
Brainstem
·
Cortical
fibers synapse directly on V, VII, NucAmb, XII (NOT on III,IV,VI,DMNX)
·
Corticobulbar
fibers bilateral except to lower VII (contra) & XII.
I (Olfaction)
·
SVA.
·
1° receptor cells (= bipolar cells) in mucosa,
axons form olfactory nerve, through cribiform plate > 2°:
mitral & tufted cells (= glomeruli) in bulb, (also has granule cells – no
axons, inhibitory); > Olf. Tract >
1.
Lateral olfactory stria: to anterior
olfactory nuc. (aka olfactory tubercle, > medial forebrain bundle and stria
medullaris), amygdala, and pyriform
cortex (=primary, area 34, > entorhinal cortex (=secondary), DM thalamus,
prefrontal cortex (conscious perception, input from pyriform and DM thalamus)),
or
2.
Medial olfactory stria > septal
area, anterior commisure to contralateral areas
·
Olfactory tubercle neurons project to
directly, not to olfactory tract/bulb
·
In mucosa: sustenacular cells support,
basal cells are receptor precursors – olfactory neurons are only ones to
continually regenerate.
·
There
are >2000 different receptor cells for odorants. Use G-proteins > cAMP or
IP3. 2 specific glomeruli in bulb for each odorant.
·
Accessory
olfactory system: For
detection of pheromones, rudimentary in humans. Vomeronasal organ >
vomeronasal/ terminal n. (“13th cranial nerve, CN0”) > accessory
olfactory bulb > Vomeronasal nucleus in amygdala. Contain GnRH cells –
related to GnRH cells in hypothalamus, mediates sexual dimorphism
·
CN0
has Schwann cells > schwannoma
II Optic
·
CNS tract – has oligodendroglial, not
Schwann cells.
·
SSA.
·
(rods/cones) > bipolar cells (1°)
> ganglion cells (2°)
> 3°
centers:
1.
LGB > visual cortex (conscious
vision) or
2.
Pretectal/EW nuclei (pupillary reflex,
see below) or
3.
Superior colliculi (> tectopontine
(> cerebellum) & tectospinal tracts; pursuit, head/neck mvmt) or
4.
suprachiasmatic nucleus of
hypothalamus (circadian rhythms)
Retina
·
Part of CNS – has blood-retina barrier
& Muller glia.
Receptor
cells: rods/cones.
·
Rhodopsin
(rods) > transducin (G-protein) > PDE > cGMP to GMP > ¯
Na & Ca current (hyperpolarizing) > ¯
glutamate release to bipolar cells (> “on-center” cells stimulated,
“off-center” cells inhibited, “on-center” bipolar cells stimulate its ganglion
cells and inhibit ganglion cells from “off-center” bipolar cells also);
·
Rods = B/W, dim light. Cone = color,
daylight. Both Use glutamate.
·
Conduct by electric conduction, not
action potentials.
Ganglion
cells
·
Only cells in retina that can initiate
action potential.
·
Types:
o
W = small,
slow, tonic & phasic to SC & pretectum, dark;
o
X (or P)
= medium sized, tonic, to layers 3-6 LGB
& pretectum, color; parvocellular stream;
o
Y (or M)
= rapid, phasic to layers 1&2 LGB & SC, B&W, magnocellular stream;
Horiztontal
cells: Synapses from & to depolarize rods/cones
for lateral inhibition
Amacrine
cells: Bipolar > Amacrine > Ganglion cells
Fovea
(center of macula) contains only cones. Rod goes to amacrine cell before
ganglion cell.
Lateral Geniculate Body (LGB)
·
Ipsilateral layers 2,3,5.
Contralateral layers 1,4,6.
·
Layers 1&2 magnocellular, 3-6
parvocellular,
·
3&4 off-center, 5&6 on-center
(1&2 mixed).
·
Ganglion cells and LGB cells have
“on-center, off-surround” concentric fields.
Cortex
·
Primary:
Area 17
o
Layer IVCa
= magnocellular input, layers IVCb & IVA = parvocellular input,
o
Layer IVB = cortical input, has stripe
of Genarri
·
Secondary:
Areas 18 (±19)
(no stripe of Gennari).
·
No concentric fields, cells repond to
lines, borders.
o
Simple
cells = position & orientation of line,
rectangular fields.
o
Complex
cells = orientation, movement (not position in
field).
o
Hypercomplex
cells = length, shapes.
·
Ocular
dominance columns in cortex alternate eye dominance, have orientation & location specificity.
o
Together strips form ocular dominance bands.
o
Absent in 2 areas of area 17: those
representing blind spot of retina & monocular temporal crescent.
o
Orientation
columns also exist.
o
Hypercolumn:
2 adjacent columns w/same field from each eye.
·
Magnocellular
stream: “where stream”.
o
Y-cells > Layer 1/2 LGB > area
17 (layer IVCa)
> parietal cortex.
o
Spatial, movement, orientation (visual
neglect, apraxia).
·
Parvocellular
stream: “what stream”
o
X-cells > Layer 3-6 LGB > area
17 (layers IVCb
& IVA) > inferior temporal.
o
Color, shape (faces, etc. visual
agnosias, achromotopsias)
Superior colliculi:
lesion gives loss of pursuit (tracking) eye movement
Blindsight:
nonconscious response to visual stiumli (ie threat) – from noncortical
projections, superior colliculus
III
Oculomotor
·
GSE to extraocular mm:
·
Levator palpebrae:
Mullers muscle = sympathetic, less severe ptosis
·
Parasymathetics (GVE):
EW to short ciliary nn. (sympathetic = long &
short) to iris (constriction) and ciliary mm. (accomodation).
·
Accomodation:
Ganglion cells(2°)
to LGB to cortex to (directly and indirectly) EW & CN3 (motor) nuclei (not
to pretectal nuclei) to Ciliary muscles (meridional and circular fibers)
o
Causes eyeball to narrow, lens to relax
and become more spherical for accommodation
·
Pupillary light reflex:
no LGB. (1°)
bipolar cells in retina to (2°)
ganglion cells to (3°)
pretectal nuclei to (4°)
EW nuclei (via posterior commisure) to (5°) ciliary ganglion to short ciliary nerves to
iris
·
Sympathetics
to pupil: 1° hypothalamus > via
hypothalamospinal tract > 2° C8-T3 lateral horn (Ciliospinal
center of Budge) > 3°
superior cervical gangion > around
·
Runs
between the PCA and SCA
IV
Trochlear
·
GSE
·
Superior Oblique > eye down &
In; only crossed n.;
·
Lesion: worst = downgaze to opposite
side.
·
Bielschowskys sign:
head tilted to opposite side; eye up & in. Difficulty walking down stairs.
·
V1 = ophthalmic > SOF >
nasociliary & lacrimal nn.
·
V2 = maxillary > inferior orbital
fissure or foramen rotundum.
·
V3 = mandibular > foramen
ovale.
·
Motor (SVE):
Motor nucleus of V (pons) > tensor palatini & tympani (hypoacusis),
mastication (temporalis, masseter, pterygoids, anterior belly of digastric,
mylohyoid). Weakness causes deviation of jaw away.
·
Sensation (GSA):
o
V1,2,3 > Trigeminal
(aka Semilunar, Gasserian) ganglion (1°) > spinal tract of CNV > principal sensory nucleus (2°,
touch, wide range of pressure, large receptive fields, in pons) and spinal nuclei of V (2°,
pain/temp, in medulla down to C2).
§ Trigeminal
Ganglion is in Meckle’s Cave
o
Mesencephalic
nucleus: proprioception, pressure. Contains 1°
neurons (only
nucleus in CNS w/1°
sensory neurons, from neural crest, analogous to sensory ganglia).
·
Tracts:
o Ventral
trigeminothalamic =
pain, crossed (from principal sensory & spinal).
o Dorsal = touch, uncrossed (principal sensory
only).
o Both to VPM.
VI
Abducent
·
GSE.
·
Lateral Rectus.
·
Longest CN.
·
Nerve
lesion causes unilateral lateral gaze
paralysis. Nuclear lesion causes
deviation away bilaterally (i.e. of
both eyes), gaze toward lesion is paralyzed (opposite of frontal eye fields)
called “lateral gaze paralysis”
·
PPRF –
horizontal gaze center adjacent to CN6 nucleus.
o
Inputs from cortex (FEFs), cerebellum,
SC, & vestibular nuc.
o
Output to cerebellum, vestibular nuc., pretectal region, IN of Cajal & Nuc. of
Darkshevich to integrate horizontal & vertical eye movement
·
Stimulation: rostral = vertical gaze;
caudal = ipsilateral horizontal.
VII
Facial
·
Geniculate ganglion: sensory/ taste
cell bodies only.
·
Nervus
intermedius carries sensory & parasympathetic
fibers.
Parasympathetics (GVE):
Input from hypothalamus & solitary nuc.
1.
Superior salivatory nuc. (1°)
> greater petrosal n. > pterygopalatine gang. (2°)
> lacrimal gland
2. Superior salivatory nuc. (1°) >chorda tympani >
submandibular gang. (2°)
> submandibular, sublingual glands.
·
Lesion
distal to geniculate ganglion has no decreased lacrimation, greater petrosal n.
already off
Motor (SVE): Facial
nucleus > staepedius (hyperacusis), stylohyoid, posterior belly of digastric
(anterior from CN5), facialmm. (part of motor nucleus
supplying lower face receive crossed input only from cortex)
Taste (SVA):
Anterior 2/3 tongue. Chorda tympani > geniculate ganglion (1°)
> rostral nucleus solitarius (2°) > central tegmental tract > VPM
thalamus (±
parabrachial nuc. of pons) > insular cortex (perception) (parabrachial >
amygdala/ hypothalamus for emotional response)
·
Sweet (sucrose), bitter (alkaloids),
& umami (glutamate) receptors are metabotropic, sour (H+) & salty (Na)
are ionotropic. (Spicy-hot mediated by trigeminal nerve)
·
Receptors may respond to multiple
tastes, but usually 1 preferentially.
Sensation: ear (GSA),
soft palate (GVA) > spinal nuc of V
Mobius
syndrome: congenital absence of both facial nuclei (±
abducens nucleus)
VIII
Auditory
·
SSA
·
BAER:
I°
cochlear n. > II°
cochlear nuc > (via trapezoid body) > III° Superior olive > IV°
lateral lemniscus/ nucleus > V° Inf. Colliculus > VI°
MGB > VII°
Cortex
·
Dorsal cochlear neurons bypass Sup
olive & lateral lemniscus nuc, to Inf Coll (III°)
·
Lesions above trapezoid body cause
partial deafness (contra > ipsilateral)
·
Commisure
of Probst: in between
lateral lemniscus nuclei. Also has Inferior Colliculi commissure.
Cochlea:
·
Sound enters scala vestibuli,
transmitted to scala media by Reissner’s membrane.
·
Hair cells in scala media (organ of
Corti) sit on basilar membrane, touch tectorial membrane; sit in endolymph
(high K, low Na).
·
Vibrations at apex have lower
frequency.
·
Scala vestibuli & tympani contain
perilymph, communicates w/CSF.
·
Cochlear nerve (bodies in spiral
ganglion) synapse on hair cells.
Cochlear nuclei:
·
Fibers group into 3 acoustic striae:
ventral, dorsal (from respective nuclei) & intermediate (from both). Dorsal
= high frequency, ventral = low. Ventral to superior olive, dorsal direct to
inferior colliculus.
Superior olive:
·
Attenuates loud sounds.
·
Input is from contralateral cochlear
n. via trapezoid body;
·
Output is via olivocochlear bundle
back to contralateral cochlea directly to hair cells to ¯
sensitvity to sounds and to tensor tympani (V3) and stapedius (7)
·
Medial Sup. Olive = time differences
·
Lateral Sup Olive = intensity
difference
Trapezoid body
is only commissure needed for sound localization
Cortex:
·
AI = area 41, A2 = area 42.
·
Area 22 = auditory association area.
·
Wernickes = posterior area 22.
·
Prosody = Right opercular (posterior
temporal =- comprehension of prosody)
·
Utricle > superior vest ganglion >
Lateral vestibuluar nucleus
·
Saccule:
o Posterior part > inferior vest
ganglion > inferior vestibular nucleus.
o Anterior part >
·
Detect
linear movement: utricle in long axis of body, functions when upright; saccule
in dorsoventral plane, fuctions when supine.
·
When
head is erect: utricle is horizontal, saccule vertical.
·
Sensation
occurs in macula – contain otoliths & hair cells.
Semicircular canals: Angular movement. Ampulla (dilation at 1 end)
contains endolymph and crista ampullaris – sensory organ). Fluid remains still
but hair cells move.
Vestibular
nuclei:
·
Lateral:
(Dieter’s) from utricle ( & anterior saccule?) to lateral vestibulospinal
tr. – extensor tone/posture; inhibited by anterior lobe of cerebellum; has no
connections w/other nuclei;
·
Inferior:
from posterior saccule to cerebellum; integrates input from vestibular
labyrinth & cerebellum;
·
Medial:
largest, crossed to all extraocular
nuclei & cerebellum, medial vestibulospinal tract to neck mm.;
·
·
Interstital:
cells lie among fibers of vestibular root
MLF:
·
Ascending:
from medial & superior vestibular nuclei to CN 3,4,6
nuclei to control eye movement.
·
Descending: medial vestibulospinal tract & medial
reticulospinal tract to cervical cord motorneurons to influence head/trunk
movements relating to eye & vestibular movement (from superior colliculus,
Caloric
nystagmus: COWS =
fast phase, deviation is reverse
Postrotatory nystagmus:
Slow phase in direction of rotation, fast phase opposite
IX
Glossopharyngeal
Motor (SVE):
Nuc. Ambiguus > stylopharyngeus
Parasympathetic (GVE):
Inf salivatory nuc > tympanic n./plexus > lesser
petrosal n. > otic gang. (2°)
> parotid
Sensation (GSA):
middle ear (tympanic n.), pharynx > Superior Gangion (1°)
> Spinal Nuc of V
Carotid Sinus (GVA):
Herrings n. > CN9 > Inferior Ganglion (1°) > nucleus solitarius (2°)
> DMN of X (
BP decreases HR, TPR, force, BP, CO)
Carotid Bodies (SVA):
Chemoreceptor (CO2) > Inf Ganglion > Reticular
Formation > Reticulospinal fibers > inspiration.
Taste (SVA):
nuc. Solitarius > VPM thalamus > postcentral gyrus
X
Vagus
Motor (SVE):
nuc. Ambiguus > pharyneal br. (all mm except stylopharyngeus (IX) and tensor
veli palatini (V)) > sup. Laryngeal n. > internal (sensory) &
external laryngeal (cricothyroid)
Recurrent laryngeal=(off
ganglion)all laryngeal except cricothyroid
Taste (SVA):
> solitary nuc.
Aortic sinus (GVA)
Inf ganglion > solitary nuc.
Aortic Bodies (SVA): > Inf Ganglion
> Reticular Formation
Parasympathetic (GVE):
dorsal motor nuc.
Sensory (GSA):
ear > spinal tract 5.
XI
Accessory
·
SVE.
·
C1-6, to trapezius, SCM
XII
Hypoglossal
·
All tongue mm. except palatoglossus
(X).
·
Exits preolivary sulcus.
·
GSE (not SVE – comes from somites not
brachial arches).
·
UMN crossed from contralateral cortex
(UMN causes deviation away)
CN
Nuclei
Nuc.
Ambiguus: motor (9,10,11)
Solitary nuc.:
rostral = taste (7,9,10), caudal = carotid sinus/body (9)
Dorsal motor nuc.
= parasymathetic (10)
Ganglia: Nodose = inferior vagal; Gasserian =
CN5
Wallenbergs (lateral medullary): CN5 (ipsilateral facial analgesia), 8
(vertigo), 9, 10 (hoarse,etc), sympathetics
(ipsilateral Horner’s),
solitary nuc. (taste), cuneate/gracile nuc. (ipsilateral numbness), spinothalamic tract (contralateral
pain/ temp loss – only 1 contralateral); no weakness
Webers: ventral midbrain;
CN3 w/crossed hemiplegia
Claude: dorsal
midbrain; CN3 w/ataxia
Benedikts: CN3 w/
ataxia and hemiplegia
Parinauds: upgaze
palsy, loss of accomodation (fixed pupils) – only 1, large pupils w/ light/
near dissociation, convergence nystagmus, nystagmus retractorius, lid
retraction
Millard-Gubler:
base of pons, CN6 & 7 and contralateral hemiplegia
Medial medullary:
contralat hemiparesis (not face), contralat numbness, ipsi CN12
Lateral pontine (SCA):
ipsi ataxia, contralat pain/temp, deafness, N/V
Locked-in: Bilateral
basilar pons
Bulbar palsy:
LMN CN palsy (usu IX-XII)
Top-of-the-Basilar:
sudden onset AMS, EOM/ pupil/ visual (homonymous hemianopsia) abnormalities,
usu. Embolic.
Brainstem
Reflexes:
Pupil = 2 & 3.
Dolls = 3 & 8 (VestNuc > PPRF >
CN3/6).
Jaw-jerk = 5 only.
Corneal = 5 & 7.
Pupillary = 2 & 3.
Gag = 9 & 10.
Cough = 10 only.
Oculocardiac: V1 to X.
Saccades = frontal
eye fields (area 8) &
parietal eye fields > contralateral PPRF (parietal synapse in
Superior Colliculus 1st > PPRF). Right PPRF = Right gaze.
Smooth Pursuit
= eye > LGB > area 17 > temprorooccipital eye fields (>< FEFs)
> dorsolateral pontine nucleus (DLPN) > vermis/flocculus > med
vestibular nuc > NPH/CN nuclei;
Lateral Gaze:
PPRF, CNVI nuclei (post limb IC);
Vertical Gaze:
FEFs > ant limb IC > synapse in riMLF & interstitial nuc of Cajal 1st
> PPRF.
Lesion of one CN6 nuc.
impairs both
eyes from moving to that side
FEFs go to
riMLF/PPRF, not to CN nuclei directly.
Stimulation: rostral
PPRF = vertical; caudal PPRF = ipsilateral horizontal;
Lesion: cortex/
putamen = toward; thalamic = persistent down gaze; pons/ cerebellar = away,
pontine = pinpoint; midbrain = towards
Pons/cerebellum
(ie contralateral paramedian br. of basilar, contralateral SCA) eyes deviate
away; FEFs (contralateral MCA) eyes devate towards
Opticokinetic reflex:
keeps eyes straight when head is moving (eg. on a train). Direct opticokinetic
path: Retina > nuc of optic tract & Nuc of accessory optic system >
cerebellum/vestibular nuc. Indirect path: Same as pursuit path
(temporalocciptal cortex); lesion gives defect with target moving towards same
side
Nucleus prepositus hypoglossi:
provides info to CN6 nucleus about current head/eye position.
Cerebral
peduncle: lat>med: POTpontine >
corticospinal/bulbar (UE>LE>CN) > frontopontine
![]()
Cerebellum
·
Stimulation
elicits nothing.
Lobes:
·
Flocculonodular
= vestibular (nystagmus, imbalance).
·
Anterior
= spinocerebellar, tone (sl. hyperreflexia).
·
Posterior
= pontine, coordination.
Zones:
·
Vermis:
truncal ataxia, scanning speech
·
Intermediate:
appendicular ataxia, hypotonia
·
Lateral:
tremor, decomposition, dyscoordination, delay of
initiation. Note no hypertonia. Hypotonia from vermis or intermediate zones.
·
Gait
ataxia may be due to cerebellar or posterior column disease (Romberg only + in
latter)
·
Vermis
& IZ have somatotopic organization, not lateral zone.
Layers:
·
Molecular:
basket, stellate cells.
·
Purkinje:
Purkinje cells
·
Granular:
granule, Golgi II cells.
Cells: Granule use glutamate, all others use
GABA.
·
Parallel fibers to Purkinje dendrites
(spiny).
Climbing fibers:
from inferior olive, crossed, to Purkinje dendrites (smooth)
Mossy fibers:
all others. End in glomerulus (Both: glutamate)
Glomerulus: (granular
layer) Mossy fibers & Golgi axons > Granule dendrites
Peduncles:
·
Inferior:
o
Restiform:
All afferent.dorsal spinocerebellar, cuneocerebellar, olivocerebellar
(contralateral, largest # of fibers).
o
Juxtarestiform:
Afferent: vestibulocerebellar (> flocculonodular lobe). Efferent:
Cerebellovestibular.
·
Middle:
All afferent. Pontocerebellar (crossed)
·
Superior:
Afferent: ventral spinocerebellar, Efferent = Cerebellothalamic.
Cerebellothalamic
tract:
·
Dentate > decussates at inferior
colliculus > contralateral VL (VA?/VPL) > motor
cortex.
·
VL: head medial, feet lateral,
extremeties ventral, back dorsal.
·
Only
interposed synapse in caudal red nucleus.
·
Some
fibers descend to contralateral reticular nuclei and inferior olive then
decussate back to ipsilateral cerebellar cortex.
Spinocerebellar
tracts:
·
Dorsal
= LE, ICP, from dorsal nucleus of clarke (C8-L2);
·
Ventral
= LE, contralateral, SCP, L1-S2 cell bodies;
·
Cuneocerebellar =
UE, analogous to dorsal SCT. All go to anterior lobe.
·
Note: propioception from LE in dorsal
spinocerebellar, UE in posterior column
Ganglia:
medial to lateral:
·
Interposed:
(emboliform & globose) to red nucleus to thalamus to motor cortex
·
Dentate:
to VL (VA/VPL) thalamus to motor cortex
Inferior
Olive: inputs from red nucleus, cortex, and spinal
cord to contralateral ICP to cerebellum (ant & post lobes) via
olivocerebellar tract
Red
nucleus: inputs: 1) interposed nucleus of cerebellum
to VL thalamus, 2) cortex. Output: rubrospinal tract, inferior olive (>
contralateral cerebellum). Stimulation elicits contralateral flexion
Feedback
circuits:
1.
Frontal
lobe > Pontine nuclei > Cerebellar cortex > Dentate nucleus > VL
thalamus > Motor cortex (Area4)
2.
Red nucleus > Inferior olive >
Cerebellar cortex (ant & post) > Interposed nuclei > Red nucleus
3.
Spinocerebellar tracts > Anterior
lobe cerebellum > Fastigial Nucleus > Reticular formation/Vestibular
Nuclei > Vestibulospinal & Reticulospinal tracts
![]()
Diencephalon
Diencephalon:
thalamus, hypothalamus, subthalamus, epithalamus (pineal, habenulum, stria
medullaris) (metathalamus = geniculate bodies)
Habenulum:
Input/Output: septal area/ hypothalamus (via stria
medullaris); fasiculus retroflexus (>< VTA >< raphe nuc)
Stria
medullaris thalami: anterior thalamus, preoptic, septal
areas to habenular nucleus
Pineal
·
Composed of glia (5%) &
pinealocytes.
·
Secretes serotonin (>melatonin).
Antigonadotropic.
·
Overactivity delays puberty,
hypofunction causes precocious puberty.
·
Innervated by sympathetic n. – release
NE to stimulate melatonin.
·
Has corpa arenacea or brain sand
(calcifications).
Hypothalamus
·
Anterior/medial = parasympathetic;
Posterior/lateral = sympathetic
·
Ant/post = temperature, lat/med =
feeding
·
Nuclei:
Preoptic:
GnRH (sexually dimorphic)
Suprachiasmatic: circadian
rhythym
Supraoptic:
ADH, uniform large cells (no distinct groups). Projects to
pituitary only.
Paraventricular:
oxytocin, distinct cell groups (magnocellular (oxytocin) & parvocellular).
Projects to brain stem/spinal cord. Also TRH, CRH.
Arcuate:
GHRH, dopamine.
Anterior:
parasympathetic, heat loss
Ventromedial:
staiety center
Dorsal:
stimulation > feeding, savage behavior
Lateral:
feeding center
Posterior:
sympathetic, heat conservation, wakefulness
Median eminence:
where axons from arcuate etc. release releasing hormones into venous plexus
·
Pituitary axis:
o
Supraoptic & paraventricular
nuclei contain magnocelluar neurons > synapse directly on posterior lobe of
pitutary. (Both have input from subfornicial organ)
o
Arcuate etc. contain parvocellular
neurons, synapse on venous plexus in median eminence > anterior pituitary.
·
Feeding:
Neuropeptide Y
feeding thru paraventricular nucleus. Neuropeptide Y containing neurons in the
arcutae nuc. Inhibited by leptin from fat cells. VMH & LH centers
oversimplified.
·
Input: MFB, fornix (hippocampus), stria
terminalis (amygdala), DLF (midbrain central grey), retinohypothalamic, nucleus
solitarius. Generally from limbic system/ amygdala/ hippocampus – not neoortex.
·
Output:
MFB, stria terminalis, Dorsal Longitudinal Fasiculus (parallels MFB thru medial
hypothalamus), mamillothalamic, mammillotegmental, hypophyseal, descending
autonomic
Tuberoinfundibular
tract: hormones from arcuate nucleus (tuberal
region) released in capillary plexus in median eminence to portal veins to
capillaries in anterior pituitary
Supraopticohypophyseal
tract: Magnocellular neurons from supraoptic & paraventricular
nuclei (histologically identical, both nuclei in supraoptic region) to
posterior pituitary
Pituitary
·
Anterior lobe from ectoderm (Rathkes
pouch), Posterior from neurectoderm (diencephalon)
·
Vascular supply:
Anterior:
·
Pars
distalis: hormone secretion. Basophils, acidophils,
chormophobes.
·
Pars
intermedia: basophils, chromophobes, & colloid
cysts (remnants of Rathke’s pouch). Produces MSH (melanotropin), stimulates
melanocytes to produce melanin
·
Pars
tuberalis: around stalk. Squamous cells, follicles of
suboidal cells, hypophyseal plexus veins
Posterior:
·
Pars
nervosa & infundibulum.
·
Has pituicytes (resemble astrocytes).
Has Herrings bodies (storage of ADH & oxytocin) & glomeruli
Sensory:
·
VPL (body), VPM (face)(both to 3/2/1), VPI (vestibular), LGB (to
17), MGB (from inf coll. To 41/42, tonotopic)
Non-specific:
to parietotemporal association areas:
·
Pulvinar: Auditory/vision relay. Projects to
sensory association corticies: occipital (18/19), parietal, & temporal (not
frontal).
·
LP: Output to
5/7 (SIII)
Motor:
·
VL (VLo: from
GP to area 6/8, VLc from cerebellar/red nuclei to area4);
·
VA (from GP,
to area6 & nonspecifically to cortex (esp prefrontal) for recruiting),
·
Centromedian:
(from GP/area4, to putamen. Stimulation at 6-12 Hz produces activity
(recruiting) of large areas of cortex)
·
All 3 receive input from GP via
thalamic fasiculus.
Limbic/Behavioral:
·
Anterior /LD:
from MB (mammillo-thalamic tract) and hippocampus (fornix), to cingulate.
·
DM: to/from
prefrontal lobe (also input from limbic structures), affected in Korsakoffs,
controls affective behavior/memory, smell (from olfactory areas)
Intralaminar:
·
CM: To putamen
(see above).
·
Parafasicular nuc.:
To caudate. Both receive ARAS/spinothalamic input & have diffuse cortical
projections for arousal.
·
Rostral intralaminar nuclei:
thalamic pacemaker.
·
Thalamic reticular nucleus:
thin sheet on lateral wall. No cortical projections, projects to other thalamic
nuclei & reticular formation. Receives all affarents & efferents w/
collaterals. Mostly GABAeric?
·
Extremities ventral, back dorsal; head
medial, caudal lateral
·
Caudate
·
Putamen
·
Globus Pallidus interna (GPi) and externa
(GPe)
·
Striatum: Caudate and Putamen
·
GP = diencephalon, Put/Caud (&
GPe?)= telencephalon.
·
Subthalamic Nucleus (STN)
·
Substantia Nigra
·
Damage: GP = athetosis, STN =
hemiballismus, Striatum = chorea, SN = rigidity, tremor
Control intensity & timing of movement
1.
Direct
2.
Indirect
3.
Nigrostriatal loop: Facilitates direct
loop by D1 receptors & inhibits indirect loop by D2 receptors. Cortex (glu)
> Striatum (GABA) > SNpr > SNpc (dop) > Striatum > GP > Thalamus
> Cortex.
·
D1 receptors on striatonigral neurons,
D2 receptors on striatopallidal neurons.
o
Dopamine does not directly
excite/inhibit striatal neurons, but changes K conduction to raise/lower RMP.
Output
Striatum:
1.
to GP: GABA & to GPe = enkephalin
(spiny type I), to GPi = substance P (spiny type II) (Aspiny neurons are
intrinsic Putamen only)
2.
to SNpr (GABA)
GPe: to STN
GPi:
1. Thalamus: Ansa lenticularis +
Lenticular fasiculus (Forel’s field H2) >
Thalamic Fasiculus (Forel’s field H1) > VA/VL/CM (Thalamic fasiculus
also contains fibers from cerebellar dentate nucleus)
2. Pallidotegmental: to VTA
·
Thalamostriate fibers: from CM/
parafasicular nuc. to striatum
Subthalamus:
Subthalamic nuclei + Zona incerta (grey matter b/t thalamic & lenticular
fasiculi). Use glutamate
Substantia
Nigra: Neurons contain melanin granules. Fibers to
putamen, caudate, sup colliculus, thalamus (not
GP). Pars Reticulata: input. Pars compacta:
output, dopamine (to spiny neurons in putamen).
·
Function:
integrating short-term memory, assigns salience to stimuli for emotion
(modulates limbic system/ hypothalamus) & memory. No olfaction.
·
=
Subiculum, hippocampus, dentate gyrus All archicortex - 3 layers.
(Parahippocampal gyrus has 5 layers).
·
Hippocampus proper = Ammon’s horn
(Ammon = egyptian god with rams’ head)
·
C-shaped:
Parahippocampal gyrus (outside) > Subiculum (transition) > hippocampus
(CA1>2>3) > Dentate gyrus (hilus = CA4) (curves back over subiculum).
·
CA1=parvocellular
(vulnerable to anoxia. = Sommer’s sector). CA3=magnocellular
Alveus:
white matter b/t
hippocampus & temporal horn composed of efferent fibers; most medial
portion is Fimbria (> fornix)
Cellular
Layers of Hippocampus (in to out):
Polymorphic layer
(axons,output) > pyramidal cell layer(soma) > molecular layer (input,
dendrites). Dentate gyrus: pyramidal cell layer replaced by granule cell layer.
Input:
1. Entorhinal cortex, Via
A.
Perforant pathway >dentate (mossy fiber) >CA3 (Schaffer’s collaterals)
> CA1 >subiculum) or
B.
Alvear pathway (straight to hippocampus),
2. Fornix (septal nuclei, substantia
innominata etc)
3. Cingulate cortex
Output:
Fornix:
Subiculum / pyramidal cells of hippocampus > alveus > fimbria >
fornix.
Subiculum
> postcommisural (
Hippocampus > precomissural (septal
area > lateral hypothalamus).
Also
direct output to entorhinal cortex & amygdala (small).
Hippocampal
commisure: between
fornices
Schaffer’s
collaterals: branches
of pyramidal axons which synapse on other hippocampal cells (i.e. CA3 to CA1)
Dentate: efferent fibers only to hippocampus
(mossy fibers).
Indusium
griseum: remnants of
hippocampus over corpus callosum.
Fornix
·
Main efferent from hippocampus.
·
Body (rostral to thalamus) >
Columns (posterior to anterior commissure).
·
Forniceal commissure:
aka psalterium. Is rostral to anterior commissure.
Papez
circuit
·
Probably serves short-term memory (MB,
Ant. Thalamus) more than emotion.
·
Bidirectional: Subiculum > fornix
> MB > MT tract > Ant. Thalamus > Cingulum > entorhinal cortex
> subiculum
Function: Interface
between cortex and hypothalamus/brain stem for emotional response &
emotional memory.
Stimulation:
Fear & Rage
Corticomedial group:
olfaction, > hypothalamus/pituitary (high concentration of
enkephalins, somatostatin, and dopamine)
Central nucleus: input/output to hypothalamus &
autonomic brainstem
Basolateral group = cortical, sensory input (temporal),
uses glutamate
Input: Olfactory (lateral olfactory stria),
taste (Nucleus solitarius), and auditory (temporal cortex). Sensory,
prefrontal & cingulate cortex.
Output:
1. Stria terminalis (CM >
hypothalamus, septal area),
2. Ventral amygdalofugal tract (BL >
hypothalamus, PAG)
3. Diagonal Band of Broca (septal area)
4. Direct: Cortical/ hippocampus/ DM
thalamus/ striatum/ brainstem.
Only meager
projections back from hippocampus, thalamus & hypothalamus.
Kluver-Bucy: Bilateral damage. Docility,
Hyperorality, hypersexulaity, visual agnosia (psychic blindness),
hyperphagia, exploring
Limbic system
Amygdala, septal area, hypothalamus,
anterior thalamus, anterior cingulate & orbitofrontal cortex, ± hippocampus.
Controls
emotion (self & species preservation, learning, emotional processing/
social behavior).
Output of
limbic system to brainstem: DLF (hypothalamus), fasiculus retroflexus
(habenulum), Mamillotegmental fasiculus, MFB (amygdala/ septal area/
hypothalamus).
General
path: hypothalamus (endocrine) > Midbrain PAG > Autonomic & Motor CN
nuclei
All tracts are
bidirectional.
Limbic
system has analogous loops to basal ganglia:
1. Direct path: Limbic/Prefrontal cortex
& intralaminar nuclei > NAcc (ventral striatum) > ventral pallidum
> DM/Ant thalamus > cortex. responsiveness
(memory/ emotion /learning) to stimuli.
2. Indirect Path: same as above but VP
> STN > VP. Inhibitory
3. Mesolimbic: Nacc > VTA > Nacc.
Excitatory. Analogous to SNpc. (both use dopamine).
LAMP = membrane
glycoprotein marker for limbic system neurons
Septal
area:
Subcallosal and paraterminal gyrus
& septal nuclei (NucAcc, Meynert). Relay for
hippocampal afferents to hypothalamus.
Input from fornix (hippocampus), brainstem,
hypothalamus (MFB), anygdala (diagonal band of Broca), medial
olfactory stria.
Output: MFB to hypothalamus, stria medullaris to
habenulum, diagonal band of Broca to amygdala, also hippocampus (fornix),
cortex, thalamus, MB. (not basal ganglia)
Medial
Forebrain Bundle: septal area to hypothalamus to
brainstem (reticular formation & autonomic areas). Bidirectional.
Mesocorticolimbic
system
Midbrain Ventral
Tegmental Area (VTA, aka interpeduncular nucleus) to limbic system (NAcc, amygdala, hypothalamus, cortex);
Uses Dopamine; Acts similar to SN in BG
system.
excitation of Nacc to stimulation of DM thalamus & limbic
cortex to
responsiveness to stimuli. Role in positive reinforcement/Addiction
Nucleus
accumbens: where putamen & caudate meet
anteriorly; functions w/septal nuclei. Recives VTA input. Role
in addiction/ gratification.
Raphe nucleus in low pons/medulla is inhibitory
(serotonin)
Raphe nuclei & locus ceruleus also send
descending fibers to spinal cord. To affect pain transmission (see analgesia)
Nucleus reticularis pontis oralis functions
in wakefulness & REM sleep. Excited by hisaminergic neurons in posterior
hypothalamus; inhibited by GABAergic neurons in anterior hypothalamus.
Parvocellular Area: BP manitenance,
respiration?
![]()
·
Homotypic cortex:
has typical layers (association areas). Idiotypic/
heterotypic cortex has altered layers (primary motor/sensory areas)
·
Has columnar organiztion of 100-300
neurons w/same function.
·
Parallel networks for language,
attention, learning/memory, face/object recognition, & comportment.
·
2 heteromodal association areas:
temporoparietal (sensory integration), and prefrontal (integrates motivation
with stimuli – punishment/reward).
Allocortex
·
3
layers.
·
Pyriform
cortex (paleopallium, 3-5 layers), hippocampus and dentate gyrus (archipallium,
3 layers).
·
Note
entorhinal cortex = parahippocampus, pyriform cortex = uncus.
Mesocortex
·
3-6
layers.
·
Paralimbic
areas: cingulate/ subcallosal/ paraterminal gyri, parahippocampal gyrus,
temporal pole, insula, & caudal orbitofrontal cortex.
Band of Baillerger: in layer 4b. In area 17 is Stripe of
Gennari (not in 18/19 – extrastriate cortex).
Temporal
lobe
Superior gyrus = language, middle &
inferior = visual discrimination.
Vascular supply: Medial
= PCA, superior/lateral = MCA.
Deficits:
Bilat middle & inf = psychic blindness, Bilat
heschls = deafness, unilat = slight contra loss; vestibular cortex (post to
Heschl) = decreased OKN; time perception (either side); dom = auditory leaning,
nondom = visual learning
Parietal
lobe: Dominant = math/language, Nondominant =
spatial perception;
Parietal lesions:
Dominant:
Gerstmanns (finger agnosia, right-left confusion, acalculia, agraphia), also
alexia, anomia, tactile agnosia, ideational & contsructional apraxia;
Non-Dominant:
anosognosia (= neglect, denial of illness), dressing apraxia, topographic
memory loss, constructional apraxia, asomatognosia (hemineglect)
Angular
Gyrus: visual processing of words; damage causes
alexia and agraphia - inability
to read/ write with intact speech comprehension, Gerstmann’s
Occipital
lobe:
Lesions:
Bilateral: cortical
blindness; Anton’s syndrome (aka Anton-Babinski, denial of blindness);
Dominant:
simultagnosia (identify parts of picture, not whole thing); prosoprognosia.
Right occiptotemporal:
color agnosia, left = color anomia;
Balint syndrome:
psychic gaze paralysis/peripheral inattention (bilateral posterior
parietooccipital)
Primary
motor (Area 4)
·
Lesion = hypotonia, paresis (no
fine movement); BG lesion = hypertonia.
·
Neurons innervate synergistic sets of
muscles (not individual mm.)
·
Cortical columns represent movements,
not individual muscles. Chiefly functions in distal mm.
·
Hand area: middle bend of central sulcus
Premotor
area (6)
·
Planning/ timing.
·
Lesion produces apraxia of
complex, learned movements, unable to produced delayed response; has homonculus
SMA
(medial area 6)
·
LE anterior, face posterior.
·
Functions in coordinating bilateral
movements.
·
Stimulation – gross bilateral
movement w/urge to move (premotor – discreete movement, requires higher stim,
no perception of urge to move).
·
Movement on either side
activates.
·
Lesion –spasticity (vs area 4)
and involuntary grasping, akinesia, poverty of speech (all resolve in 6 weeks).
Unilateral lesions usually cause no permanent deficits.
·
Both SMA & premotor send fibers
directly to spinal cord, have homunculi, and higher threshold than MI.
Frontal
Eye Fields (area
8)
·
Area 8 >
·
Fibers don’t go to CN nuclei directly.
·
For voluntary saccades.
·
Stimulation: bilateral deviation away
·
Lesion: cant target objects on command
(eyes tonically to same side).
Occipital Eye Fields
·
aka posterior parietal, temporooccipital
(widely dispersed).
·
Subserve
involuntary smooth pursuit.
·
Stimulation:
eye deviation away (like FEFs but higher threshold, longer latency).
·
Lesion:
eye deviation to same side (like FEFs) but can target w/ saccades and have
problems following objects
Sensory Cortex
·
3a
= muscle spindles, 3b = skin (slow & rapid), 1=rapidly adapt skin, 2 =
pressure/joint. Input: 3b > 2 > 1.
·
Damage
causes topagnosia (decreased localization), astereognosis (no pain/temp loss).
·
Each
has separate homunculus.
·
Vestibular
& gustatory cortex lie in operculum.
SII:
·
On superior bank of lateral sulcus.
Homunculus is inverted.
·
Stimulation elicits bilateral sensations.
·
Role in identifying objects by touch
& storing memories (old view – pain perception)
Somatosensory
association (areas 5&7)
Agnosias
·
Can’t identify objects.
·
Visual = bilateral occipitotemporal
(ex Prosoprognosia - faces).
·
Tactile = area 40 (supramarginal).
·
Auditory = area 22.
Apraxia
·
Ideational = dominant parietal,
failure to carry out sequences of acts, although can do parts. Have pt act as
combing hair w/out comb.
·
Ideomotor = Dominant Parietal
(supramarginal gyrus/ arcuate fasiculus). Can perform acts spontaneously but
not on command. Can conceive movement but not perform until cued; test by using
utensils, dressing, etc.
·
Note actions conceived in dominant
parietal cortex, travels arcuate fasiculus to L frontal & corpus callosum
to R frontal for performance.
Aphasia
·
Wernicke’s: Receptive. Fluent but unable to comprehend. Paraphasias,
“word salad”
·
Broca’s: Expressive. Able to comprehend but non-fluent.
·
Conduction: impaired repetition (like Wernickes
(fluent paraphasic) but with retained comprehension & awareness of
deficit),
·
Transcortical motor/sensory: normal
repetition, echolalia (sensory = temporoparietaloccipital jxn, motor = frontal
lobe).
·
Brocas & Wernickes both have
impaired repetition.
·
Pure word deafness (can still read,
echolalia) = area 22, anterior (bilateral > left).
·
Subcortical (Left BG) lesions may also
cause aphasia.
·
Exner’s area:
superior to Brocas. Causes agraphia without aphasia.
Alexia
without agraphia
·
Left occipital lobe (geniculocalcarine
tract and corpus callosum). Usually has hemianopsia & color anomia.
·
With agraphia
= left angular gyrus (Gerstmans).
·
Without hemianopsia
= rare, deep white matter, corpus callosum (not geniculocalcarine)
Color
anomia: left mesial occipitotemporal lobe
Achromatopsia:
right inferior occipitotemporal (color blindness)
Prefrontal
cortex
·
Orbitofrontal:
social appropriateness (lesion – disinhibition), connects w/limbic system
·
Dorsolateral:
motivation (lesion – apathy), connects to motor areas.
Fasiculi
·
Uncinate:
antertior temporal to orbitofrontal
·
Arcuate:
Superior & Middle frontal gyri to temporal (Wernicke to Broca)
·
Cingulate:
medial frontal & parietal to parahippocampal.
Corpus
callosum
·
Does not have projections between
areas 1,2,3 (S1),4 (M1), or 17 (V1).
·
Section:
splenium = unable to read left field; ant. 1/3 = nothing; all = left hand
apraxia
·
Tapetum:
white matter lateral to temporal horn/ atrium (medial to optic radiations)
·
Calcar avis:
medial to temporal horn/ atrium
Gyri
·
Precuneus:
medal b/t paracentral lobule (S1) and cuneus (separated by parietooccipital
sulcus);
·
Lingual:
posterior to parahippocampal gyrus (medial to collateral sulcus);
·
Occipitotemporal:
inferior, lateral to collateral sulcus.
·
Inferior frontal:
lateral: pars orbitalis > triangularis > opercularis. Medial: gyrus
rectus > subcallosal area > paraterminal gyrus. (contiguous w/ cingulate)
·
Supramarginal:
end of Sylvian fissure.
·
Angular:
end of superior temoral fissure (more posterior)
o
Both separated from superior parietal
lobule by intraparietal sulcus.
·
Cingulate:
between cingulate sulcus (superior) & sulcus of corpus callosum
Corticobulbar
fibers
·
Project to sensory relay nuclei
(gracilis, cuneatus, trigeminal, solitary nuclei),
reticular formation, & motor CN nuclei.
·
Fibers to gracilus & cuneatus
nuclei leave pyramids & transverse reticular formation or medial lemniscus.
·
Fibers to trigeminal & solitary
nuclei are from frontoparietal cortex.
·
Corticoreticular fibers from premotor,
motor & sensory cortex to medulla (gigantocellular) & pons (oral
pontine).
·
Motor fibers from 1°
motor area; bilateral except CN 7 (lower) & 12. (However lesion to fibers
to 12 is asymptomatic or mild)
·
Pseudobulbar palsy
requires bilateral lesions.
Internal
capsule
·
Anterior
limb: frontopontine, anterior thalamic
radiations.
·
Genu:
corticobulbar, corticoreticular.
·
Posterior
limb: Corticospinal,
Parieto-occipital-temporal-pontine, superior thalamic radiations, corticofugal
fibers
·
Sublenticular = auditory radiations,
Retrolenticular = visual radiations.
Floor
of 4th ventricle
·
Rostral to stria medullares:
median eminence > facial colliculus > sulcus limitans.> inferior
cerebellar peduncle.
·
Caudal (Rhomboid fossa):
hypoglossal trigone > vagal trigone. Area postrema most caudal.
·
Below 4th ventricle:
dorsal median sulcus > gracile tuburcle > dorsal intermediate sulcus >
tuberculum cinereum > dorsolateral sulcus.
·
Ventral: pyramid
> preolivary sulcus/ XII > olive > postolivary sulcus > IX, X, XI.
·
Infundibular recess: ventral to mamillary bodies.
·
Floor of 3rd ventricle:
Ant to post: optic chiasm > infundibulum > tuber cinereum > MBs
Lateral
ventricle:
·
Medial to lateral: fornix/ septal v.
> velum/ choroid > thalamus/thalamostriate/anterior caudate v
·
Transvelum interpositum approach:
between choroid & thalamus (lateral)
Nasal
septum: ethmoid (superior) & vomer (inferior).
Cartilage anterior
Orbit: maxilla (inferior), lacrimal (medial anterior), ethmoid (medial
posterior), frontal (superior), sphenoid (posterior superior), palatine
(posterior inferior), zygomatic (lateral)
Inferior
orbital fissure: occ V2
Anterior
clinoids: Optic canal &
Lillequist’s
membrane: Between CN3 medially, divides
interpeduncular cistern from chiasmatic cistern. Seen b/t ICA
& CN2.
Cavernous
sinus: CN6 only one inside
Tendinous
ring: CN2,
3, 6, nasocillary, & ophthalmic a. inside (Outside: frontal and lacrimal
nn. off V1, CN4, ophthalmic v.)
Dura:
innervation - supratentorial = V, infratentorial = X and C1-3 (no VII)
Falciform
ligament: between anterior clinoids, over optic n.
Annulus of Zinn: In the superior orbital
fissure. The CN 3,6 and nasocilliary nerve pass
through it. Lacrimal, frontal, CN4, and
ophthalmic vein travel lateral to it.
Pterion:
frontal, greater wing of sphenoid, parietal, squamous temporal
Houghtons lines
Petrous
bone: Geniculate ganglion:
posterolateral to ICA, posteromedial to formen spinosum, anterior to superior
semicircular canal, medial to cochlea; lateral to middle ear cavity. GSPN:
runs over & parallel to
Petrous
Cavum:
septum pellucidum, vergae (posterior), velum interpositum (3rd vent)
Cisterns:
Ambient:
SCA, CN4, basal v. Rosenthal. Interpeduncular:
CN3, basilar a. Quadrigeminal: Vein
of Galen. CPA: CN5,7,8,
AICA. Prepontine: Basilar a. Lateral cerebellomedullary: PICA,
choroid plexus of 4th ventricle.
Transverse
Crest: separates superior/inferior nerves.
Bill’s Bar: separates facial n. from superior vestibular n.
Lateral
motor system = corticospinal + rubrospinal
Medial
motor system = vestibulospinal + reticulospinal
Corticospinal
tract:
·
Lateral:
90%. Cross at decussation.
·
Anterior/Ventral:
10%, remain ipsilateral, then cross at level of
termination in SC, posture control.
·
All synapse on interneurons 1st
(2°)
in ventral horn & use glutamate.
·
When damaged rubrospinal takes over.
·
Babinski from corticospinal (or
cortical) damage.
·
Note
no direct connection to CN 3, 4, 6, DMN vagus.
·
From:
Betz cells 3%; Area 4 = 30%, area 6 = 30%; area 1,2,3
= 40%.
·
40%
of fibers are poorly myelinated.
Rubrospinal
tract: (Fibers from cortex 4/6 & cerebellum
>) red nucleus > crosses in ventral tegmental decussation >
cervical/thoracic cord. Flexor tone.
Vestibulospinal
tracts
·
Lateral:
from lateral vestibular nuc, to all levels SC, extensor tone;
·
Medial:
from medial vestibular nuc., to cervical cord only,
CNXI Nuc. (neck mm.), role in vestibular modulation of
head position via neck, runs in MLF.
·
Both remain ipsilateral.
Tectospinal:
From superior colliculus, reflex movements for sight; cross at origin; to
cervical levels only
Reticulospinal
tracts
·
Pontine reticular nuc > medial
reticulospinal tr ipsilateral > extensors.
·
Medullary reticular nuc > lateral
reticulospinal tr bilateral > flexors &
autonomic info.
Lateral
spinothalamic
·
Pain & temperature
·
Body in DRG (1°)
> axons enter Lissauer’s tract > synapse in Lamina II on soma (2°)
> cross @
level of entry in ventral white commissure > (most fibers to reticular
formation = spinoreticular tract)
> VPL/ VPI & intralaminar nuclei (3°) > sensory cortex. (some spinoreticular
fibers remain ipsilateral)
·
Paleospinothalamic tract:
C fibers to layer 2 to reticular formation, intralaminar nuclei, PAG; burning
pain.
·
Neospinothalamic tract: Ad
fibers to layer 1 to VPL, sharp pain
·
Visceral pain:
Ad
& C fibers in sympathetic nerves > lamina 7 > spinothalamic tract
(parasymathetics carry nonpainful sensation)
Anterior
spinothalamic = light touch; cross @ level of entry. To VPL.
Nucleus
dorsalis of Clarke: thoracic to C8, layer 7,
proprioception, forms dorsal spinocerebellar tract
Dorsal
spinocerebellar tract
·
Muscle spindles & Golgi tendon
organs of LE (1°)
> synapse ND of Clarke (lamina 7, T1-L2) @ level of entry (2°)
> DSCT > Inferior Cerebellar Peduncle > ipsilateral anterior lobe cerebellum.
·
Uncrossed. Detects Individual muscles.
·
At levels L3-S5 ascend in fasciculus
gracilis to L1/2 then synapse in NDC (2°).
·
Ventral:
LE, synapses ventral horn (2°)
> crosses @ level of entry > VSCT > crosses in pons to contralateral
·
Cuneocerebellar (& Rostral – cats
only): UE, analogous to dorsal & ventral; enter
@ C1-8 > ascend in fasiculus cuneatus > synapse in accessory cuneate
nucleus in medulla (2°)
> ant lobe cerebellum.
Dorsal
Colums/Medial Lemniscus:
·
Touch/Pressure.
·
DRG (1°) > Gracilus (LE) / Cuneate (UE) Fasiculus
> Gacilus/ Cuneate Nuc. (2°)
> decussation > medial lemniscus > VPL thalamus (3°)
> area 3/2/1 & SII ( > motor cortex for feedback)
·
Note transmits proprioception only
from UE, not LE.
·
Lateral cervical system:
(aka spinocervical thalamic tract). Light touch. Enter C8-L4 > synapse in
lamina 4 > ascend in SCTT > synapse in lateral cervical nucleus (C1-4)
> medial lemiscus > VPL > area 3/2/1
Rexed’s
lamina
·
Lamina I: fast pain.
·
Lamina II: Substantiosa gelatinosa.
Slow pain, ascend/descend several segments in Lissauer’s tract (outside lamina I).
o
Both have substance P & glutamate receptors for 1°
nociceptive afferents.
·
Layer 3& 4: nucleus proprius
(touch/pressure/proprioception);
·
Layer 7: zona intermedia (dorsal
nucleus of
·
Layer 9: motor neurons.
Dorsal roots
·
Ganglionic
neurons use glutamate, substance P, somatostatin, CCK.
·
Roots
divide into medial (from encapsulated sensory organs, Golgi,muscle
spindles, thick myelin) and lateral (from free nerve endings, thin myelin,
pain/temp) bundles. In the spinal cord these divide into ascending &
descending branches.
Ventral horn SC: flexors = dorsal, extensors = ventral
(same as tracts); trunk = medial, hand = lateral
Somatotopic organization: Cortex, BG, Red nucleus, reticular
formation, Vermis & intermediate zone of cerebellum
Anaglesia
PAG (midbrain) & PVG (hypothalamus) (both
enkephalin) to nucleus raphe magnus in medulla (serotonin, NE) to dorsal horn of spinal cord (enkephalin) to
inhibit nociceptive 1°
sensory neuron axons and projection neurons’ dendrites. PAG stimulation elicits
fear, diplopia, etc. PVG better tolerated.
Brainstem
sections:
Medulla: Inferior
Olive, accessory cuneate, dorsal nucleus X, nucleus ambiguus, solitary nucleus
Pons:
![]()
Brachial
Plexus: Roots (C5-T1)
> Trunks (Upper/ middle/ lower) > Divisions (ant/ Post) > Cords
(Lateral/ Medial/ Posterior)
Arise from roots before plexus:
Dorsal
scapular: C5. rhomboids, levator scapulae (stabilize scapula).
Long thoracic:
C5,6,7. serratus anterior
(abduct scapula > winged scapula, cut during axillary node dissection).
Arise
from upper trunk:
Suprascapular:
supra (abduction) & infraspinatus (ext rot)
Arise
from cords:
Lateral & medial pectoral:
pectoralis major; (lateral & medial cords)
Musculocutaneous:
(lateral) brachialis, coracobrachialis, biceps (elbow flexion)
Median: (lateral &
medial cords). Travels w/ brachial a. in arm. Goes thru 2 heads of pronator teres in forearm. Gives off anterior interosseous n. (FPL, index
FDP, pronator quadratus). Palmar cutaneous
branch: arises 5cm proximal to wrist. Recurrent motor br. To thenar
muscles arises distal end carpal tunnel.
Muscles: Hand = LOAF: Lumbricals 1&2,
opponens, APB, FPB (superficial); all other flexors/ pronators in forearm,
palmaris longus.
Autonomous zone = tip of index finger.
Ulnar: (medial cord). Runs behind medial epicondyle, thru Guyons canal. Dorsal cutaneous branch (sensation to
dorsum of digits 4 & 5) leaves in forearm.
Muscles: Adductor pollicis, FPB (deep), hand
intrinsics; FCU, FDP3/4
Autonomous zone = tip of little finger
Subscapular:
(posterior) teres major (adducts humerus), subscapularis (med rot humerus)
Thoracodoral:
(posterior) lattisimus dorsi (adducts shoulder)
Radial: (posterior). Around spiral groove of humerus. Divides below elbow into posterior interosseous (thru arcade of
Frohse, all muscles in forearm & hand) and superficial branch (sensory)
Muscles:
triceps, brachioradialis (musculocutaneous = brachialis), extensors/ supinator,
APL (injury from crutches). If cut in forearm no motor loss, only sensory.
Autonomous zone = 1st web space
dorsum
Axillary:
(posterior) deltoid, teres minor (injured with anterior shoulder
dislocation)
Thumb:
·
Median = LOAF: FPL, Abductor pollicis
brevis (perpendicular to palm), opponens,FPB (superfical)
·
Ulnar = adductor policis, FPB (deep);
·
Radial = abductor pollicis longus
(parallel to palm).
·
Ad/Abduction is perpendicular to palm,
flex/extension is in plane of palm.
Interosseous
muscles: palmar =
adduct fingers; dorsal = abducts 1&4, flexes
Lumbricals:
extends IP joints, flexes MCP joints
Carpal
tunnel: contains FPL, FCR, Median N., FDS, FDP
Superior gluteal:
gluteus medius, min. (thru greater sciatic foramen, above pyriformis m.; inf.
Gluteal & sciatic below pyriformis)
Inferior gluteal:
gluteus maximus
Femoral: iliopsoas,
quads
Obturator: adductors,
gracilis
Sciatic: hamstrings
(biceps), part of adductor magnus, semitendinous, semimenbranous. To:
Tibial:
gastroc, TP, FHL (all foot mm.)
Common
peroneal: to
Superficial
peronal: peroneus longus & brevis
Deep
Peroneal: Tib ant, extensors
Biceps fermoris only has innervation from
peroneal component of sciatic n. > differentiate sciatic from peroneal n.
injuries
Ilioinguinal n.:
at risk in appendectomies (McBurneys incision)
Ulnar n. vs C8 root injury:
ulnar n. splits 4th digit, C8 covers entire finger. C8:
EMG ¯
ECU (radial), APB (median), paraspinous mm, NCV normal. Plexus (Lower trunk/ medial cord): normal paraspinal, abnormal
sensory median antebrachial cutaneous n.
Radial n. vs C7 root: C7: FCR
(median). Posterior cord: deltoid.
Peroneal n. vs L4/5:
L4/5: loss of foot invertors
Femoral n. vs L3:
L3: loss adductors/ quads
![]()
C1:
has no dorsal ramus
Odontoid:
2 primary ossification centers at base, 1 secondary at apex.
Canal
diameter: Cervical =18mm, stenosis = 12mm; Lumbar =
20-22mm, stenosis <15mm
Cervical
ligaments: posterior longitudinal ligament becomes
tectorial membrane
Facets:
Cervical: inferior facet is medial. Thoracic: coronally oriented. Lumbar:
superior facet is medial.
Neck:
·
Recurrent laryngeal n.:
left around aorta, right around subclavian a.; both off vagus, posterior to
inferior thyroid a.
·
Superior laryngeal n.:
travels w/superior thyroid a. in 15%.
·
Phrenic n.:
anterior to anterior scalene, behind IJ.
·
Subclavian a. & v.
run between anterior & middle scalene.
·
Stellate Ganglion:
inferior cervical + upper thoracic ganglia
Bladder:
·
Parasympathetics:
pelvic n. (S2,3,4) to detrusor mm.
·
Voluntary:
Pudendal (S2,3,4) to external sphincter.
·
Sympathetics:
inferior splanchnic n. to inferior mesenteric ganglion to inferior hypogastric nn. to
internal sphincter (a),
& bladder wall relaxation by inhibiting parasympathetics in pelvic
ganglion. (T10,11,12).
·
UMN = spastic, propantheline or
oxybutnin (Ditropan), imipramine (TCA, anticholinergic); LMN = atonic,
bethanecol, methacholine.
Melanocytes
located in cervicomedullary pia. Made by tyrosinase.
·
PICA can
arise from vertebral artery (VA) extradurally, can be
injured during dissection of C1.
·
VA
is 3mm from lateral uncovertebral joint, may run through vertebral bodies.
·
VA
enters transverse foramen above C6 or at C7 in 13%.
·
The
left VA is dominant in 36% of patients, hypoplastic in 6%, and absent in 2%.
The right is dominant in 23% of patients, hypoplastic in 9%, and absent in 3%.
Equivalent right and left VA present in 40% of patients.
·
2%
of VA do not enter BA or are otherwise anomalous at C1
·
Artery
of Adamkiewicz: Enters
spinal canal at T9-12 on the left to supply T8 to conus.
Vascular
Supply
Internal
capsule: Ant limb = Heubner; Genu =
Striatum:
Lenticulostriate a, Heubner, Ant choroidal
Thalamus:
PCA: ant & post choroidals, thalamoperforators (basilar, PCOM, P1),
thalamogeniculate (MCA doesn’t supply)
Substantia
Nigra: PCA/Pcom
Cortex:
·
ACA = hemiparesis (LE), mild sensory;
·
Achor = hemiplegia, hemianesthesia,
homonymous hemianopia.
·
PCA = cortical blindness, Balints,
prosopagnosia
Ventricles:
lateral = anterior and lateral posterior choroidals, 3rd = medial
posterior
Superior
Saggital Sinus drains to right transverse sinus
Aortic
arch:
·
R Innominate (> R CCA > R VA
> R thyrocervical trunk > subclavian) > L CCA > L subclavian (>
VA).
·
·
Rarely can have nonbifurcating CCA w/
ECA branches.
Aberrant
Persistent stapedial a.:
intratympanic, from petrous
Intracranial
Petrous: > vidian
a. > caroticotympanic a > middle ear
Cavernous:
meningohypophyseal a. C4/5 (tentorial of Bernasconi & Cassanari, inf.
Hypophyseal, dorsal meningeal), inferolateral trunk C4, McConnel’s capsular.
Supraclinoid:
Sup. Hypophyseal.
Intradural: ophthalmic
> pcom > ant choroidal.
Hypophyseal
a.: Inferior = post pituitary, superior = anterior
pituitary
Ophthalmic
a.: 0.5% arise from
middle meningeal. May also arise from cavernous genu (C3)
Fetal
P-comm: unilateral in 20%, bilateral in 8%
Anterior
Choroidal
·
Cisternal segment > Plexal point
(enters choroidal fissure) > Plexal segment.
·
Arises off of MCA or Pcom in 25% of
patients
·
Supplies: optic tract, post limb IC, BG, substantia nigra?, thalamus, amygdala, hippocampus (mostly from PCA), tail
of caudate (not hypothalamus).
·
Had been sacrificed as treatment for
Parkinsons.
·
Anterior temporal lobe masses displace
it medially.
·
Injury:
Hemiplegia, hemihypesthesia, homonymous hemianopsia (cognition unimpaired)
·
ACOM: perfs to chiasm
·
Heubner: (medial striate a.) arises from A2 (86%) >
A1. Supplys anterior limb IC, BG. Damage causes hemiparesis (arm & face),
aphasia (on left).

MCA
·
M1 (to bifurcation)> M2 (insula, to
circular sulcus of insula) > M3 (circular sulcus to edge of insula) > M4
(cortical, opercular)
·
Sylvian point:most
posterior branch of MCA leaving sylvian fissure
·
(Lateral) Lenticulostriate a.: from M1. BG,
IC.
·
Anterior temporal a. from M1.
PCA
·
P1 (to PCOM)> P2 (in ambient
cistern) >P3 (in quadrigeminal cistern) > parietooccipital, calcarine
·
Thalamoperforators:
from basilar tip, pcom, P1
·
Medial post choroidals:
from P1; midbrain tectum, thalamus, 3rd ventricle
·
Lateral post choroidal:
from P2; thalamus, lateral ventricle choroids
·
Med & Lat thalamogeniculate a. :
from P2, post thalamus, crus cerebri
·
P3: Post
temporal a. (anast. W/MCA); Internal occipital> Parietooccipital (to MCA),
Calcarine (to ACA)
Vertebral
a: Left dominant in 50%, right 25%, neither 25%. 40% one hypoplastic.
1-25% terminates in PICA. Both off subclavian a.
PICA:
vermis, medial cerebellum. Loops around tonsils
AICA:
anterolateral cerebellum.
Labyrinthine a.:
off AICA in 85%, basilar in 15%.
SCA:
supplies deep nuclei
Superior
Sagittal Sinus: to Right transverse sinus (inferior
SS to Left)
Trolard:
to SSS. Labbe to transverse sinus
Deep
veins: Anterior caudate + terminal vv. >
Thalamostriate + septal (anterior) + epithalamic + atrial/ choroidal vv. >
Internal cerebral v. (at venous angle) + Basal v Rosenthal > VOG.
Basal Vein of Rosenthal:
ambient cistern
Thalamostriate v. :
injury results insomnolence, hemiparesis, & mutism (not seizures).
Posterior fossa Vv.:
Ant-Post: Precentral cerebellar v.,
Adamkiewicz:
Left T11 (T4-T8 most vulnerable to low flow)
Persistent
fetal arteries: Persistent
trigeminal: 0.1-0.5%, cavernous
Revised 6/1/09
Text Copyright 2009
Please
send comments and corrections to admin@flotte2.com
Disclaimer:
This outline is complied, not original. Sources are being added
retrospectively.
It is
intended for personal educational use by students and residents. It is not intended to guide clinical decision
making. Accuracy and timeliness cannot be guaranteed.
![]()