brain stem iii basic neuroscience james h. baños, ph.d
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Brain Stem IIIBrain Stem III
Basic NeuroscienceBasic Neuroscience
James H. Baños, Ph.D.James H. Baños, Ph.D.QuickTime™ and a
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YesterdayYesterday CN ICN I CN IICN II CN IIICN III CN IVCN IV CN VICN VI
TodayToday CN VCN V CN VIICN VII CN VIIICN VIII CN IXCN IX CN XCN X CN XICN XI CN XIICN XII
CN V - TrigeminalCN V - Trigeminal
CN V - TrigeminalCN V - Trigeminal
CN V is the general sensory nerve CN V is the general sensory nerve for the headfor the head TouchTouch ProprioceptionProprioception Pain/temperaturePain/temperature
CN V and its connections are to the CN V and its connections are to the head what dorsal roots and the head what dorsal roots and the spinal cord are to the bodyspinal cord are to the body
Also has a motor componentAlso has a motor component
CN V - TrigeminalCN V - Trigeminal
Trigeminal = “tri” + “geminus”Trigeminal = “tri” + “geminus” Tri = 3Tri = 3 Geminus = at the same birthGeminus = at the same birth
“Three at the same birth”
CN V - TrigeminalCN V - Trigeminal
Peripheral afferent fibers distributed Peripheral afferent fibers distributed in three divisionsin three divisions VV11 - Ophthalmic - Sensory only - Ophthalmic - Sensory only
VV22 - Maxillary - Sensory only - Maxillary - Sensory only
VV33 - Mandibular - Sensory and motor - Mandibular - Sensory and motor
CN V - TrigeminalCN V - Trigeminal
Peripheral sensory afferents Peripheral sensory afferents converge at the trigeminal ganglionconverge at the trigeminal ganglion
This is a homologue of the dorsal This is a homologue of the dorsal root ganglion of spinal sensory root ganglion of spinal sensory nervesnerves
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CN V - TrigeminalCN V - Trigeminal
Discriminative touch and conscious Discriminative touch and conscious proprioceptionproprioception The The main sensory nucleusmain sensory nucleus of V is a of V is a
homologue of dorsal column nuclei homologue of dorsal column nuclei (gracilis and cuneatus)(gracilis and cuneatus)
CN V - TrigeminalCN V - Trigeminal
Spinal Cord:Spinal Cord:
Dorsal ColumnsNG
NC
ThalamusMedial Lemniscus
CN V - TrigeminalCN V - Trigeminal
Trigeminal System:Trigeminal System:
CN VV
Main sensory nucleus of V
Dorsal ColumnsNG
NC
ThalamusMedial Lemniscus
CN V - TrigeminalCN V - Trigeminal
VV
Main sensory nucleus of V
NG NG NCNC
CN V - TrigeminalCN V - Trigeminal
Mesencephalic nucleus of VMesencephalic nucleus of V Actually not a true nucleusActually not a true nucleus Cell bodies of what would otherwise be Cell bodies of what would otherwise be
the ganglionic portion of proprioceptive the ganglionic portion of proprioceptive fibers from the muscles of the jawfibers from the muscles of the jaw
CN V - TrigeminalCN V - Trigeminal
VV
Main sensory nucleus of V
Mesencephalic nucleus of V
CN V - TrigeminalCN V - Trigeminal
Pain and temperaturePain and temperature The The spinal nucleus of Vspinal nucleus of V is a long upward is a long upward
extension of the posterior horn of the extension of the posterior horn of the spinal cordspinal cord
It contains a set of neurons resembling It contains a set of neurons resembling the substantia gelatinosa in the spinal the substantia gelatinosa in the spinal cordcord
The tracts entering the spinal nucleus of The tracts entering the spinal nucleus of V are like an upward extension of the V are like an upward extension of the tract of Lissauertract of Lissauer
CN V - TrigeminalCN V - Trigeminal
Pain and temperaturePain and temperature Trigeminal pain and temperature fibers Trigeminal pain and temperature fibers
descend caudally to enter the spinal descend caudally to enter the spinal nucleus of Vnucleus of V
Fibers from the spinal nucleus of V Fibers from the spinal nucleus of V decussate and join the ascending decussate and join the ascending spinothalamic tractspinothalamic tract
CN V - TrigeminalCN V - Trigeminal
VV
Main sensory nucleus of V
VV
Spinal nucleus of V
Spinothalamic tract
Mesencephalic nucleus of V
CN V - TrigeminalCN V - Trigeminal
Motor - Muscles of masticationMotor - Muscles of mastication The The Motor nucleus of VMotor nucleus of V is homologous is homologous
to ventral horn in the spinal cordto ventral horn in the spinal cord Corticobulbar upper motor neurons Corticobulbar upper motor neurons
synapse on lower motor neurons synapse on lower motor neurons originating in this nucleusoriginating in this nucleus
CN V - TrigeminalCN V - Trigeminal
VV
Main sensory nucleus of V
VV Spinal nucleus of V
V V Motor nucleus of V
UMN
LMN
Mesencephalic nucleus of V
Clinical CorrelationClinical Correlation
Afferent limb of corneal blink reflexAfferent limb of corneal blink reflex Direct and consensual responseDirect and consensual response
Clinical CorrelationClinical Correlation
Jaw muscle weaknessJaw muscle weakness Jaw deviates toward the weak sideJaw deviates toward the weak side
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Clinical CorrelationClinical Correlation
Disorders of sensationDisorders of sensation Trigeminal neuropathyTrigeminal neuropathy Trigeminal neuralgiaTrigeminal neuralgia
Traumatic brain injuryTraumatic brain injury Loss of smell does not include harsh or Loss of smell does not include harsh or
unpleasant smellsunpleasant smells This can be a means of detecting This can be a means of detecting
“faking”“faking” Smelling salts and the ARASSmelling salts and the ARAS
CN VII - FacialCN VII - Facial
CN VII - FacialCN VII - Facial
Motor (branchial)Motor (branchial) Muscles of facial expression via the Muscles of facial expression via the
motor nucleus of VIImotor nucleus of VII Eye closureEye closure
Motor (autonomic)Motor (autonomic) To salivary and lacrimal glands from To salivary and lacrimal glands from
superior salivatory nucleussuperior salivatory nucleus
CN VII - FacialCN VII - Facial
Somatic sensorySomatic sensory Skin of the outer ear to spinal Skin of the outer ear to spinal
trigeminal nucleustrigeminal nucleus Visceral SensoryVisceral Sensory
Palate and taste buds on anterior 2/3 of Palate and taste buds on anterior 2/3 of the tongue to the Nucleus of the the tongue to the Nucleus of the solitary tractsolitary tract
CN VII - FacialCN VII - Facial
VII VII
Nucleus of the solitary tract
Superior salivatory nucleus
Motor nucleus of VII
CN VII - FacialCN VII - Facial
Motor nucleus of VIIMotor nucleus of VII Corticobulbar fibers for upper face Corticobulbar fibers for upper face
synapse on the motor nucleus of VII synapse on the motor nucleus of VII bilaterally (most fibers decussate)bilaterally (most fibers decussate)
Fibers bound for the lower face synapse Fibers bound for the lower face synapse on the contralateral nucleus onlyon the contralateral nucleus only
CN VII - FacialCN VII - Facial
VII VII
To upper face
To lower face
To upper face
To lower face
CN VII - FacialCN VII - Facial
VII VII
To upper face
To lower face
To upper face
To lower face
CN VII - FacialCN VII - Facial
VII VII
To upper face
To lower face
To upper face
To lower face
Clinical CorrelationClinical Correlation
Lesions of the cortex or corticobulbar Lesions of the cortex or corticobulbar tracttract Contralateral lower face weaknessContralateral lower face weakness Ex: StrokeEx: Stroke
Lesions of the motor nucleus of VII or Lesions of the motor nucleus of VII or peripheral nerveperipheral nerve Ipsilateral lower and upper face weaknessIpsilateral lower and upper face weakness Ex: Bell’s PalsyEx: Bell’s Palsy
Clinical CorrelationClinical Correlation
CN VII is the efferent limb of the CN VII is the efferent limb of the corneal blink reflexcorneal blink reflex
? - left
? - right VII - right
VII left
Clinical CorrelationClinical Correlation
Corneal blink reflexCorneal blink reflex Afferent fibers originate in the Afferent fibers originate in the
ophthalmic division of CN Vophthalmic division of CN V Synapse on Spinal Nucleus of VSynapse on Spinal Nucleus of V Internerons project bilaterally (via the Internerons project bilaterally (via the
reticular formation) to neurons in the reticular formation) to neurons in the motor nucleus of VIImotor nucleus of VII
Clinical CorrelationClinical Correlation
CN VII is the efferent limb of the CN VII is the efferent limb of the corneal blink reflexcorneal blink reflex
V - left
V - right VII - right
VII left
CN VIII CN VIII VestibulocochlearVestibulocochlear
CN VIII - CN VIII - VestibulocochlearVestibulocochlear
Two divisions - both special sensoryTwo divisions - both special sensory Cochlear (auditory)Cochlear (auditory) VestibularVestibular
CN VIII - CN VIII - VestibulocochlearVestibulocochlear
Cochlear divisionCochlear division Cochlear ganglion to CN VIIICochlear ganglion to CN VIII CN VIII synapses in the cochlear nucleiCN VIII synapses in the cochlear nuclei Cochlear nuclei project to the superior olivary Cochlear nuclei project to the superior olivary
nucleus and inferior colliculusnucleus and inferior colliculus Superior olivary nucleus is also receiving input Superior olivary nucleus is also receiving input
from contralateral cochlear nucleifrom contralateral cochlear nuclei Superior olivary nucleus projects to inferior Superior olivary nucleus projects to inferior
colliculuscolliculus Inferior colliculus projects to thalamusInferior colliculus projects to thalamus
CN VIII - CN VIII - VestibulocochlearVestibulocochlear
Cochlear divisionCochlear division
Cochlear Nuclei
VIII
Sup. Olivary Nuc.
Clinical CorrelationClinical Correlation
Note that auditory information is Note that auditory information is bilaterally represented very early in the bilaterally represented very early in the pathwaypathway
This means that you only have unilateral This means that you only have unilateral hearing loss followinghearing loss following Lesion to CN VIII itselfLesion to CN VIII itself Lesion to the cochlear nuclei on one sideLesion to the cochlear nuclei on one side
Cortical lesions (i.e., Heschel’s Gyrus) will Cortical lesions (i.e., Heschel’s Gyrus) will not result in unilateral hearing loss not result in unilateral hearing loss
CN VIII - CN VIII - VestibulocochlearVestibulocochlear
Vestibular division - inputsVestibular division - inputs Vestibular afferents project toVestibular afferents project to
The cerebellumThe cerebellum Vestibular Nuclear ComplexVestibular Nuclear Complex
InferiorInferior LateralLateral MedialMedial SuperiorSuperior
Vestibular Nuclear Complex also receives afferents Vestibular Nuclear Complex also receives afferents fromfrom
CerebellumCerebellum Contralateral Vestibular Nuclear ComplexContralateral Vestibular Nuclear Complex
CN VIII - CN VIII - VestibulocochlearVestibulocochlear
Vestibular division - inputsVestibular division - inputs
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CN VIII - CN VIII - VestibulocochlearVestibulocochlear
Vestibular division - OutputsVestibular division - Outputs ThalamusThalamus Nuclei of III, IV, and VINuclei of III, IV, and VI Spinal CordSpinal Cord
Lateral Vestibulospinal TractLateral Vestibulospinal Tract Medial Vestibulospinal TractMedial Vestibulospinal Tract
CN VIII - CN VIII - VestibulocochlearVestibulocochlear
Vestibular division - OutputsVestibular division - Outputs ThalamusThalamus Nuclei of III, IV, and VINuclei of III, IV, and VI Spinal CordSpinal Cord
Lateral Vestibulospinal TractLateral Vestibulospinal Tract Medial Vestibulospinal TractMedial Vestibulospinal Tract
CerebellumCerebellum
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CN VIII - CN VIII - VestibulocochlearVestibulocochlear
Medial and Lateral Vestibulocerebellar Medial and Lateral Vestibulocerebellar TractsTracts Part of a system that supports the voluntary Part of a system that supports the voluntary
motor system by providing corrective signals motor system by providing corrective signals to muscles depending on vestibular feedbackto muscles depending on vestibular feedback
Why are there projections to oculomotor Why are there projections to oculomotor nuclei?nuclei?
Clinical CorrelationClinical Correlation
Vestibuloocular Reflex (VOR)Vestibuloocular Reflex (VOR) Fixation of gaze despite head movementFixation of gaze despite head movement Stabilizes image on the retinaStabilizes image on the retina Reflexive, Reflexive, notnot a pursuit movement a pursuit movement Works in the darkWorks in the dark Works if unconsciousWorks if unconscious
Clinical CorrelationClinical Correlation
Doll’s eye maneuverDoll’s eye maneuver Can be used to test the integrity of the brain Can be used to test the integrity of the brain
stem in an unconscious patientstem in an unconscious patient
CN IX - GlossopharyngealCN IX - Glossopharyngeal
CN IX - GlossopharyngealCN IX - Glossopharyngeal
Glossopharyngeal means “tongue Glossopharyngeal means “tongue and throat”and throat”
Numerous afferents fromNumerous afferents from Carotid sinusCarotid sinus Walls of the pharynxWalls of the pharynx Mucous membranesMucous membranes Taste bud from posterior 1/3 of the Taste bud from posterior 1/3 of the
tonguetongue
CN IX - GlossopharyngealCN IX - Glossopharyngeal
SensorySensory Taste bud afferents travel to the Taste bud afferents travel to the
nucleus of the solitary tractnucleus of the solitary tract Pain from the pharynx and posterior 1/3 Pain from the pharynx and posterior 1/3
of the tongue likely go to spinal of the tongue likely go to spinal trigeminal nucleustrigeminal nucleus
Some sensory fibers likely reach the Some sensory fibers likely reach the main sensory nucleus of Vmain sensory nucleus of V
CN IX - GlossopharyngealCN IX - Glossopharyngeal
MotorMotor StylopharyngeusStylopharyngeus
Swallowing (with X anf XII)Swallowing (with X anf XII) Elevates the pharynx while swallowing and Elevates the pharynx while swallowing and
speakingspeaking These fibers arise from the These fibers arise from the nucleus nucleus
ambiguus, ambiguus, a poorly differentiated a poorly differentiated nucleus in the medullary tegmentumnucleus in the medullary tegmentum
Clinical CorrelationClinical Correlation
Afferent of the Gag ReflexAfferent of the Gag Reflex
CN X - VagusCN X - Vagus
Principal parasympathetic nervePrincipal parasympathetic nerve Widely distributed (vagus = Widely distributed (vagus =
“wandering”)“wandering”) Some overlap with CN IXSome overlap with CN IX Preganglionic parasympathetic fibers Preganglionic parasympathetic fibers
to the thoracic and abdominal viscerato the thoracic and abdominal viscera Arise in the dorsal motor nucleus of the Arise in the dorsal motor nucleus of the
vagusvagus Fibers to the heart originate in the Fibers to the heart originate in the
nucleus ambiguusnucleus ambiguus
CN X - VagusCN X - Vagus
Visceral sensory information fromVisceral sensory information from Thoracic and abdominal visceraThoracic and abdominal viscera Taste buds of the epiglottisTaste buds of the epiglottis Most project to nucleus of the solitary Most project to nucleus of the solitary
tracttract Some may project to spinal nucleus of VSome may project to spinal nucleus of V
Clinical CorrelationClinical Correlation Hoarseness (larynx)Hoarseness (larynx) DysarthriaDysarthria Paralysis of the soft palateParalysis of the soft palate DysphagiaDysphagia Uvula deviates away from weaknessUvula deviates away from weakness Loss of cough reflex (anesthesia of Loss of cough reflex (anesthesia of
pharynx and larynx)pharynx and larynx)
Clinical CorrelationClinical Correlation Efferent of the gag reflexEfferent of the gag reflex
IX X
Clinical CorrelationClinical Correlation Vagal nerve stimulatorVagal nerve stimulator
Implantable deviceImplantable device Treatment for seizuresTreatment for seizures
CN XI - Spinal AccessoryCN XI - Spinal Accessory
CN XI - Spinal AccessoryCN XI - Spinal Accessory
Motor only - neck and shoulder Motor only - neck and shoulder musclesmuscles SternocleidomastoidSternocleidomastoid Part of the trapeziusPart of the trapezius
Accessory Nucleus (cervical spinal Accessory Nucleus (cervical spinal cord)cord)
CN XII - HypoglossalCN XII - Hypoglossal
CN XII - HypoglossalCN XII - Hypoglossal
Motor - Muscles of the tongueMotor - Muscles of the tongue Hypoglossal NucleusHypoglossal Nucleus
Clinical CorrelationClinical Correlation
Which side of the tongue is weak?
Clinical CorrelationClinical Correlation
The tongue deviates to the weak side The tongue deviates to the weak side when protrudedwhen protruded
Coming Up…Coming Up…
DiencephalonDiencephalon ThalamusThalamus HypothalamusHypothalamus