucleus
- 1st order peripheral process of the mesencephalic nucleus comes from (innervates) the stretch receptors in the jaw for proprioception
- sent out to synapse on the motor nucleus of V in the mid pons
where does the efferent limb of the jaw jerk refelx send its motor axon to
jaw muscles to make them contract
there is no cell body in the trigeminal ganglion for jaw proprioception, so it is …..
monosynpatic
what is the weird exception to the CNS/PNS rule of gray matter and white matter
mesencephalic nucleus
