9/12 Brainstem3 - Rasin Flashcards
dorsal structures of pons
- facial colliculus (ventral aspect of 4th ventricle - choroid plexus-less; CP only found in part adj to medulla)
- hypoglossal trygone
- 3x cerebellar peduncles
relationship between pontine nuclei and cerebellar peduncles
transverse section : see large middle cerebellar peduncles made of axons and pontine nuclei
- axons of cells in pontine nuclei make up contralateral middle cerebellar peduncle!
conduit function of pons
descending pathways
- corticospinal/corticobulbar pathways
- anterior corticospinal pathway
ascending pathways
- DCMLS
- spinothalamic tract
CN V
sensory/motor components
trigeminal nerve
both motor (tiny efferent)/sensory (huge afferent) components
sensory components of CN V
1. GSA (general somatic afferent) from face for
- face x 3!!!
- pain and temp
- touch/pressure/conscious propriop.
- subconscious propriop.
- touch and pain for nasal sinuses, inside nose, inside mouth (oronasal mucous membranes/teeth), ant. 2/3 tongue
- pain for supratentoria dura mater (ant. part)
motor components of CN V
1. SVE (special visceral efferent) : muscles from branchial arches
- muscles of mastication
- tensor tympani m.
peripheral branches of CN V
CN V has 3 peripheral branches
- V1 opthalmic division
- V2 maxillary division (incl upper teeth)
- V3 mandibular division (incl lower teeth)
nuclei of CN V
CN V has 4 nuclei (3 sensory, 1 motor)
1. spinal trigeminal nucleus : pain/temp
- extends from pons through medulla to cervical levels (3 levels!)
2. chief/principal sensory nucleus : touch/pressure
- pons only
3. mesencephalic nucleus : subconscious proprioception
- extends from pons into mesencephalon
4. motor nucleus of V : muscles of mastication
trigemino-thalamic pathway
pain, temp, some touch
1st order neuron : trigeminal ganglion
- descends and synapses on spinal nucleus
2nd order neuron : spinal nucleus of V (medulla)
- decussation occurs at levels of pons and medulla (due to extended nature of nucleus) → cross to form trigeminothalamic fibers
3rd order neuron : VPM nucleus of thalamus
spinal trigeminal tract and nucleus
ipsi or contra?
where does decussation occur?
location/length
spinal nucleus carries GSA which conduct ipsilateral impulses of pain, temp, and some touch from head face and neck
- ipsilat because decussation occurs when second order neurons cross over to contralat side on way to VPM of thalamus (AFTER they synapse at spinal nuc)
location: lateral to cuneate tract/nucleus
- spinal tract superficial, spinal nucleus deep
extends form lower pons to upper cervical segments (C2-C3)
which artery affects pain and temp for face?
PICA!!!!
lateral medullary syndrome
- would lose pain/temp sensation on ipsilateral face
spatiotemporal maps of spinal trigeminal nucleus
imagine taking widening ice cream scoops out of the face
- scoop1 = nose/lips
- scoop2 = eye/chin
- scoop3 = top 2/3 of head/top of ear/chin
- scoop4 = middle of ext surface
within the spinal trigeminal nucleus, there is a column of cells each for V1, V2, V3, VII/IX/X (ventral → dorsal arrangement)
- the scoops are arranged 1-4 in a ventral→dorsal arrangement in each column!
what nerves (aside from V) contribute to the spinal trigeminal nucleus???
IX : sensation for back of ear, posterior 1/3 of tongue, upper pharynx (along with X/gagreflex)
- this is how pain/temp for both ant 2/3 (V) and post 1/3 (IX) end up in the same place!
X : sensation for pharynx, larynx, ext ear and dura of post fossa
VII : GSA from back of outer ear
trigemino-lemniscal pathway
touch, pressure (vibration/proprioception)
1st order neuron : trigeminal ganglion
- stays level and synapses on chief/principal trigeminal/sensory nucleus
2nd order neuron : principal sensory nucleus of V (pons)
- decussation occurs at levels of pons → cross to form trigeminal lemniscus
3rd order neuron : VPM nucleus of thalamus
location of principal sensory nucleus
posterior to CST and pontine nuclei, slightly more lateral on dorsal side
mesencephalic nucleus of V
what is received?
what is the function?
where is it located?
unconscious proprioception & “jaw jerk reflex”
**ONLY NUCLEUS THAT CONTAINS PRIMARY SENSORY AFFERENTS**
- jaw jerk reflex allowed for by connection of primary sensory afferents → motor nucleus of V
fx : controls the force of bite, conveys proprioceptive and pressure impulses from face
- teeth, peridontium, hard palate, muscles of mastication, joint capsule via muscle spindles and other mechanoreceptors
location: below superior cerebellar peduncles,
motor nucleus of V
innervates SVE : muscles of mastication and tensor tympani
- located slightly more medially (motor!)
summary for nuclei of V
everything ipsilateral!
- crossing occurs at neurons that project from the nuclei on up to thalamus/cortex
CN V lesions
- trigeminal neuralgia
- causes of sensory loss to face
- atrophy of affected side
- deviation of jaw to affected side on opening (due to pterygoid muscles that draw mandible forward/midline)
- loss of corneal/jaw jerk reflex
trigeminal neuralgia (Tic doloureux)
- recurrent episodes of brief severe pain lasting from seconds to mins (V2-V3)
- normal facial sensation
- mostly unknown cause
sensory loss of face
- trauma
- metastatic disease
- trigem/vestibular Schwannoma
- meninioma
- demyelination
- aneurysom of petrous portion of ICA
- infarcts
- herpes zoster
CN VII
components
facial nerve
carries both motor and sensory components
- involves multiple brainstem nuclei, but axons come together to form a single nerve at level of pontomedullary jx
2 efferent motor components
1. SVE (special visceral efferent) for muscles from branchial arches…
- muscles of facial expression, stapedius, part of digastric m.
2. GVE (general visceral efferent) to pregang PSNS to…
- saliv/lacrim-ation : lacrimal, sublingual, submandibular, all other salivary glands (EXCEPT parotid - IX)
3 afferent sensory components
1. GSA (general somatic afferent) : sensation from small region near outer ear
2. SVA (special visceral afferent) : taste from ant 2/3 tongue
3. GVA (general visceral afferent) : some nasopharynx mucous membrane
nuclei of VII
- motor nucleus of VII : SVE (muscles derived from branchial arches)
- superior salivatory nucleus : GVE (PSNS to salivary/lacrimation)
- rostral solitary nucleus : SVA (taste to ant 2/3 tongue)
honorable mention: spinal nucleus of V!
- GSA from back of outer ear (along with IX and X)
- crosses and ascends in trigeminothalamic tract to VPM_thalamus
nucleus involved with CN VII motor fx
facial motor nucleus
location/structures associated
what is innervated?
facial motor nucleus
- gives off axons that will loop around the abducens nucleus and form facial colliculus (bulging out of floor of 4th ventricle) in process
innervates. .. - muscles of facial expression
- stapedius
- digastric
need-to-know re: corticobulbar projection to motor nucleus of VII
UMNs from both ipsilat and contralat cortex synapse on LMN to upper face → bilat innervation
HOWEVER
ONLY UMN from contralat cortex synapse on LMN to lower face → contralat innervation only
implication: LESION THAT KNOCKS OUT UMN of one side will affect contralateral lower face!
- will be able to move eyebrows, but not able to smile on one side
reflexes involving motor nucleus of CN VII
- corneal → opthlamic nerve CN V (orbicularis oculi)
- sucking → mandibular nerve CN V (orbicularis oris)
- blinking_light → optic nerve CN II (orbicularis oculi)
- blinking_noise → cochlear nucleus CN VIII (orbicularis oculi)
- sound attenuation → cochlear nucleus (stapedius)
nucleus involved with CN VII motor function
superior salivatory nucleus
what’s innervated?
GVE : pregang PSNS to lacrimal, nasal mucosa, submandibular/sublingual salivary glands
nucleus involved with CN VII taste
rostral solitary nucleus
SVA (special visceral afferent) carrying taste from ant 2/3 of tongue
