David Jho

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NEUROANATOMY REVIEW

• David Jho

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CEREBRAL CTX
3
BRODMANNS AREAS
4
3,1,2
6
5,7
8
9
40
39
10
19
22
45,44
18
41,42
28
17
34
11
12
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BRODMANNS AREAS
8 Frontal Eye Field 6 SMA Premotor ctx
5,7 PPC (apraxia, dom. side) 4 Primary motor
ctx 3,1,2 Primary somatosensory ctx 41,42
Primary auditory ctx (Transverse gyrus of
Heschl) 45,44 Brocas speech area (Inf Frontal
Lobe expressive dysprosody) 22 Wernickes
speech area (arcuate fasciculus connect to
Brocas receptive dysprosody) 40
Supramarginal gyrus (Rt/Lt confusion,
dyscalculia, understanding speech) 39
Angular gyrus (dyslexia dysgraphia)
4
3,1,2
6
5,7
8
9
40
39
10
19
22
45,44
18
41,42
28
17
34
11
12
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BRODMANNS AREAS
39, 40 Inf parietal lobe (Gerstmanns syndrome)
on dominant side a) Rt/Lt confusion b)
dyscalculia c) finger agnosia d) dyslexia
dysgraphia e) lower quadrantanopia (visual
radiations to cuneus) Parietal lobe,
non-dominant hemisphere (Sup or Inf parietal
lobes) a) contralateral sensory neglect
astereognosis b) construction apraxia c) lower
quadrantanopia (visual radiations to
cuneus) 9,10,11,12 Prefrontal ctx Post part of
orbital gyrus smell Uncus serves as part of
primary olfactory ctx (medial temporal lobe) 34
Primary olfactory ctx (medial temporal
lobeseizures can have smell aura)
4
3,1,2
6
5,7
8
9
40
39
10
19
22
45,44
18
41,42
28
17
34
11
12
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LIMBIC SYSTEM
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PAPEZ CIRCUIT (Limbic System)
HIPP
Septal area
Hypothal
Fornix
Stria terminalis
VAFP/VAPP
Fornix
Ventral AmygdaloFugal Pathway Ventral
AmygdaloPetal Pathway
Mamillary body
Amygdala
Mamillothalamic tract
Olfactory, Sensory, Autonomic
Ant nuc of thalamus
Wernickes Encephalopathy (Thiamine/Vit B1
defic)
Ant limb of internal capsule
1) Nystagmus
2) Ataxia
3) Mental status change
Cingulate gyrus
Perforant pathway
Cingulum
Korsakoffs confabulatory syn
Entorhinal ctx
1) Mem loss confabulation
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Mediodorsal nuc of the thalamus (associated with
Ant nuc)
Orbitofrontal ctx (associated with HIPP)
Ansa lenticularis VA Fugal Pathway
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Klüver-Bucy Syndrome
(bilateral ablation of ant temporal lobes
including amygdala)

• Docility
• Hypersexuality
• Hyperphagia
• Visual agnosia

AMYGDALAcoordinates behavioral emotional
responses to complex sensory input by integrating
somatosensory and viscerosensory
information. Output via Stria Terminalis
posteriorly by tail of caudate and arches over
thalamus to anterior hypothalamus. Output via
Ventral Amygdalofugal pathway (VAFP) to
Caudate/Septal Area.
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HYPOTHALAMUS

• Homeostasis (autonomic, endocrine, limbic
  systems)
• Half of hypothalamus is enough

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Ant Hypothal Nuc
(dissipates heat,
parasympathetic)
Preoptic area
(Medial Preoptic Nuc)
(sexually dimorphic,
regulates gonadotropic
hormones)
Suprachiasmatic nuc (direct retinal input,
circadian rhythms)
Lat Nuc
(appetite center, stim
induces eating, destruction causes starvation)
Dorsomedial Nuc
(stim causes obesity savage
behavior)
Ventromedial Nuc
(satiety center,
stim stops eating, destruction causes obesity
savage behavior)
Arcuate Nuc
(DOPA-ergic neurons inhib prolactin
release) TUBERO-
INFUNDIBULAR
TRACT
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HYPOTHALAMIC FIBER SYSTEMS
Fornix
From HIPP to mamillary nuclei (then
Mamillothalamic tract to Ant Thal Nuc)
Medial Forebrain Bundle (MFB)

• in lat hypothalamus, lat to fornix can be
  damaged in hypothal injury
• unmyelinated, major connection b/n cerebral ctx
  BS
• no synaptic relay through thalamus
• has monoaminergic neurons from the locus
  coeruleus (NE), raphe nuclei
  (5-HT), and ventral tegmental area (DA).

Hypothalamo-spinal tract
Descending autonomic fibers for sympathetic
neurons (thoracic intermediolateral horn) and
parasympathetic neurons (sacral lateral
horn) Lesion or interruption above T1 can cause
Horners syndrome (miosis, ptosis, anhidrosis,
apparent enophthalmos)
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HYPOTHALAMIC FIBER SYSTEMS
Stria terminalis
Stria terminalis is the major pathway of Amygdala
to hypothalamus septal area. STRIA STRANDS
(Sup to fornix divides caudate from
thalamus) Lamina terminalis (from optic chiasm to
rostral 3rd ventricle closure of ant neuropore)
LAMINA LAYER Stria medullaris thalami
(hypothalamus septal area in roof of 3rd
ventricle inf to fornix to thalamus epithalamic
habenular nuclei relay from limbic forebrain to
midbrain reticular formation) MEDULLARIS is also
in the MEDULLA Stria medullaris of 4th ventricle
(central sulcus to Inf Cereb Ped arcuate nuc of
pyramids) Sulcus Limitans (divides Alar Basal
plates) SULCUS GROOVE
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HYPOTHALAMIC FIBER SYSTEMS
(strands)
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HYPOTHALAMIC FIBER SYSTEMS
Ant neuropore (anencephaly) vs
Post
neuropore (spina bifida)
Lamina terminalis (layer)
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HYPOTHALAMIC FIBER SYSTEMS
(medial also in medulla)
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HYPOTHALAMIC FIBER SYSTEMS
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EMBRYOLOGIC DEVELOPMENT
Neural Tube (CNS, pregang ANS)
Neural Crest (PNS including DRG, postgang

ANS)
Sulcus Limitans (divides Alar Basal plates)
Alar plate (sensory), Basal plate (motor)
Rhombencephalic lip (in roof of 4th ventricle
becomes Cerebellum)
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EMBRYOLOGIC DEVELOPMENT
SECONDARY VESICLES
PRIMARY VESICLES
Telencephalon (lateral ventricles)
Prosencephalon
Diencephalon (3rd ventricle)
Mesencephalon
Mesencephalon (cerebral aqueduct)
Metencephalon (upper 4th ventricle)
Rhombencephalon
Myelencephalon (lower 4th ventricle, central
canal)
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THALAMUS
BLOOD SUPPLY
1. PCA (post circulation)
2. PCOM
(ant circulation)
3. Ant Choroidal a (ICA)
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ANT-MED (limbic)
ANT-LAT (EPS)
POST (sensory)
NON-SPECIFIC (relay)
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VA/VL (GPSN) AntMD (Papez) VPL
(sensory--body) VPM (sensory--head) LGN
(vision) MGN (hearing) Pulvinar (visual sensory
association) Intralaminar CM (very diffuse to
cerebral ctx, ends in layer I for cortical
excitability) Reticular (GABA-ergic to thal)
ANT-MED (limbic)
ANT-LAT (EPS)
POST (sensory)
NON-SPECIFIC (relay)
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Mamillary bodies
Cingulate gyrus
Prefrontal ctx
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GP, SN (EPS)
Area 6
Area 4
GP, SN, cerebellum (EPS dentatothalamic
tract)
Area 4 EPS
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Integration of somesthetic, visual, auditory
Areas 18,19
Areas 3,1,2
Areas 41,42
Sensory--body
Hearing
Sensory--face
Vision
Area 17
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LD or DL
LP
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HIPPOCAMPUS
HIPPOCAMPAL FORMATION (3-layered archicortex
declarative mem)
a) Dentate gyrusHIPP
input output to HIPP pyramidal cells

b) Hippocampus proper or Cornu Ammonis
(CA)to fornix then septal area
c) Subiculumto fornix then
mamillary nuc
Alzheimers Disease affects neurons in Nuc
Basalis of Meynert (ACh), Locus Coeruleus (NE),
Entrorhinal ctx, and CA1/Subiculum of HIPP.
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HIPPOCAMPUS
Mammillary bodies
Postcommissural Fornix
Fimbria of Fornix
(connects bilateral CA)
Alveus
6-layer NEOCORTEX
3-layer ARCHICORTEX
vs
Schaeffer collaterals
CA3
CA1
CA4
DENTATE GYRUS
Perforant path
Entorhinal ctx (with pyriform ctx are
paleoctx)
SUBICULUM
Alvear path
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Dentate gyrus has afferents entirely within HIPP
formation. CA1 projects to Subiculum and
precommissural fornix. CA3 projects to CA1 and
precommissural fornix. CA4 (hilus of dentate
gyrus) receive afferents from dentate and project
to bilateral dentate (hippocampal
commissure). Subiculum provides main efferents to
POST-COMMISSURAL FORNIX (to thalamus and
hypothalamus).
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EPS SYSTEM
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Pyr system (CS tract)
UMN lesion
LMN lesion
1. Weakness 2. Spasticity 3. Inc tone
4. No atrophy 5. Babinski
1. Weakness 2. Dec DTR
3. Dec tone 4. Atrophy
5. Downgoing toes
Cerebellum
EPS (Basal Ganglia)

• Intention tremor
• Ataxia (fall towards lesion, gait trunk
  dystaxia, dysrhythmokinesia,
  dysdiadochokinesia, dysmetria)
  
• Nystagmus
  
• Dec DTR/tone ipsilaterally
  
• Asthenia (mm tire easily)

• Chorea (Huntingtons, Syndenhams)
• Athetosis (choreoathetosis in HD, Tardive
  dyskinesia when antipsychotics block DA receptors
  make super-sensitive)
• Hemiballismus (stroke)
• Parkinsons vs Diffuse Lewy Body Dz (resting
  tremor, bradykinesia, truncal instability,
  dementia)

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Lenticular nuc Put GP
Striatum/Neostriatum Put Caud Corpus
striatum Put Caud GP
Glutamate
GABA
(Glycine in SC)
Input from Ctx--Net excitation
Input from D1 recepNet
excitation
DIRECT PATHWAY
Ctx
Striatum
GPi/SNr
VA/VL thalamus
Ctx
Parkinsons
D1 recep
SNc
Input from CtxNet inhibition
Input from D2 recepNet excitation
INDIRECT PATHWAY
Ctx
Striatum
GPi/SNr
VA/VL thalamus
Ctx
GPe
STN
Parkinsons
D2 recep
SNc
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Striatum (GABAergic neurons) have both D1 recep
(Gs contain excitatory Substance P) and D2 recep
(Gi contain inhibitory Enkephalin).
Net LOSS of excitation in Parkinsons Dz.
Pallidotomy destroys segments of GPi to reduce
inhibition of thalamus (interrupts direct
indirect pathways). GPi and GPe are usually
always on.
Input from Ctx--Net excitation
Input from D1 recepNet
excitation
DIRECT PATHWAY
Ctx
Striatum
GPi/SNr
VA/VL thalamus
Ctx
Parkinsons
D1 recep
SNc
Input from CtxNet inhibition
Input from D2 recepnet excitation
INDIRECT PATHWAY
Ctx
Striatum
GPi/SNr
VA/VL thalamus
Ctx
GPe
STN
Parkinsons
D2 recep
SNc
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GPe is constantly on. In Huntingtons chorea,
the striatum (ACh GABAergic medium spiny
neurons) are destroyed so GPe overstimulates Ctx.
Damage to STN results in Hemiballismus due to
decreased stim of thalamic inhibition to Ctx.
Input from Ctx--Net excitation
Input from D1 recepNet
excitation
DIRECT PATHWAY
Ctx
Striatum
GPi/SNr
VA/VL thalamus
Ctx
Parkinsons
D1 recep
SNc
Input from CtxNet inhibition
Input from D2 recepnet excitation
INDIRECT PATHWAY
Ctx
Striatum
GPi/SNr
VA/VL thalamus
Ctx
GPe
STN
Parkinsons
D2 recep
SNc
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CEREBELLUM
Functional vs Anatomical Divisions
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Cerebellar Synonyms

• FLOCCULONODULAR LOBE Vestibulocerebellum.
• VERMIS Medial zone or part of Spinocerebellum.
• PARAVERMIS Intermediate zone or part of
  Spinocerebellum.
• CEREBELLAR HEMISPHERES Lateral zone or
  Cerebrocerebellum or Pontocerebellum.

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Cerebellar Function

• FLOCCULONODULAR LOBE balance eye movement.
• VERMIS balance axial motor functions.
• PARAVERMIS distal motor execution.
• CEREBELLAR HEMISPHERES motor planning.

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Cerebellar Peduncles
1. Sup Cerebellar Ped (dentatothalamic tract,
VSCT) 2. Middle Cerebellar Ped (pontocerebellar
fibers) 3. Inf Cerebellar Ped (OlivoCT, Dorsal
SpinoCT, CCT, vestibulocerebellar tract) - Spine
to cerebellum
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Motor Ctx (corticopontine CS tracts)
VL (thalamus)
Corticopontine fibers
MOLECULAR LAYER
Basket
Stellate
Pontine nuc
Dentatothalamic tract (Sup Cereb Ped)
Red Nuclei (rubrospinal tract)
Pontocerebellar tract
(contralat)
PARALLEL FIBERS
PURKINJE LAYER
Cereb Deep Nuc Dentate Emboliform Fastigial Globos
e
Purkinje
MOSSY FIBERS
GOLGI LAYER
CLIMBING FIBERS
Golgi
Spinocerebellar Pontocerebellar Vestibulocerebella
r (cerebellar vestibular nuc)
Granule
ION
Olivocerebellar tract to CLIMBING FIBERS
Vestibulospinal tract
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4 Cerebellar Deep Nuclei
5 Types ofCerebellar Cells (know if excit or
inhib know if projects out of cerebellum or not)
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Cerebellar Deep Nuclei receive excitatory
afferents from Climbing fibers and Mossy fibers
(collaterals on their way to the Granule layer).
Purkinje cell (only ones that project out of ctx)
inhibitory fibers from Cerebellar Ctx to
Cerebellar Deep Nuclei. Climbing fibers from Inf
Olivary Nuc via Inf Cerebellar Ped.
Pontocerebellar fibers via Middle Cerebellar Ped.
Granule cell (only excitatory) endings (Parallel
Fibers) go to Molecular layer but not out of
Cerebellar Ctx. Stellate, Basket, Golgi cells
(inhibitory) do not project out of Cerebellar Ctx
either.
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Flocculo-nodular lobe projects to Medial and
Lateral Vestibular Nuclei.
Medial Vestibular Nuclei assist coordinating eye
movement with body.
Lateral Vestibular Nuclei assist postural control.
Be careful not to confuse Dentate nuclei
(cerebellum) and Dentate gyri (HIPP).
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Rubrospinal tracts (gross mvmts unlike CS tracts)
crosses immed in midbrain.
Rt cerebellum to Lt Red Nucleus to Rubrospinal
tracts crossing left-to-right to innervate Rt arm
leg.
Cerebellar tests finger-to-nose (dysmetria
intention tremor), foot tap/heel shin, pronator
drift with poor adjustment, dysdiadochokinesia,
nystagmus on extreme gaze.
Romberg test vision, vestibular, DC-ML. (not SC
tract, which is unconsc proprio).
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BVs CNs
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Berry aneurysms (ACOM, MCA, PCOM, basilar)
asymptomatic unless large or rupture (possible
death)
ruptureSAH, hemorr stroke (seizures, HCP)
worst HA of life (10/10)
ADPKD, Ehlers-Danlos, Marfans
Uncus where Amygdala is located
Pituitary adenoma
Acoustic neuroma (Schwannoma) at CPA
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ICA-MCA aneurysm can put pressure on side of
optic chiasm.
Basilar tip aneurysm can put pressure on CN3s.
Lat striate or Lenticulostriate aa of cerebral
hemorrhage (internal capsule).
Occlusion of PCA distal to PCOM can result in Ant
choroidal to Post choroidal aa.
Labyrinthine a from AICA or Basilar a. Post
Spinal a from PICA or Vertebral a.
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Autoregulation allows constant blood flow over
wide bp range (local metabolite control).
Pupillary light reflex is CN2 afferent and CN3
efferent.
CN2 lesion preserves a consensual reflex. CN3
lesion causes blown-pupil, down-and-out eye,
droopy eyelid, efferent loss.
Corneal blink reflex is CN5 (V1) afferent and CN7
efferent.
Ankle jerk S1 Knee ext
L2,3,4 Brachiorad C5 Biceps
C6 Triceps C7 Abdominal
T8-T12 Babinski L5-S1
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Internal Capsule
BLOOD SUPPLY
ANT LIMB ACA (medial striate aa) MCA
(lateral striate aa) GENU ICA (Ant Choroidal
a) POST LIMB ICA (Ant Choroidal a) MCA
(lateral striate aa)
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Epidural lens,
Subdural falx, Subarachnoid
(ventricles), Intraparenchymal
bleeds
Scalp infections down through valveless emissary
vv.
Pineal tumors (Perinauds syn) block cerebral
aqueduct and/or impose on sup colliculus
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HCP ex-vacuo (big ventricles, no inc ICP)
Pseudotumor cerebri (nml or slit ventricles,
inc ICP)
Communicating vs Non-communicating
Hydrocephalus (HCP)
Above or below 4th ventricle
Choroid plexus Creates CSF, Arachnoid
villi/granulations Absorb CSF
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HERNIATION SYNDROMES
Subfalcine Transtentorial Foraminal
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VISUAL SYSTEM
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NASAL
TEMPORAL
TEMPORAL
Ipsilateral blindness
Nasal hemianopia
Contralateral hemianopia with macular sparing
Bitemporal hemianopia
to LGN, optic radiations, then
occipital lobe
Contralateral hemianopia
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LGN
Crossed fibers to layers 1, 4, 6
Uncrossed fibers to layers 2, 3, 5
to LGN, optic radiations, then
occipital lobe
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LGN
Crossed fibers to layers 1, 4, 6
Uncrossed fibers to layers 2, 3, 5
to LGN, optic radiations, then
occipital lobe
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LGN to OCCIPITAL LOBE
Parietal lobe visual radiations to cuneate gyrus
Contralateral lower quadrantanopia
Calcarine fissure
Temporal lobe visual radiations (Meyers loop) to
lingual gyrus
to LGN, optic radiations, then
occipital lobe
Contralateral upper quadrantanopia
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Constricted field (glaucoma)
Central scotoma (optic neuritis in MS)
Lower altitudinal hemianopia (bilateral cuneate
gyri)
to LGN, optic radiations, then
occipital lobe
Upper altitudinal hemianopia (bilateral lingual
gyri)
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Sup Colliculus
Vertical gaze
MLF
Coordinates CN3 CN6
(internuclear ophthalmoplegia in MS)

• carries info from pontine Horizontal Gaze Centers
  to oculomotor complex in midbrain.
• Inc activity during mvmt
• Helps during turning of head (conjugate gaze)

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Left?
Right?
to LGN, optic radiations, then
occipital lobe
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Right?
Left?
True Diplopia
CN3 accommodation, many mvmts
CN4 down-and-out
CN6 lateral
to LGN, optic radiations, then
occipital lobe
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Voluntary Conjugate Gaze
Lt Medial Longitudinal Fasciculus (MLF)
Rt Pontine Paramedian Reticular Formation (PPRF
lat gaze center)
Lt Area 8 (FEF)
Rt CN6
Lt CN3
Rt Gaze
Pupillary Light Reflex
Optic n/chiasm/tract (CN2)
Sup Colliculi (pretectal area)
Ciliary ganglia (CN3)
LGB
Accommodation
Optic n/chiasm/tract (CN2)
Sup Colliculi (pretectal area)
Optic radiation
Ciliary ganglia (CN3)
Visual ctx
LGB
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Voluntary Conjugate Gaze
Lt Medial Longitudinal Fasciculus (MLF)
Rt Pontine Paramedian Reticular Formation (PPRF
lat gaze center)
Lt Area 8 (FEF)
Rt CN6
Lt CN3
Rt Gaze
Pupillary Light Reflex
Optic n/chiasm/tract (CN2)
Sup Colliculi (pretectal area)
Ciliary ganglia (CN3)
LGB
Accommodation
Optic n/chiasm/tract (CN2)
Sup Colliculi (pretectal area)
Optic radiation
Ciliary ganglia (CN3)
Visual ctx
LGB
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HEARING

• Medial Superior Olive (SON) is 1st place with
  binaural processing.
• Lesion above cochlear nuclei (Lateral leminscus
  and up) will decrease hearing bilateral (more in
  contralateral ear).
• Inner hair cells transduce sound, and Outer hair
  cells modify sound (olivocochlear efferents).
  Scala media (endolymph).
• Lateral Superior Olive (SON) has intensity
  differences for horizontal position orientation.
• High freq is closest to Oval window/Stapes (scala
  vestibule and NOT round window at the end of the
  scala tympani) for tonotopic organization, and
  high freq is dorsomedial in cochlear nuclei.

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HEALING

• ANTEROGRADE degeneration is Wallerian
  degenerationaxons myelin sheaths disappear.
  (e.g., Mid-thoracic crush of spine and Pt dies.
  Cervical stain shows Wallerian degeneration of
  fasciculus gracilis.)
• RETROGRADE degeneration is Chromatolysisloss of
  Nissl substance (RER free polyribosomes at cell
  body and dendrites are lost)
• In the CNS, glial scars formed by astrocytes
  inhibit healing (reactive astrogliosis).
• For successful axonal repair, macrophages must
  clean debris.
• 5. Axonal elongation is 2-4 mm/d in the CNS
  (oligodendrocytes) or PNS (Schwann cells).

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HEALING

• 1. Target-derived neurotrophic factor Nerve
  Growth Factor (NGF) tropic (differentiation
  turning toward stim) trophic (growth
  survival) peptide for DRG and sympa in PNS and
  basal forebrain ACh neurons in CNS.
• Neurotrophins (NGF, BDNF, NT3) IGF1 FGF
  GDNF CNTF
• BDNF is synthesized in cell body transported
  anterogradely down the axons (unlike NGF or
  GDNF).

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Neurohistology
Sensory neurons Pseudounipolar, myelinated
(DRG and CN 5, 7, 9, 10) Special senses
Bipolar (smell is unmyelinated-slow, hearing is
myelinated-fast) (CN 1, 2, 8) Motor
neurons Multipolar, myelinated (aMN, ANS)
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6-Layered Neocortex
Layer I (Molecular) Layer II (External
Granular) Layer III (External Pyramidal)cortico-c
ortical fibers Layer IV (Internal
Granular)thalamocortical fibers (VPL, VPM,
LGN) Layer V (Internal Pyramidal)CS, CB,
corticostriatal fibers (Betz giant
pyramidal cells) Layer VI (Multiform)corticothala
mic projection association fibers
AFFERENT (Layer IV is big
in Brodmann Area 3,1,2)
EFFERENT (Layer V is big in
Brodmann Area 4)
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SENSORY MOTOR HOMUNCULI
Lots to lips, tongue, hand, index
finger Paracentral lobule feet/legs
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RABIES
Rabies is caused by a Rhabdovirus that enters a
peripheral nerve and travels retrograde up the
nerve to the DRG. From there, it replicates and
infects the CNS, resulting in encephalitis with a
variety of neurologic symptoms leading to coma
and respiratory or cardiac arrest.
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THE END